National Park Service

U.S. Department of the Interior

Natural Resource Stewardship and Science

Bandelier National Monument

Geologic Resources Inventory Report

Natural Resource Report NPS/NRSS/GRD/NRR—2015/1036
ON THE COVER: In the lower part of Frijoles Canyon, layered red rock crops out along the Falls Trail. These are 

maar deposits, created where rising magma interacted with water associated with the ancestral Rio Grande 

about 3 million years ago. A massive lava flow and river gravels overlie these colorful beds. National Park Service 

photograph, available at https://www.flickr.com/photos/bandeliernps/4748553919/ (accessed 26 December 2014). 

THIS PAGE: The Tshirege Member of the Bandelier Tuff, shown here at Long House in Frijoles Canyon, contains 

natural cavities that ancient people further excavated, making cavates for habitation and storage.

Photograph © George H. H. Huey.
Bandelier National Monument

Geologic Resources Inventory Report

Natural Resource Report NPS/NRSS/GRD/NRR—2015/1036

Katie KellerLynn 

Colorado State University Research Associate

National Park Service Geologic Resources Division

Geologic Resources Inventory

PO Box 25287

Denver, CO 80225

September 2015

U.S. Department of the Interior

National Park Service

Natural Resource Stewardship and Science 

Fort Collins, Colorado
ii

The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a 

range of reports that address natural resource topics. These reports are of interest and applicability to a broad audience 

in the National Park Service and others in natural resource management, including scientists, conservation and 

environmental constituencies, and the public. 

The Natural Resource Report Series is used to disseminate comprehensive information and analysis about natural 

resources and related topics concerning lands managed by the National Park Service. The series supports the 

advancement of science, informed decision-making, and the achievement of the National Park Service mission. The 

series also provides a forum for presenting more lengthy results that may not be accepted by publications with page 

limitations.

All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically 

credible, technically accurate, appropriately written for the intended audience, and designed and published in a 

professional manner. This report received informal peer review by subject-matter experts who were not directly 

involved in the collection, analysis, or reporting of the data.

Views, statements, findings, conclusions, recommendations, and data in this report do not necessarily reflect views and 

policies of the National Park Service, U.S. Department of the Interior. Mention of trade names or commercial products 

does not constitute endorsement or recommendation for use by the U.S. Government. 

This report is available from the Geologic Resources Inventory website (http://go.nps.gov/gripubs), and the Natural 

Resource Publications Management website (http://www.nature.nps.gov/publications/nrpm/). To receive this report in 

a format optimized for screen readers, please email irma@nps.gov.

Please cite this publication as:

KellerLynn, K. 2015. Bandelier National Monument: Geologic resources inventory report. Natural Resource Report 

NPS/NRSS/GRD/NRR—2015/1036. National Park Service, Fort Collins, Colorado.

NPS 315/129825, September 2015
iii

Contents

Page

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Products and Acknowledgments . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

GRI Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

Geologic Setting and Significance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Geologic Features and Processes . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Volcanic Rocks and Volcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Jemez Mountains Volcanic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Bandelier Tuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Features in Bandelier Tuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Rio Grande Rift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Cerros del Rio Volcanic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Lithic Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

El Cajete Pyroclastic Beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Paleontological Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

High-Elevation Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Galisteo Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Geologic Resource Management Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Fires, Fluvial Geomorphology, and Slope Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Cliff Retreat and Rockfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Seismic Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Cavate Deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Volcano Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Cochiti Dam and Reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Disturbed Land Restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Paleontological Resource Inventory, Monitoring, and Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Geologic History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Rio Grande Rift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Peripheral Volcanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Jemez Mountains Volcanic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Landscape Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Humans on the Landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Geologic Map Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Geologic Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Source Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

GRI GIS Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

GRI Map Poster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Map Unit Properties Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Use Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Additional References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Geology of National Park Service Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

NPS Resource Management Guidance and Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
iv

Contents (continued)

Page

Climate Change Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Geological Surveys and Societies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

US Geological Survey Reference Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Appendix A: Scoping Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2005 Scoping Meeting Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2014 Conference Call Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Appendix B: Geologic Resource Laws, Regulations, and Policies . . . . . . . . . . . . . . . . . . . . . . . . . 75

GRI Poster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .in pocket

Map Unit Properties Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .in pocket
v

Figures

Figure 1. Geologic time scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Figure 2. Photograph of Bandelier Tuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 3. Photograph of Tshirege Member cliff face . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 4A. Map of Bandelier National Monument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 4B. Map of Frijoles Canyon in Bandelier National Monument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 5. Schematic illustration of volcano types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 6. Satellite imagery of Bandelier National Monument and vicinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 7. Digital elevation model of the Jemez Mountains volcanic field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 8. Model of resurgent caldera formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 9. Geologic sketch of the Pajarito Plateau . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 10. Stratigraphic column for Bandelier Tuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 11. Photograph of Tshirege Member of Bandelier Tuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 12. Photograph of trail in Bandelier Tuff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 13. Photograph of petroglyphs at Tsankawi Mesa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 14. Photograph of tent rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 15. Map of the Rio Grande rift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 16. Schematic illustration of a normal fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 17. Schematic illustration of surface expressions of deformation within normal fault zones . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 18. Photographs of a Cerros del Rio cinder cone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 19. Schematic illustration of a maar explosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 20. Photograph of maar and lava flow in Frijoles Canyon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 21. Photograph of Upper Frijoles Falls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 22. Photograph of paleocanyon of the Rio Grande . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 23. Map of lithic resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 24. Photograph of obsidian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 25. Photograph of dacite quarry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 26. Photograph of El Cajete pyroclastic beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 27. Photograph of felsenmeer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 28. Map of fire extents at Bandelier National Monument. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 29. “Before” and “after” photographs of El Rito de Los Frijoles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Figure 30. Photograph of post-fire incision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 31. Photographs of effects of fire in Frijoles Canyon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 32. Map of Capulin Canyon watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 33. Photographs of Falls Trail in Lower Frijoles Canyon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure 34. Photographs of landscape recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 35. Schematic illustrations of slope movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Figure 36. Schematic illustration of volcano hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Figure 37. Photograph of Valle Grande. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Figure 38. Geologic sketch map of Valles caldera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Page

Tables

Page

Table 1. Classification and characteristics of volcanic rocks . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 2. Data layers in the Bandelier National Monument GRI GIS data set . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

vii

Executive Summary

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National Park Service 

(NPS) Inventory and Monitoring Program. The Geologic Resources Division of the NPS Natural 

Resource Stewardship and Science Directorate administers the GRI. This report synthesizes discussions 

from a scoping meeting for Bandelier National Monument (New Mexico) on 13–14 July 2005 and a 

follow-up conference call on 3 July 2014, which were held by the Geologic Resources Division to identify 

geologic resources of significance and geologic resource management issues, as well as determine the 

status of geologic mapping. It is a companion document to previously completed GRI GIS data.

Bandelier National Monument is a physiographic 

meeting place, incorporating major features of the 

Jemez Mountains volcanic field, Rio Grande rift, 

Cerros del Rio volcanic field, and Rio Grande (river) 

in an environment where human beings have acted as 

a central organism. Bandelier National Monument is 

situated in the Jemez Mountains volcanic field, where 

bowl-like Valles caldera takes center stage in location 

and importance. It is the world’s premier example 

of a resurgent caldera—a giant circular volcano with 

an uplifted central floor. The name “Valles” reflects 

the many spectacular valleys within the caldera; Valle 

Grande is the largest. 

The Rio Grande rift is also of physiographic significance 

for the monument. A series of nine basins, including the 

Española basin, make up the rift that is characterized 

by east–west crustal extension, forming grabens (faultbounded basins) that drop down along normal faults as 

Earth’s crust pulls apart. Bandelier National Monument 

is on the western side of the Española basin. The 

Pajarito fault zone, which is composed of normal faults 

and runs through the monument, bounds the Española 

basin. 

As a consequence of extension, Earth’s crust thinned 

within the Rio Grande rift, allowing heat from 

Earth’s mantle to reach the surface. Volcanism in the 

monument and vicinity occurred in connection with the 

development of the rift. For example, basaltic to dacitic 

lava erupted from vents in the Cerros del Rio volcanic 

field, which is at the edge of the Española basin. 

Frijoles and other canyons in the monument preserve 

evidence of this volcanic activity peripheral to the Jemez 

Mountains volcanic field.

The monument is east of the 24-km- (15-mi-) wide 

Valles caldera on the eastward–sloping Pajarito Plateau, 

which is cut by many canyons. Canyons that cross the 

monument are—from north to south—Chaquehui, 

Frijoles, Lummis, Alamo, Capulin, Medio, and Sanchez. 

These canyons are tributaries to the Rio Grande, 

which flows through White Rock Canyon along the 

southwestern edge of the monument. The river cut this 

steep-walled canyon, though notably, the river itself 

did not excavate the Rio Grande rift. Rather, the river 

follows a topographically lowest path within the rift. 

Its precursor, the ancestral Rio Grande, helped to fill 

the Española basin with sediment that the modern Rio 

Grande now erodes.

This GRI report was written for resource managers to 

support science-informed decision making, but it may 

also be useful for interpretation. Report preparation 

used available geologic information, and the NPS 

Geologic Resources Division did not conduct any new 

fieldwork in association with this report. Sections of 

the report discuss distinctive geologic features and 

processes at Bandelier National Monument, highlight 

geologic issues facing resource managers, describe the 

geologic history leading to the present-day landscape, 

and provide information about the GRI GIS data set. A 

poster (in pocket) illustrates these data. The Map Unit 

Properties Table (in pocket) summarizes report content 

for each geologic map unit within the monument.

The geologic features and processes of primary interest 

at Bandelier National Monument include the following:

● Volcanic Rocks and Volcanoes. Volcanic rocks 

include basalt, andesite, dacite, and rhyolite, with 

increasing amounts of silica, from less than 52% to 

more than 72%. The percentage of silica influences 

many properties of magma, including viscosity and 

explosiveness, which in turn influences the type 

of volcano these magmas produce. The volcano 

that created the landscape of Bandelier National 

Monument was rhyolitic, which is generally the 

most explosive type in the world.
viii

● Jemez Mountains Volcanic Field. Bandelier 

National Monument is on the eastern flank of the 

Jemez Mountains, where volcanism began about 14 

million years ago. The Valles and Toledo calderas 

are notable features of the field. The field contains 

volcanic rocks with a wide range of chemical 

compositions and eruption styles. The rocks of the 

Jemez Mountains volcanic field are divided into two 

major groups—Keres and Tewa. The Keres Group 

covers the pre-caldera part of the volcanic field 

and formed about 14 million to 1.8 million years 

ago. The Tewa Group covers the Toledo and Valles 

caldera complex, which developed from about 1.85 

million to 40,000 years.

● Bandelier Tuff. The eruptions that created the 

Toledo and Valles calderas are the most dramatic 

volcanic events to have occurred in New Mexico 

in the recent geologic past (Quaternary Period or 

the last 2.6 million years of geologic time). These 

events deposited two members of Bandelier Tuff. 

The Otowi Member (map unit Qbo) formed during 

collapse of the Toledo caldera about 1.61 million 

years ago. The Tshirege Member (Qbt) formed 

during the collapse of the Valles caldera about 1.25 

million years ago. Before eruption of the Otowi 

Member, leakage from the Bandelier magma 

chamber extruded the La Cueva Member about 

1.85 million years ago. The La Cueva Member is not 

included in the GRI GIS data. During each calderaforming eruption, rhyolitic magma blasted into the 

air, spreading ash across the landscape. Then, as the 

eruption column collapsed, pyroclastic flows sped 

away from the subsiding calderas. 

● Features in Bandelier Tuff. Layers of Bandelier 

Tuff are beautifully exposed in the canyon walls 

of the monument. The tuff hosts many features, 

some of which have cultural significance, including 

cavates (hollowed-out chambers by ancestral 

Puebloans) and an ancient trail system that is still 

used today. Conical, teepee-shaped landforms, 

locally called “tent rocks,” occur in all three 

members of Bandelier Tuff. 

● Rio Grande Rift. In the western part of Bandelier 

National Monument, the Bandelier Tuff is cut 

by the Pajarito fault zone, which delineates the 

active western margin of the Rio Grande rift. In 

Frijoles Canyon, the 1.25-million-year-old Tshirege 

Member is displaced about 145 m (480 ft) along the 

fault zone, creating a notable escarpment. Rocks of 

the Santa Fe Group fill the rift. 

● Cerros del Rio Volcanic Rocks. Cerros del Rio 

volcanic rocks (QTcrv), which are mostly basaltic, 

are well exposed in Bandelier National Monument. 

Particularly fine examples of a cinder cone, maar 

volcano (generated from the interaction of rising 

magma with water near Earth’s surface), and 

resistant lava flows, over which waterfalls now 

cascade, crop out in Frijoles Canyon. Cerros del 

Rio lavas erupted between about 2.7 million and 

1.1 million years ago. Late-stage volcanism in the 

Cerros del Rio volcanic field field produced dacite 

domes and flows, which were sources of lithic 

resources.

● Lithic Resources. The volcanic Jemez Mountains 

were a source of lithic resources such as obsidian, 

dacite, and chert, for the people living on the 

Pajarito Plateau. They used these materials to 

manufacture tools and projectile points. 

● El Cajete Pyroclastic Beds. Eruption of the El 

Cajete vent in the southern part of the Valles 

caldera about 55,000 years ago produced 

pyroclastic beds (Qvec), which are rich in pumice. 

Beginning in the 1200s, ancestral Puebloans began 

to settle on these pumice deposits, which have 

moisture-trapping capabilities, thus enabling 

farming on the slopes of the Jemez Mountains for 

nearly 500 years.

● Paleontological Resources. Published reports of 

Holocene fossils at Bandelier National Monument 

describe a 3,000-year-old packrat (Neotoma spp.) 

midden, and 8,000-year-old charcoal, wood, and 

cones of Douglas-fir (Pseudotsuga menziesii) in 

unconsolidated deposits in Frijoles Canyon. Fossils 

also may occur in unconsolidated Quaternary 

deposits (Qp2, 3, 4; Qa2, 3, 4; Qt; Qpa, Qa5; and 

Qfa). Also, ash deposits of Bandelier Tuff (Qbo and 

Qbt) may contain fossils. The most likely rock units 

to contain fossils are the Galisteo Formation (Tgs) 

and Santa Fe Group (Tesuque Formation, Tstc and 

Tstb; Chamita Formation Tscv; and axial channel 

facies, QTsfa). No fossils from these rock units have 

been reported from the monument to date, but 

elsewhere they are known to yield fossils. 

● High-Elevation Features. Boulder fields (Qrx) 

were mapped at high elevations in Bandelier 

National Monument. These features have 

characteristics of rock glaciers, which move by 

interstitial ice or ice cores. Other high-elevation 

features are patterned ground (asymmetrical 

circles, polygons, or stripes created by frost action) 
ix

and felsenmeer (German for “sea of rocks,” also 

created by frost action). 

● Galisteo Formation. The oldest rocks in Bandelier 

National Monument are 56 million–34 million 

years old (Eocene Epoch), and comprise the 

Galisteo Formation (Tgs). Unlike other bedrock 

in the monument, which is volcanic, the Galisteo 

Formation was deposited by rivers, long before the 

Jemez Mountains volcanic field came into existence 

and the Rio Grande flowed across the landscape.

Geologic resource management issues identified during 

the GRI scoping meeting and follow-up conference call 

include the following:

● Fires, Fluvial Geomorphology, and Slope 

Movements. Fire has tremendous effects on the 

landscape at Bandelier National Monument. It is 

a driving component in an interconnected system 

that includes streamflow, sediment transport, 

stream channel morphology, and slope movements. 

After fires, peak storm-water flow increases, 

sediment transport increases, stream channel 

geometry changes, and debris flows occur.

● Cliff Retreat and Rockfall. Bandelier Tuff 

dominates the landscape at Bandelier National 

Monument. The combination of welded and 

nonwelded layers promotes differential weathering, 

resulting in vertical cliffs and talus-covered slopes 

comprising canyon walls. Cliff retreat occurs by 

a combination of small rockfalls from cliffs (the 

most common type of slope movement in the 

monument); detachment of rocks from slopes; 

and larger, deep-seated landslides. The cliffs above 

the headquarters area, Main Loop Trail, and the 

“big curve” along the monument road are areas of 

concern with rockfall hazards.

● Seismic Activity. The Pajarito fault zone runs 

through Bandelier National Monument. The most 

recent surface-rupturing earthquake on the fault 

zone occurred between 2,200 and 1,400 years 

ago; no historic surface-rupturing earthquakes 

have occurred. The most recent relatively large 

earthquake in the area with strong local effects 

occurred in 1918. Earthquake magnitude and 

recurrence intervals along the Pajarito fault zone 

are poorly constrained, but available data suggest 

that earthquakes of magnitude 6.5 to 7 may occur at 

intervals of 10,000 to 60,000 years. The probability 

of a moderate earthquake (magnitude 5.0 or 

greater) occurring in the next century and affecting 

the monument is more than 50%.

● Cavate Deterioration. An understanding of the 

composition of the Bandelier Tuff into which 

cavates were excavated is important for managing 

these cultural resources. Preliminary geomorphic 

assessment of cavates and cliff bases in Frijoles 

Canyon found that deterioration of the tuff occurs 

mostly through small-scale spalling and granular 

erosion and to a lesser degree from rockfall. 

Discharge of water from the vadose zone at the cliff 

base, capillary rise of moisture into the tuff, and 

surface-water flow down cliff faces are the primary 

processes contributing to deterioration. 

● Volcano Hazards. Another huge caldera-forming 

eruption in the Jemez Mountains volcanic field is 

unlikely. Far more probable are smaller, but still 

potentially explosive, eruptions similar to those that 

occurred in Valles caldera 60,000–40,000 years ago. 

Possible hazards include the construction of a lava 

dome in the caldera, ash fall, ejection of bombs, and 

local pyroclastic flows down drainages.

● Cochiti Dam and Reservoir. Cochiti Dam is 10 

km (7 mi) downstream from Bandelier National 

Monument. It holds water and sediment from 

the Rio Grande (river) to form Cochiti Reservoir. 

Temporary flooding of about 140 ha (350 ac) of 

NPS lands upstream of the dam during the spring 

runoff period is allowed under a memorandum of 

understanding (MOU) between the National Park 

Service and US Army Corps of Engineers. Flooding 

has exceeded “temporary” time frames and created 

problems not anticipated by the MOU signatories, 

including reactivation of landslides (Qls). Another 

issue is that the reservoir is slowly filling with 

sediment via a process referred to as “silting.” 

Silting impacts monument resources as a result of 

burial of riparian areas and providing a favorable 

medium for pioneer plant succession, including 

agricultural weeds and riparian exotics.

● Disturbed Land Restoration. In 2005, GRI 

scoping participants identified sites in the 

amphitheater area in possible need of restoration. 

A former landfill is immediately south of the 

amphitheater; a former dump site is west of the 

landfill. Preliminary assessment and inspection of 

these sites in 2012 concluded that municipal waste 

was the primary component, and contaminants, 

though present, do not exceed background mean 

concentrations for New Mexico. These sites remain 

in place.
x

● Paleontological Resource Inventory, Monitoring, 

and Protection. Tweet et al. (2009) compiled 

paleontological information for the Southern 

Colorado Plateau Network, including Bandelier 

National Monument, but did not conduct a fieldbased inventory. Managers at Bandelier National 

Monument are encouraged to contact the NPS 

Geologic Resources Division for assistance with 

such an inventory, which would provide detailed, 

site-specific descriptions and resource management 

recommendations.
xi

Products and Acknowledgments

The NPS Geologic Resources Division partners with institutions such as Colorado State University, 

the US Geological Survey, state geological surveys, local museums, and universities to develop GRI 

products. This chapter describes those products and acknowledges contributors to this report.

GRI Products

The objective of the Geologic Resources Inventory is 

to provide geologic map data and pertinent geologic 

information to support resource management and 

science-informed decision making in more than 

270 natural resource parks throughout the National 

Park System. To realize this objective, the GRI team 

undertakes three tasks for each natural resource park: 

(1) conduct a scoping meeting and provide a summary 

document, (2) provide digital geologic map data in a 

geographic information system (GIS) format, and (3) 

provide a GRI report (this document). These products 

are designed and written for nongeoscientists.

Scoping meetings bring together park staff and geologic 

experts to review and assess available geologic maps, 

develop a geologic mapping plan, and discuss geologic 

features, processes, and resource management issues 

that should be addressed in the GRI report. Following 

the scoping meeting, the GRI map team converts the 

geologic maps identified in the mapping plan to digital 

geologic map data in accordance with the GRI data 

model. After the map is completed, the GRI report team 

uses these data, as well as the scoping summary and 

additional research, to prepare the GRI report. 

The compilation and use of natural resource 

information by park managers is called for in the 1998 

National Parks Omnibus Management Act (section 

204), 2006 National Park Service Management 

Policies, and the Natural Resources Inventory and 

Monitoring Guideline (NPS-75). The “Additional 

References” chapter and Appendix B provide links to 

these and other resource management documents and 

information.

Additional information regarding the GRI, including 

contact information, is available at http://go.nps.gov/gri. 

The current status and projected completion dates of 

products are available at http://go.nps.gov/gri_status.

Acknowledgments

The GRI team would like to thank the participants of 

the 2005 scoping meeting and 2014 conference call (see 

Appendix A) for their assistance with this inventory. 

Thanks very much to Fraser Goff (New Mexico Bureau 

of Geology and Mineral Resources) for his expertise 

and technical review of this report, which greatly 

improved its accuracy and content. In addition, thanks 

to Brian Jacobs and Barbara Judy (Bandelier National 

Monument), who provided references and answered 

questions during the report-writing process. Trista 

Thornberry-Ehrlich (Colorado State University) 

created many graphics for this report, in particular, the 

modified resurgent-caldera model (fig. 8) and updated 

Bandelier Tuff stratigraphy (fig. 10). Elaine Jacobs (Los 

Alamos National Laboratory) gave us a much-needed 

photograph of obsidian (fig. 24). We thank Kay Beeley

(Bandelier National Monument) for her help during 

the review process: she followed up with park staff and 

researchers, provided photographs, received permission 

to use photographs, and supplied review comments. 

Thanks to Jamie Civitello (Valles Caldera National 

Preserve) for furnishing information about lithic 

resources, and for knowing that basalt and dacite are 

different rocks. We thank Shari Kelley (New Mexico 

Bureau of Geology and Mineral Resources) for her 

clarification of the rocks in the Keres Group. Thanks to 

Gina D’Ambrosio (New Mexico Bureau of Geology 

and Mineral Resources) for providing photographs 

from bureau publications. Eric Bilderback (NPS 

Geologic Resources Division) reviewed the “Fires, 

Fluvial Geomorphology, and Slope Movements” 

section. Thanks very much to Stephen Monroe (NPS 

Southern Colorado Plateau Network) for his input on 

the effects of the Las Chonchas Fire in the monument.

And, finally, thanks to George H. H. Huey and Lauren 

Blauert (George H. H. Huey Photography, Inc.) for 

licensing use of the inside cover image.

Review

Kay Beeley (Bandelier National Monument)

Fraser Goff (New Mexico Bureau of Geology and 

Mineral Resources)

Jason Kenworthy (NPS Geologic Resources Division)
xii

Stephen Monroe (NPS Southern Colorado Plateau 

Network)

Harold (Hal) Pranger (NPS Geologic Resources 

Division)

Editing

Rebecca Port (NPS Geologic Resources Division)

Report Formatting and Distribution

Jason Kenworthy (NPS Geologic Resources Division)

Rebecca Port (NPS Geologic Resources Division)

Source Maps

New Mexico Bureau of Geology and Mineral Resources

US Geological Survey

GRI Digital Geologic Data Production

Derek Witt (Colorado State University)

James Chappell (Colorado State University)

Stephanie O’Meara (Colorado State University)

GRI Map Poster Design

Georgia Hybels (Colorado State University)

GRI Map Poster Editing

Georgia Hybels (Colorado State University)

Rebecca Port (NPS Geologic Resources Division)

Jason Kenworthy (NPS Geologic Resources Division)
1

Geologic Setting and Significance

This chapter describes the regional geologic setting of Bandelier National Monument and summarizes 

connections among geologic resources, other park resources, and park stories.

Bandelier National Monument is a volcanology 

mecca—a “must see” destination for geologists, 

volcanologists, and volcano aficionados. The 

monument hosts a premier example of an ash-flow tuff, 

which is quite possibly the world’s most famous (see 

“Bandelier Tuff” section). The tuff, which dominates 

the monument’s landscape, represents caldera-forming 

eruptions that are of a scale never witnessed by humans 

(Dunbar 2005). Researchers and educators come to 

the monument to see the Bandelier Tuff because of 

its extensive exposures and the volcanic features it 

preserves.

Many of the seminal papers and maps published in 

the 1960s about volcanism feature Bandelier National 

Monument and vicinity. These publications include 

work by US Geological Survey (USGS) geologists, in 

particular, R. L. Smith and R. A. Bailey, along with their 

colleague C. S. Ross. Smith, Bailey, and Ross began 

mapping the Valles caldera in 1938, finishing in 1970 

(see “Valles Caldera” section).

Although remapped since that time (see “Geologic Map 

Data” chapter), the Smith et al. (1970) map serves as a 

benchmark for the study of volcanism around the globe. 

Moreover, the famous paper “Resurgent Cauldrons” by 

Smith and Bailey (1968) presented a seven-stage model 

for caldera formation. This model, hypothesized at the 

monument and vicinity, has stood the test of time and 

is still taught in classrooms today (see “Valles Caldera” 

section). 

Over the years, geologists have combined and 

subdivided the rocks of the Jemez Mountains volcanic 

field into various formations and groups. It is now 

divided into two major groups of rocks—Keres and 

Tewa. The Keres Group represents the pre-caldera 

portion of the Jemez Mountains volcanic field and 

consists of domes, flows, tuffs, and associated sediments 

that started erupting onto the landscape about 14 

million years ago (Gardner et al. 2010; Goff et al. 2011; 

Kelley et al. 2013). The Tewa Group represents the 

Valles–Toledo caldera complex that produced the 

Bandelier Tuff, starting about 1.85 million years ago 

(Quaternary Period, Pleistocene Epoch; fig. 1). The 

Tewa Group includes rhyolite domes and lava flows, 

small- and large-volume pyroclastic flows, ash fall, and 

a variety of volcaniclastic deposits. The last of the Tewa 

Group was deposited 45,000–34,000 years ago as the 

Banco Bonito flows in Valles caldera. 

The terms “Keres” and “Tewa” have geological, 

geographical, and cultural significance. Keres rocks 

were named by Bailey et al. (1969) for the Keresan 

Range—an old name for this part of the Jemez 

Mountains. Keres is also the name of a Pueblo language. 

Around the area today, Keres speakers, like the rocks of 

the same name, are to the south, which was also likely 

true in the past (Leahy 1999). Another Pueblo language 

is Tewa, with speakers in the north. Tradition holds that 

Frijoles Canyon—a notable canyon for its geological 

and archeological resources in the monument—was the 

dividing line between Keres and Tewa language groups. 

Some native speakers say that the name “Tyuonyi” 

(for the pueblo in Frijoles Canyon) means a “place 

of meeting” or “place of treaty” (Leahy 1999). Griggs 

(1964) chose the name “Tewa” for the rocks that cover 

this area of the Jemez Mountains. 

Bandelier Tuff is divided into three members—La 

Cueva, Otowi, and Tshirege. The Tshirege Member 

dominates the landscape of the monument, making up 

the mesas and canyon walls (fig. 2). Weathering and 

erosion of the softer layers of this member led to the 

Swiss-cheese appearance of some of the cliffs (fig. 3). 

Ancestral Puebloans (ancestors of today’s Pueblo and 

Hopi people, and commonly called Anasazi in earlier 

literature) enlarged many of these holes for living and 

storage. Frijoles Canyon is a notable locale for these 

particular cliff dwellings, called “cavates,” which are 

inexorably tied to the Bandelier Tuff. 

Frijoles Canyon is a small part of an extensive area 

once inhabited by ancestral Puebloans. Villages were 

scattered throughout the surrounding Pajarito Plateau 

and Rio Grande valley. At times, members of this 

far-flung culture inhabited parts of Colorado, Utah, 

Arizona, and New Mexico. Their ancient homes can 

be seen in places such as Mesa Verde National Park 

(see GRI report by Graham 2006), Canyon de Chelly 
2

National Monument (see GRI scoping summary 

by KellerLynn 2007), and Chaco Culture National 

Historical Park (see GRI report by KellerLynn 2015). 

In 1880, people from the Cochiti Pueblo brought 

anthropologist Adolph Bandelier to Frijoles Canyon 

to see the place they consider their ancestral home. 

Bandelier was impressed and in 1890 wrote his classic 

novel, The Delight Makers, which is set in Frijoles 

Canyon among the ancestral people who lived there. 

Bandelier returned four times to the place that would 

become named in his honor (Barey 1990). 

In 1916, Bandelier National Monument was established 

by presidential proclamation to protect and preserve 

for public enjoyment and education the large Pueblo 

settlements and spectacular cliff dwellings of the 

southern Pajarito Plateau. At that time, the monument 

and its archeological resources enjoyed considerable 

national prominence both in the public eye and within 

the discipline of archeology, largely as a result of the 

pioneering explorations of Adolph Bandelier and the 

later excavations and preservation efforts of Edgar L. 

Hewett (Toll 1995).

Bandelier National Monument consists of two 

noncontiguous units, a main unit and Tsankawi Section 

(fig. 4). Both units of the monument are amidst vast 

areas of open space. The northeastern boundary of 

the main unit is adjacent to Los Alamos National 

Laboratory, which covers 10,700 ha (26,500 ac); public 

access is restricted on these Department of Energy 

lands. To the northwest is Valles Caldera National 

Preserve—a multiuse nature preserve that incorporates 

most of the caldera and consists of 36,000 ha (88,900 

ac) of grasslands and forests. In December 2014, the 

preserve was authorized as a unit of the National Park 

System. In addition, more than 405,000 ha (1 million ac) 

of the Santa Fe National Forest surround the main unit, 

including the Dome Wilderness, which is administered 

by the US Forest Service and is adjacent to the Bandelier 

Wilderness within Bandelier National Monument. 

About 70% of the monument is designated wilderness. 

The southern boundary of the monument is contiguous 

with lands owned by the New Mexico State Lands 

Office. NPS lands adjacent to the Rio Grande include an 

easement granted to the US Army Corps of Engineers 

for the operation of Cochiti Dam and Reservoir.

Tsankawi takes its name from Tsankawi Pueblo, a 

major archeological pueblo or village, containing 

about 275 ground-floor rooms. Tsankawi encompasses 

approximately 300 ha (800 ac) northeast of the main 

unit. Tsankawi sits atop a mesa formed by Sandia 

Canyon on the south and Los Alamos Canyon on the 

north and has a commanding view in all directions. 

Tsankawi is nearly surrounded by Los Alamos National 

Laboratory with tribal lands of the San Ildefonso 

Pueblo adjoining on the south and east.

Figure 1 (facing page). Geologic time scale. The divisions of the geologic time scale are organized stratigraphically, 

with the oldest divisions at the bottom and the youngest at the top. GRI GIS map abbreviations for each time division 

are in parentheses. Compass directions in parentheses indicate the regional locations of events. Boundary ages are 

millions of years ago (MYA). Time periods with orange text are represented in the GRI GIS map data for Bandelier 

National Monument. The oldest rocks exposed in the monument are from the Eocene Epoch (E). Volcanic activity 

in the Jemez Mountains volcanic field has been ongoing since the Miocene Epoch (MI). Pliocene (PL) Cerros del Rio 

volcanic rocks in the monument host notable features such as a cinder cone and maar volcano. Bandelier Tuff erupted 

as ash fall and pyroclastic flows during the Pleistocene Epoch (PE). National Park Service graphic using dates from the 

International Commission on Stratigraphy (http://www.stratigraphy.org/index.php/ics-chart-timescale; accessed 6 April 

2015).
3

Formation of the Earth

Eon Era Period Epoch MYA Phanerozoic Proterozoic Archean Hadean Cenozoic (CZ) Mesozoic (MZ) Paleozoic (PZ)

Quaternary

(Q)

Neogene

(N)

Cretaceous (K)

Jurassic (J)

Triassic (TR)

Permian (P)

Pennsylvanian (PN)

Mississippian (M)

Devonian (D)

Silurian (S)

Ordovician (O)

Cambrian (C)

Precambrian (PC, X, Y, Z)

Holocene (H)

Pleistocene (PE)

Pliocene (PL)

Miocene (MI)

Oligocene (OL)

Eocene (E)

Paleocene (EP)

2.6

5.3

23.0

33.9

56.0

145.0

201.3

298.9

323.2

358.9

419.2

443.8

485.4

2500

4000

4600

66.0

541.0

Age of Mammals Age of Reptiles Age of Amphibians Fishes Marine Invertebrates

Modern humans 

Spread of grassy

 ecosystems

Extinction of large

 mammals and birds 

Early primates 

Placental mammals 

Early flowering plants 

Dinosaurs diverse and

 abundant

First dinosaurs; first mammals

Flying reptiles

Sharks abundant

First reptiles

Mass extinction

First amphibians

First forests (evergreens)

First land plants

Mass extinction

Primitive fish

Trilobite maximum

Rise of corals

Complex multicelled organisms 

Simple multicelled organisms 

Early bacteria and algae

 (stromatolites)

Origin of life

0.01

Mass extinction

Paleogene

(PG)

Tertiary (T)

Basin and Range extension (W)

Elko Orogeny (W)

Breakup of Pangaea begins

Sonoma Orogeny (W)

Supercontinent Pangaea intact

Ouachita Orogeny (S)

Ancestral Rocky Mountains (W)

Antler Orogeny (W)

Acadian Orogeny (E-NE)

Taconic Orogeny (E-NE)

Extensive oceans cover most of 

 proto-North America (Laurentia)

First iron deposits

Abundant carbonate rocks

Formation of Earth’s crust

Oldest known Earth rocks

Formation of early supercontinent

Grenville Orogeny (E)

Cascade volcanoes (W)

Ice age glaciations;

 glacial outburst floods

Columbia River Basalt eruptions (NW)

Linking of North and South 

 America (Isthmus of Panama)

Laramide Orogeny ends (W)

Nevadan Orogeny (W)

Sevier Orogeny (W)

Laramide Orogeny (W)

Alleghany (Appalachian)

 Orogeny (E)

Supercontinent rifted apart

Western Interior Seaway (W)

Early shelled organisms

252.2 Mass extinction

 Life Forms North American Events 

Mass extinction

Coal-forming swamps
4

Figure 2. Photograph of Bandelier Tuff. The walls of Frijoles Canyon display colorful Bandelier Tuff, which consists 

of extensive ash falls and pyroclastic flows. The Tshirege Member makes up most of the canyon walls. National Park 

Service photograph.

Figure 3. Photograph of Tshirege Member cliff face. In Frijoles Canyon, the Tshirege Member forms cliff faces that 

resemble Swiss cheese. Ancestral Puebloans took advantage of the relatively soft nature of the tuff and its preexisting 

cavities to excavate cavates, which they inhabited between 1150 and 1550 CE (common era). Photograph by Katie 

KellerLynn (Colorado State University).
5

Bandelier Wilderness and

Dome Wilderness areas

Bandelier National

Monument boundary

Campground

Paved road

Four-wheel

drive road

Trail

0 1 2 3

0 1 2 3

4 Miles

4 Kilometers

North

Warning: Do not use these maps for backcountry travel. 

Obtain and use a current topographic map for wilderness 

hikes.

4

4

4

502

502

501

30

289

289

268

142

142

R I O G R A N D E

R I O G R A N D E

El Rito de los Frijoles (Frijoles Creek)

Apache Spring

Upper Frijoles 

Falls

Lower Frijoles

Falls

Turkey Springs

Cochiti

Lake

Alcove

House

Painted Cave

Yapashi

Tsankawi

See detail map at right

TSANKAWI SECTION

BANDELIER

NATIONAL MONUMENT

Visitor Center

BANDELIER

 NATIONAL

 MONUMENT Dome

Trailhead

COCHITI CANYON

SANCHEZ CANYON

CAPULIN CANYON ALAMO CANYON

HONDO CANYON

LUMMIS CANYON

MEDIO CANYON

W H I T E R O C K C A N Y O N

CAÑON DE LOS FRIJOLES

CAJA DEL RIO

PLATEAU

PAJARITO

MESA

J E M E Z

M

O

U

N

T A

I

N

S

BURNT MESA

LOS ALAMOS CANYON

SAN MIGUEL MOUNTAINS

(FRIJOLES CANYON)

Bland Canyon Road

Dome Road

St. Peters Dome Road

Pajarito Road

East Jemez Road

(closed in winter)

(closed in winter)

(closed in winter)

(closed in winter)

(truck route)

(closed to public)

(access may be restricted)

Sawyer Mesa

Trail

Upper

Frijoles

Canyon

Overlook

Trail

Apache Mesa Trail

Cerro Grande Trail

A al mo Boundary

Ponderosa Trail

West Alamo Rim Trail

Capulin Canyon Trail

Turkey Springs Trail

Mid- Alamo Trail

Burro Trail

Boundary Peak Trail

Stone Lions Trail

Frijoles Rim Trail

Burnt Mesa Trail

Trail

Frijoles Canyon Trail

(challenging due

to flooding)

Town of 

LOS ALAMOS

Town of 

WHITE ROCK

To Española

To Santa Fe

To Jemez

Springs

Gate

Gate

Gate

Gate

Cerro Grande

10199ft

3109m

5311ft

1619m

St Peters Dome

8463ft

2580m

Boundary Peak

8182ft

2494m

White Rock

Overlook

Pajarito Ski Area

Ponderosa

Group Campground

(reservations required)

7580ft

2310m

Juniper

Campground

White Rock

Visitor Center

Park Entrance Station

Upper

Crossing

7020ft

2140m

SANTA FE

NATIONAL

FOREST

SANTA FE

NATIONAL FOREST

VALLES CALDERA

NATIONAL

PRESERVE

SANTA FE

NATIONAL FOREST

DEPARTMENT OF

ENERGY

LOS ALAMOS NATIONAL

LABORATORY

PRIVATE LANDS

COCHITI INDIAN RESERVATION

SAN ILDEFONSO

INDIAN RESERVATION

BANDELIER WILDERNESS

DOME 

WILDERNESS

Figure 4A. Map of Bandelier National Monument. Bandelier National Monument protects approximately 13,300 

ha (33,000 ac) of canyon and mesa country in the Jemez Mountains of northwestern New Mexico. Canyons in the 

monument include Sanchez, Medio, Capulin, Hondo, Alamo, Lummis, and Frijoles (fig. 4B). The monument is composed 

of two units; Tsankawi is northeast of the main unit. Valles Caldera National Preserve, Santa Fe National Forest, and 

Los Alamos National Laboratory are principal neighbors, with New Mexico State Lands on the south and an easement 

with the US Army Corps of Engineers on the Rio Grande. National Park Service graphic.
6

Cliff Dwellings

Cliff Dwellings

Tyuonyi

Big Kiva

Frijolito

Alcove House

Visitor Center

Frey Trail Campground to

Visitor Center

2.0mi 3.2km

Tyuonyi Overlook

Trail

Dead-end trail—

does not connect

with any other trail

1.0mi 1.6km

Falls Trail

Main Loop Trail

Main Loop Trail

Falls Trail

Falls Trail

Backpacker

parking to:

Upper Falls

1.5 mi 2.4km

Reached by

140 foot climb

on four ladders 

(unexcavated)

(Long House)

(talus houses)

6066ft

1849m BANDELIER NATIONAL MONUME N T BOUNDARY

4

El Rito de los Frijoles (Frijoles Creek)

Entrance Road

Overlook

Park 

Entrance

Station

Tyuonyi Overlook

Juniper

Campground

6600ft

2012m

Coyote

Loop

Packrat

Lane

Abert’s

Squirrel

Loop

Black

Bear

Loop

Amphitheater

Picnic area & RV parking

Backpacker &

overflow parking

Parking

Gift Shop and

Snack Bar

C A

Ñ

O

N

D

E L O

S

F

R I J O L E S

( F R I J O L E S C A N Y O N )

To White Rock

and Santa Fe

To Los Alamos

and Jemez Springs

BANDELIER

NATIONAL

MONUMENT

Main Loop Trail

Alcove House Trail

Other trails

Paved road

0.1

0.1

0.2 Mile

0.2 Kilometer

North

0

0

Figure 4B. Map of Frijoles Canyon in Bandelier 

National Monument. National Park Service graphic.
7

Geologic Features and Processes

This chapter describes noteworthy geologic features and processes in Bandelier National Monument.

During the 2005 scoping meeting (see National Park 

Service 2005) and 2014 conference call, participants 

(see Appendix A) identified the following geologic 

features and processes of significance at Bandelier 

National Monument:

● Volcanic Rocks and Volcanoes

● Jemez Mountains Volcanic Field

● Bandelier Tuff

● Features in Bandelier Tuff

● Rio Grande Rift

● Cerros del Rio Volcanic Rocks

● Lithic Resources

● El Cajete Pyroclastic Beds

● Paleontological Resources

● High-Elevation Features

● Galisteo Formation

Volcanic Rocks and Volcanoes

Geologists use silica (silicon dioxide, SiO2) content as 

a means for classifying volcanic rocks (table 1). The 

amount of silica influences many properties of magma, 

including viscosity (internal friction) and explosiveness. 

In general, lavas with more silica are more viscous and 

more explosive. Flows of andesite (57%–63% SiO2) 

and dacite (63%–68% SiO2), for example, tend to 

be thick and sluggish, traveling only short distances 

from a vent (an opening at Earth’s surface through 

which magma erupts or volcanic gases are emitted). 

Dacite and rhyodacite (68%–72% SiO2

) lavas often 

squeeze out of a vent to form irregular mounds or lava 

domes. Two dacite domes—Sawyer Dome (Ttsd) and 

Cerro Grande (Ttcg)—are on the northern boundary 

Table 1. Classification and characteristics of volcanic rocks

Rock Name: Rhyolite Rhyodacite Dacite Andesite Basaltic 

Andesite

Basalt

Silica (SiO2) 

content1 >72% 68%–72% 63%–68% 57%–63% 52%–57% <52%

Color

Lighter Darker

Viscosity of 

magma

Thick

(less mobile flows)

Fluid

(more mobile flows)

Typical style of 

eruption Explosive Effusive

Eruption 

temperature2

Cooler, 800°C 

(1,500°F)

Hotter, 1,160°C 

(2,120°F)

1

Silica percentages from Clynne and Muffler (2010). 2Eruption temperatures from Price (2010).

Figure 5. Schematic illustration of volcano types. The 

size and shape of volcanoes are influenced by the 

amount of silica and gas in the erupting lava. Low-silica 

lavas, such as basalt, produce broad shield volcanoes 

(A). If basaltic lava has a lot of gas, a central vent 

may erupt like a fire hose, forming a cinder cone (B). 

Higher silica lavas, andesite to rhyolite, form composite 

volcanoes, also called “stratovolcanoes” (C). Lava domes 

form around a vent that erupts high-silica lava such as 

dacite (D). Graphic by Jason Kenworthy (NPS Geologic 

Resources Division) after Lillie (2005, figure 2.18).
8

of the monument. By contrast, low-silica basalts 

(<52% SiO2) form lava flows that spread out in broad, 

thin sheets up to several kilometers wide. Repeated 

eruptions of basaltic flows in a volcanic field may build 

a shield volcano (fig. 5). Individual eruptions of basalt 

commonly form cinder cones. A notable cinder cone, 

composed of Cerros del Rio volcanic rocks (QTcrv), 

occurs in Frijoles Canyon. 

The most explosive volcanoes on Earth are generally 

rhyolitic (>72% SiO2). After an eruption of rhyolite, 

volcano edifices often do not look like volcanoes 

because the eruptions are so explosive that the volcano 

ends up collapsing in on itself, creating a caldera. The 

eruption that formed Valles caldera was this type. It is 

the oldest of three young caldera-forming volcanoes 

in the United States; the others are Yellowstone in 

Wyoming and Long Valley in California (US Geological 

Survey 2014b). In addition to the Yellowstone caldera 

within the National Park System, the Bursum and 

Gila Cliff Dwellings calderas, which surround Gila 

Cliff Dwellings National Monument in New Mexico 

(see GRI report by KellerLynn 2014), are the result of 

rhyolitic explosions that took place about 28 million 

years ago.

Jemez Mountains Volcanic Field

Bandelier National Monument is on the eastern flank 

of the Jemez Mountains, which is the geographic 

expression of a volcanic field so large—72 km (45 mi) 

across—that it is best recognized in aerial photographs 

or satellite imagery (fig. 6). Displayed on geologic maps 

(see poster, in pocket) or digital elevation models (fig. 

7), distinctive features also “pop.”

Initial activity of the Jemez Mountains volcanic field 

exhibited a wide range of chemical compositions and 

eruption styles, from effusive basaltic (less than 53% 

SiO2

; table 1) to eruptive rhyolitic (more than 72% SiO2). 

Overall, andesite (57%–63% SiO2) is the dominant rock 

type in the Jemez Mountains volcanic field, though 

rhyolite, which represents the most recent eruptions, 

has come to characterize the “Bandelier type.” 

Valles Caldera

Valles caldera is at the center of the Jemez Mountains 

volcanic field. It is the world’s premier example of a 

resurgent cauldron or caldera—a giant circular volcano 

with an uplifted central floor (Goff et al. 2011). During 

the 1960s, R. L. Smith and R. A. Bailey published several 

widely recognized papers that summarized their many 

years of work in the region. Based on their study of 

Valles caldera, Smith and Bailey (1968) proposed a 

model of caldera formation that has served as the global 

standard for other calderas and facilitated recognition 

and understanding of calderas around the world 

(Goff et al. 2011). For example, Yellowstone was not 

recognized as a resurgent caldera until many years after 

the Valles model was studied, published, and applied to 

other suspects (Goff 2010). With minor modifications, 

the Smith and Bailey model has stood the test of time 

(Goff et al. 2011). Figure 8 presents a modified version 

of this model. 

Toledo Caldera

The Toledo caldera was created 1.61 million years ago 

during the first of two caldera-forming eruptions of 

Bandelier Tuff. The second caldera-forming eruption 

emplaced the Tshirege Member of Bandelier Tuff 

1.25 million years ago and created Valles caldera. 

Because the Toledo caldera was largely obliterated by 

the later Valles caldera, it is commonly overlooked 

and considerably less is known about it. The Tshirege 

Member filled the Toledo caldera, burying much of 

the preexisting rock. Nevertheless, the explosion that 

created the Toledo caldera was no less spectacular 

than the one that created the Valles caldera 400,000 

years later. Explosion of the Toledo volcano produced 

a giant cauldron roughly 14 km (9 mi) across. Each 

climactic eruption deposited an estimated 400 km3

 (100 

mi3) of material (Fraser Goff, New Mexico Bureau of 

Geology and Mineral Resources, volcanologist, written 

communication, 28 April 2015). 

Rocks of the Jemez Mountains Volcanic Field

Geologists have divided the rocks of the Jemez 

Mountains volcanic field into two major groups: Keres 

and Tewa. All volcanic and volcaniclastic rocks that 

are younger than 14 million years old but older than 

Bandelier Tuff belong to the Keres Group. All Bandelier 

Tuff and younger volcanic and volcaniclastic units 

belong to the Tewa Group (Gardner et al. 2010; Goff et 

al. 2011; Kelley et al. 2013). 

Keres Group

In Bandelier National Monument, rocks of the Keres 

Group include, from oldest to youngest, the Canovas 

Canyon Rhyolite (Tcct; 12 million–8 million years old), 

Paliza Canyon Formation (Tphd, Tppa, Tpdt, and Tpa; 

10 million–7 million years old), Bearhead Rhyolite (Tkpt
9

Figure 6. Satellite imagery of Bandelier National Monument and vicinity. Bandelier National Monument is in the 

Jemez Mountains volcanic field, which is marked by the stunning Valles caldera. The monument spreads across the 

Pajarito Plateau to the Rio Grande (river) that flows through White Rock Canyon. Caja del Rio and Santa Ana Mesa 

represent areas of peripheral volcanism adjacent to the Jemez Mountains volcanic field. Española basin to the east 

of the monument is part of the active Rio Grande rift. Dashed box indicates extent of detailed map. Graphic by Trista 

Thornberry Ehrlich (Colorado State University). Base imagery from ESRI ArcGIS World Imagery (accessed 11 February 

2015).
10

and Tbh; 7 million–6 million years old), and Tschicoma 

Formation (Ttsd, Ttcg, and Ttpm; 5 million–2 million 

years old). These rocks represent volcanic domes and 

lava flows of andesite, dacite, and rhyolite.

The resultant volcaniclastic material from erosion 

of these volcanic domes is also part of the Keres 

Group (Shari Kelley, New Mexico Bureau of Geology 

and Mineral Resources, field geologist, email 

communication, 18 May 2015). Erosion of the Bearhead 

Rhyolite domes is recorded in the volcaniclastic Cochiti 

Formation (QTc; 6.5 million–2 million years old), which 

formed as alluvial fans shed into the evolving Rio 

Grande rift (Goff and Gardner 2004). The fans consist 

of a pinkish-gray mixture of sands reworked out of the 

Santa Fe Group and volcanic rocks of the Keres Group 

(Kelley et al. 2013).

Similarly, erosion of domes of the Tschicoma Formation 

is preserved in the volcaniclastic Puye Formation 

(QTpt; Kelley et al. 2013). The Puye Formation is 

a “fanglomerate,” consisting of a huge alluvial fan 

complex that shed eastward from these volcanoes. 

In outcrops along the Rio Grande (river), the Puye 

Formation also contains basaltic debris derived from 

contemporaneous volcanism and erosion of the Cerros 

del Rio volcanic field (figs. 6 and 9). Development of 

the Cerros del Rio volcanic field may have significantly 

influenced deposition of the Puye Formation by 

effectively blocking the Rio Grande valley and imposing 

a major base level rise at the toe of the alluvial fan 

(Reneau and Dethier 1996; see “Cerros del Rio Volcanic 

Rocks” section). 

The Puye Formation ancestral Rio Grande facies (QTpt, 

slightly lithified pebble to cobble gravel) was deposited 

in the rift between 5.3 million and 2.6 million years ago 

(Pliocene Epoch; fig. 1). 

Tewa Group

Three formations comprise the Tewa Group: 

Bandelier Tuff, Cerro Toledo Formation, and Valles 

Rhyolite. These formations consist of the volcanic and 

volaniclastic rocks and deposits directly associated 

with the evolution and eruptions of the Toledo and 

Valles calderas (Gardner et al. 2010), including the 

two caldera-forming eruptions that deposited the 

Figure 7. Digital elevation model of the Jemez Mountains volcanic field. This image clearly illustrates the shape of 

Valles caldera; the striking, circular arrangement of rhyolitic domes within the caldera; and the radial pattern of 

drainages away from the rim. The flat area within the caldera is Valle Grande. Pajarito Plateau and Bandelier National 

Monument are on the right side of the crater rim. White Rock Canyon is at the base of the plateau. The impressive 

ridge to the west of the caldera is the Sierra Nacimiento. New Mexico Bureau of Geology and Mineral Resources 

graphic, available at https://geoinfo.nmt.edu/faq/volcanoes/ (accessed 21 May 2015).
11

Otowi (Qbo) and Tshirege (Qbt) members of 

Bandelier Tuff (see “Bandelier Tuff” section). In 

addition, large rhyolite domes such as Rabbit 

Mountain were emplaced in the Toledo caldera 

in between these two cataclysmic explosions. 

Rabbit Mountain rhyolite (Qcrm) is part of the 

Cerro Toledo Formation. Also, ash fall deposits 

(Qct; also called “pyroclastic fall deposits”), 

debris flow deposits (Qrd1), and colluvial deposits 

of reworked pumice and blocks of the Otowi 

Member (Pueblo Canyon Member; Qcpc) are part 

of the Cerro Toledo Formation and thus the Tewa 

Group. Finally, Valles Rhyolite is part of the Tewa 

Group and represents the most recent volcanism 

of the Jemez Mountains volcanic field (see 

“Volcano Hazards” and “Geologic History”). The 

youngest eruption occurred 45,000–37,000 years 

ago, extruding the Banco Bonito flows. These 

flows do not occur in the national monument, but 

other members of Valles Rhyolite, such as Qrd2, 

Qtoal, and Qvec, do.

Bandelier Tuff

Bandelier Tuff, which erupted in three episodes 

starting approximately 1.85 million years ago 

(Spell et al. 1996; Goff et al. 2011), is part of the 

Tewa Group. The two caldera-forming members 

of Bandelier Tuff—Otowi and Tshirege—began 

as “Plinian eruption” columns that rose rapidly 

into the air to heights exceeding 35 km (20 mi). 

Plinian eruptions are explosive and characterized 

by large amounts of tephra and a tall eruption 

column from which a steady, turbulent stream of 

fragmented magma and magmatic gas is released at 

a high velocity. These eruptions are documented in 

the rock record by ash fall (also called “pyroclastic 

fall”) deposits, and resulted in pumice strewn 

across the landscape.

Following the ash fall phase, the eruption column 

collapsed, resulting in pyroclastic flows (also 

Figure 8. Model of resurgent caldera formation. The Smith and Bailey (1968) model has survived the test of time with 

some modifications. Research since Smith and Bailey’s time has suggested that caldera-forming eruptions and caldera 

collapse occur simultaneously. Also, the timing of hydrothermal activity is now thought to begin earlier and is not 

considered “terminal” as represented by the original Smith and Bailey model. Much more is known about the timing 

of caldera collapse and resurgent uplift than was known in the 1960s. Phillips (2004) and Phillips et al. (2007) obtained 

many 40Ar/39Ar ages to determine the timing and duration of Valles caldera resurgence. These findings show that 

resurgence began within at most 54,000 years after caldera formation. Graphic by Trista Thornberry-Ehrlich (Colorado 

State University) after Smith and Bailey (1968, figure 5), Williams and Bacon (1988, topographic map with illustrations 

and diagrams), Goff (2009, figure 33), and Goff (2010, general model of caldera formation).
12

called “ash flows” or “ignimbrites”) spreading swiftly 

across the landscape. Pyroclastic flows are very hot, 

density currents composed of gases and pyroclastic 

material that radiate outward from a collapsing caldera 

at speeds of 80 to 320 kph (50 to 200 mph). Bandelier 

pyroclastic flows created the Pajarito Plateau and 

covered more than 21 km (13 mi) across the western 

Española basin.

As a result of work by Smith and Bailey, along with 

USGS colleague C. S. Ross (Smith and Bailey 1966; 

Bailey et al. 1969), the Bandelier Tuff became what is 

probably the world’s most famous ash-flow tuff (Goff 

2009). The term “Bandelier Rhyolite Tuff” was first used 

by H. T. U. Smith (1938, figure 4, p. 937), who mapped 

the tuff in the Abiquiu quadrangle, Rio Arriba County, 

north-central New Mexico, on the northern side of the 

Jemez Mountains. Today, geologists have subdivided the 

Bandelier Tuff into three formal members—La Cueva, 

Otowi, and Tshirege (fig. 10; Gardner et al. 2010; Goff et 

al. 2011; Kelley et al. 2013). 

La Cueva Member

The La Cueva Member consists of rhyolitic pyroclastic 

flows and ash fall that predate the Otowi Member; it 

has argon-40/argon-39 (40Ar/39Ar) ages of 1.85 ± 0.07 

and 1.85 ± 0.04 million years ago (Spell et al 1996). The 

La Cueva Member is volumetrically smaller than the 

other two members but lithologically very similar. Smith 

(1979) described the material as part of an early leakage 

of the Bandelier magma chamber. This preliminary 

eruption took place some 200,000 years before the 

formation of Toledo caldera and the eruption of the 

Otowi Member.

The La Cueva Member was previously called the San 

Diego Canyon ignimbrites by Self et al. (1986). In 

addition to San Diego Canyon, the La Cueva Member 

is found in the walls of Valles caldera, underlying 

Redondo Peak, as thin beds layered with the Puye 

Formation north of Los Alamos, and beneath the Otowi 

Member in the lower reaches of Alamo Canyon in 

Bandelier National Monument (Gardner et al. 2010). 

The proposed type locality is in a canyon known 

informally as “Cathedral Canyon,” so named for the 

spectacular tent rocks developed in the Otowi and La 

Cueva members (Gardner et al. 2010). The type locality 

is the feature labeled “Tent Rocks” on the Jemez Springs 

USGS 7.5-minute topographic map (see “Tent Rocks” 

section). The La Cueva Member is not included in the 

GRI GIS data.

Otowi Member

The Otowi Member erupted during formation of the 

Jemez

Mountains

White 

Rock

Canyon

Pajarito Plateau

WEST EAST

Tschicoma

Formation Puye Formation

fanglomerate

Bandelier Tuff

basalt

Puye Formation axial gravel

Cerros del Rio

volcanic rocks

basalt

Santa Fe Group

Pliocene alluvium

Pajarito

fault zone

Figure 9. Geologic sketch of the Pajarito Plateau. Bandelier National Monument is on the northeastern Pajarito 

Plateau, which exposes deep canyons that separate narrow mesas capped by Bandelier Tuff. Volcanoes that produced 

the Tschicoma Formation shed sediment to form ancient alluvial fans (Puye Formation). Rio Grande rift–filling 

sediments (Santa Fe Group) underlie cobbles, pebbles, and gravels of the Puye Formation. Cerros del Rio volcanic rocks 

erupted on the periphery of the Jemez Mountains volcanic field. Graphic by Trista Thornberry-Ehrlich (Colorado State 

University) after Reneau and McDonald (1996, figure 6 in Introduction) and Waresback and Turbeville (1990, figure 2).
13

Bandelier Tuff

(900 m [2,950 ft])

Bandelier Tuff

(120 m [390 ft])

Otowi

Member

(Qbo)

1.61

million

years ago

(e.g., Qct;

1.38 

million

years ago)

Pyroclastic flows erupted 

during formation

of Valles caldera

densely welded to 

nonwelded ignimbrites

Plinian eruption

of ash fall

Tsankawi Pumice Bed

Cerro Toledo Formation

(about 520 m [1,700 ft])

poorly welded to densely 

welded ignimbrites

Guaje Pumice Bed

Eruption of domes 

in Toledo caldera 

and slope 

movements

Pyroclastic flows erupted

 during formation of Toledo 

 caldera

Bandelier Tuff

(80 m [260 ft])

La Cueva

Member

1.85

million

years ago

Plinian eruption

of ash fall

nonwelded to poorly 

welded ignimbrites

Rhyolite domes, ash fall, debris

flows, and reworked colluvial matieral

Fluvial gravel or

poorly developed

soil

Pyroclastic flows 

erupted during an 

early leak of 

Bandelier magma 

chamber

surge beds

vapor phase notch

Tshirege

Member

(Qbt)

1.25

million

years

ago

Qbt 4u

Qbt 3

Qbt 2

Qbt 1

Qbt 5u

Qbt 5l

Qbt 4l

Qbt 3t

cavates

cavates

tent rocks

deeply worn trails

tent rocks

tent rocks

Figure 10. Stratigraphic column for Bandelier Tuff. Bandelier Tuff is divided into three members: La Cueva, Otowi, and 

Tshirege. Notably, in no one place—neither within nor beyond Valles caldera—can the entire stratigraphic column be 

seen. The two gigantic explosions that deposited the Otowi and Tshirege members were separated by about 400,000 

years, during which time rhyolite domes erupted in Toledo caldera; lava flows, domes, ash, and colluvial material 

from slope movements at that time make up the Cerro Toledo Formation. About 200,000 years separates deposition 

of the La Cueva and Otowi members. The Tshirege Member has no major unconformities between its flow units, 

neither within nor outside Valles caldera. The lack of sediments, debris flows, lacustrine deposits, lava flows, or soils 

suggests that the Tshirege Member was emplaced in a relatively short period of time, possibly less than a week or 

two and certainly less than a few months. Geologists have divided the Tshirege Member (Qbt) into subunits using 

geologic, stratigraphic, chemical, and mineralogical data. The Qbt1 subunit contains cavates, trails, and tent rocks. In 

the Tsankawi Section of Bandelier National Monument, some cavates occur in the underlying Tsankawi Pumice Bed. 

Like the Tshirege Member, the Otowi and La Cuesta members host tent rocks. Graphic by Trista Thornberry-Ehrlich 

(Colorado State University) after Broxton and Reneau (1995, figure 4), Warren et al. (2007, figure 2), information from 

Gardner et al. (2010), Sussman et al. (2011, figure 3), and Goff et al. (2014, figure 3). 
14

Toledo caldera. It has 40Ar/39Ar ages of 1.61 ± 0.01 to 

1.62 ± 0.04 million years ago (Izett and Obradovich 

1994; Spell et al. 1996). The generally poorly welded 

Otowi Member varies greatly in thickness as a result 

of burial of preexisting topography and subsequent 

erosion (Broxton and Reneau 1996). The maximum 

thickness of the Otowi Member is 120 m (390 ft) (Goff 

et al. 2011). The basal unit of the Otowi Member, 

the Guaje Pumice Bed (Qbog), is too thin to have 

been mapped as a separate unit within the national 

monument, but exposures of it crop out in several 

canyons (Fraser Goff, New Mexico Bureau of Geology 

and Mineral Resources, volcanologist, written 

communication, 28 April 2015).

Tshirege Member 

The Tshirege Member forms the orange to pink cliffs 

characteristic of the Pajarito Plateau (fig. 11). It erupted 

in conjunction with the formation of Valles caldera as 

multiple flows of variable thicknesses. It has an 40Ar/39Ar 

age of 1.25 ± 0.01 million years ago (Phillips et al. 2007). 

Like the Otowi Member, the variable thickness of the 

Tshirege Member is associated with burial of preexisting 

topography and subsequent erosion (Broxton and 

Reneau 1996). The maximum thickness of the Tshirege 

Member is 900 m (2,950 ft) (Goff et al. 2014).

Since the 1960s, geologists studying volcanism of 

Valles caldera have identified and divided the Tshirege 

Member into numerous distinct units. Smith and Bailey 

(1966) first defined five (I through V) “cooling units” for 

the entire Jemez Mountains volcanic field. A “cooling 

unit” consists of a single flow or a sequence of flows 

that cooled as a single entity. Later workers defined 

various subunits for the Pajarito Plateau that closely 

corresponded to the original definitions (Broxton and 

Reneau 1995). More recently, Goff et al. (2014) revised 

the stratigraphy of the Tshirege Member to include 

more subunits (fig. 10), reflecting the evolution of the 

Bandelier magma chamber and associated eruptions. 

The cliffs in Frijoles Canyon are composed of

subunit 1 (Qbt1; fig. 10). This subunit was originally 

divided into a lower glassy part (Qbt-1g; g for “glassy”) 

and an upper devitrified (crystalline) part (Qbt-1v; v 

for “vapor phase”) by Vaniman and Wohletz (1990; 

1991). A vapor-phase notch—a thin, horizontal zone of 

preferential weathering—forms an easily recognizable 

horizon throughout much of the Pajarito Plateau. This 

notch, which was first described by Crowe et al. (1978), 

marks the transition from glassy tuffs to the crystallized 

tuffs in subunit Qbt1. The bench of the vapor-phase 

notch marks the base of the “Qbt-1v unit”; in the most 

recent revision of Tshirege Member stratigraphy, the 

“v” and “g” designations of this subunit were dropped 

(Goff et al. 2014). 

The base of the Tshirege Member consists of the 

Tsankawi Pumice Bed, which is found in only a few 

gullies around Valles caldera (Goff 2009). It was not 

mapped as a separate unit in Bandelier National 

Monument (see GRI GIS data). The Tsankawi Pumice 

Bed is less than 2 m (7 ft) thick and consists of a 

pyroclastic surge deposit that is composed of thin, 

stratified layers of pumice (fig. 10; Goff et al. 2011). 

Pyroclastic surge deposits represent turbulent flow as 

an eruption column collapses.

Features in Bandelier Tuff

The soft and easily eroded nature of Bandelier Tuff 

allowed the deep Frijoles Canyon to be incised by El 

Rito de los Frijoles (Frijoles Creek), and then provided 

an ideal setting for a prehistoric Puebloan community 

(Dunbar 2010a). Ancient peoples carved dwellings, 

called “cavates,” into cliffs of the Tshirege Member. 

They also eroded, and in some cases intentionally 

constructed, a trail system in the member. In addition 

Figure 11. Photograph of Tshirege Member of Bandelier 

Tuff. The lower part of subunit Qtb1 (see fig. 10) of 

the Tshirege Member is characterized by the presence 

of abundant volcanic glass, lack of welding, and 

a distinctive Swiss cheese–like appearance. These 

characteristics allowed for the excavation of cavates. 

The tuff shown in the figure is of a cliff face above 

Long House in Frijoles Canyon. National Park Service 

photograph by Ron Kerbo (Geologic Resources Division).
15

to these culturally significant features, distinctive 

tent rocks (hoodoolike features) formed in all three 

members of Bandelier Tuff.

Cavates

Bandelier Tuff and cavates (hollowed-out chambers) go 

hand-in-hand. According to Toll (1995, p. 2), “although 

it is not possible...to draw the absolute limits of cavate 

distribution in northern New Mexico, there is little 

doubt that the line would follow the boundaries of the 

Bandelier Tuff.” 

During the 12th through 16th centuries, ancestral 

Puebloans who lived on the Pajarito Plateau hollowed 

out these chambers in cliff walls. In Bandelier National 

Monument, abundant cavates were excavated in several 

canyons, notably Frijoles. In addition, cavates were 

excavated on the southern and eastern slopes of the 

mesa at the Tsankawi unit of the monument (Toll 1995). 

Today, cavates appear as groups of chambers in the 

lower cliff faces. When they were in use, however, 

most were concealed back rooms of larger cliff-side 

villages constructed of masonry. Most of the masonry 

structures have collapsed (see “Cavate Deterioration” 

section).

By definition, cavates are primarily the result of 

excavation of the Bandelier Tuff by humans (Toll 

1995). Geologic factors such as welding and surface 

weathering, however, influenced where excavation 

occurred. Using tools such as digging sticks and 

sharpened stones, builders pecked, carved, and chiseled 

out nonwelded tuff, cutting progressively deeper into 

the cliff face until a room reached a desired shape and 

size. In locations where cavates were excavated, the 

tuff is commonly “case hardened” by dissolved silica 

that reprecipitated as a thin crust on the canyon wall. 

Breaking through this outer hard layer provided access 

to more easily worked material (Kiver and Harris 1999). 

Most cavates were carved into the lowest part of the 

Tshirege Member (unit Qbt1; fig. 10), which is whiteto-gray nonwelded tuff that weathers to pale orange. 

This portion of the Tshirege Member has a distinct 

“Swiss-cheese” appearance, containing abundant holes 

as much as 1.5 m (5 ft) across (fig. 11). These holes are 

caused by preferential erosion of pumice clasts in the 

unit (Goff 1995), which are commonly 2 to 5 cm (0.8 to 

2 in) across but can be as much as 14 cm (6 in) across 

(Broxton et al. 1995). With the loss of these clasts, large 

holes penetrated case-hardened cliff faces and exposed 

the soft underlying material to further wind and water 

erosion (Broxton et al. 1995). 

Although most of the cavates occur in subunit Qbt1

(fig. 10) of the Tshirege Member, the stratigraphically 

lowest cavates at Tsankawi Section were hollowed out 

of a distinctive reddish layer of the tuff—the Tsankawi 

Pumice Bed of the Tshirege Member (fig. 10). This layer 

contains large chunks of pumice and is much softer than 

the overlying gray tuff at this location. Toll (1995) noted 

that Tsankawi Pumice Bed is thicker at this location 

than elsewhere (as described by Bailey et al. 1969).

Trails

Ancestral people of the Pajarito Plateau developed a 

trail system that originally stretched for hundreds of 

kilometers (Snead 2005). The same soft bedrock that 

allowed ancient inhabitants to carve cavates into sheer 

canyon walls became eroded by the passage of human 

feet (fig. 12). Many of these trails show signs of having 

Figure 12. Photograph of trail in Bandelier Tuff. 

Generations of use have worn a trail into Bandelier 

Tuff at the Tsankawi Section of Bandelier National 

Monument. National Park Service photograph by 

Sally King (Bandelier National Monument), available 

at http://www.nps.gov/band/photosmultimedia/

photogallery.htm (accessed 20 August 2014).
16

been constructed intentionally, for example, with steps 

carved into bedrock by hand (Snead 2005).

The trail system in the Tsankawi Section of the 

monument linked mesa-top homes to fields and springs 

in the canyons below. Deeply worn sections of the trail 

occur in the upper part of subunit Qbt1 (fig. 10). By 

contrast, subunit Qbt2 is relatively resistant to erosion 

and constitutes the main cap rock of the mesas on 

the eastern side of the Pajarito Plateau (Reneau and 

McDonald 1996).

Many petroglyphs—pictures or signs, consisting of 

humanlike figures and geometric forms (fig. 13)—

pecked or chipped into Qbt2 probably served as trail 

markers. Petroglyphs along the trail usually appear on 

rock faces where people climbing up from below could 

easily see them (Snead 2005). Although the symbolic 

repertoire of trail markers is not understood today, a 

reasonable conclusion is that they were indicators of 

territory or local identity that people traveling through 

would have readily recognized (Snead 2005).

Tent Rocks

Conical, teepee-shaped landforms (fig. 14)—locally 

called “tent rocks” by Griggs (1964)—occur in all 

three members of Bandelier Tuff. Notable tent rocks 

in the Otowi Member occur along the rim of Valles 

caldera and in Alamo Canyon. In the Tshirege Member 

(particularly the lower part of subunit Qbt1; fig. 10), 

tent rocks occur in Frijoles Canyon (Griggs 1964; Self 

et al. 1996; Dethier and Kampf 2007; Jacobs and Kelley 

2007). Tent rocks are also common in some tuffs of the 

Valle Toledo Member of the Cerro Toledo Formation 

(Gardner et al. 2010), parts of the Puye Formation, and 

parts of the volcaniclastic sequence interbedded within 

the Paliza Canyon Formation (Fraser Goff, New Mexico 

Bureau of Geology and Mineral Resources, written 

communication, 28 April 2015). 

Scientific literature describing the origin of tent rocks 

at Bandelier National Monument is lacking, though 

Griggs (1964, p. 48) noted that tent rocks are “erosional 

remnants.” Hoard (1989) suggested that some tent rocks 

along the Falls Trail may represent areas where hot ash 

(heated from fumaroles) flowed over small bodies of 

Figure 13. Photograph of petroglyphs at Tsankawi Mesa. Some ancient trails, still used today, are “announced” 

by petroglyphs. The examples shown in the figure are part of the interpretive trail in the Tsankawi Section of the 

monument. They were pecked and chipped into subunit Qbt2 (see fig. 10) of the Tshirege Member of Bandelier Tuff. 

National Park Service photograph by Sally King (Bandelier National Monument).
17

water. The resultant steam caused chemical reactions 

that hardened the ash at these locations, making them 

more likely to be preserved as tent rocks as the softer 

surrounding rock eroded away. Commonly, a large 

boulder or cobble will cap tent rocks. This has led to 

all kinds of speculations about earthquake magnitudes 

and stability of the Pajarito Plateau (Fraser Goff, New 

Mexico Bureau of Geology and Mineral Resources, 

written communication, 28 April 2015).

Tent rocks have similarities to pillarlike, erosional 

“hoodoos” common in some parks on the Colorado 

Plateau such as Bryce Canyon National Park (see 

National Park Service 2014b and the GRI report by 

Thornberry-Ehrlich 2005). The conical shape of tent 

rocks, however, is typically found in volcanic rocks 

whereas hoodoo pillars usually form in sedimentary 

rocks.

Notable examples of tent rocks formed in tuff outside 

of Bandelier National Monument include the Peralta 

Tuff Member in Kasha-Katuwe Tent Rocks National 

Monument, which is southwest of Bandelier National 

Monument and administered by the Bureau of Land 

Management (see Smith 1996; Dunbar 2010b). 

Like Bandelier, Kasha-Katuwe is part of the Jemez 

Mountains volcanic field. The Clarno Formation (tuff 

beds) in John Day Fossil Beds National Monument, 

Oregon (Merriam 1901), also host tent rocks (see 

the GRI report by Graham 2014), as do the Rhyolite 

Canyon Tuff in Chiricahua National Monument, 

Arizona (Enlows 1955; see the GRI report by Graham 

2009), and Racer Canyon Tuff in Washington County, 

Utah (Cook 1960). Perhaps the most spectacular tent 

rocks in the Jemez Mountains are in the Puye Formation 

of Rendija Canyon north of Los Alamos (Fraser 

Goff, New Mexico Bureau of Geology and Mineral 

Resources, written communication, 28 April 2015).

Rio Grande Rift 

Spanning 1,000 km (600 mi), from Chihuahua in 

northern Mexico to Leadville in central Colorado, the 

Rio Grande rift is a major feature of crustal extension 

stretching across New Mexico (fig. 15). The southern 

part of the rift began to pull apart about 36 million years 

ago (Eocene Epoch; fig. 1). In the north, rifting began 

Figure 14. Photograph of tent rocks. Conical, teepee-shaped landforms, locally called “tent rocks” by Griggs (1964), 

occur in all members of the Bandelier Tuff. The tent rocks in this photograph are in the Tshirege Member in 

Frijoles Canyon, adjacent to Tyuonyi. National Park Service photograph, available at https://www.flickr.com/photos/

bandeliernps/4749225916/ (accessed 26 December 2014).
18

about 22 million years ago (Miocene Epoch) (Price 

2010).

Santa Fe Group

As the Rio Grande rift began pulling apart, basins such 

as the Española basin dropped down along normal 

faults (fig. 16) and sediments began filling them. In 

parts of the Española basin, sediments are as much 

as 1,450 m (4,800 ft) thick (Galusha and Blick 1971). 

These rift sediments, referred to as the Santa Fe Group, 

include material deposited by the ancestral Rio Grande. 

Modern alluvium and terrace deposits are not included 

as part of the Santa Fe Group (Spiegel and Baldwin 

1963).

According to Kelley et al. (2013), the two primary 

formations within the Santa Fe Group are the Tesuque 

Formation (19 million–13.5 million years old), which 

Figure 15. Map of the Rio Grande rift. Bandelier National Monument lies on the western edge of the Española basin, 

which is one of nine basins along the Rio Grande rift. These basins have dropped down as Earth’s crust has pulled 

apart in the rift. From north to south, these basins are the San Luis basin (SLB), Española basin (ESB), Albuquerque 

basin (ALB), Socorro basin (SB), Palomas basin (PB), Jornada basin (JB), Tularosa basin (TB), Mesilla basin (MB), and 

Hueco basin (HB). Graphic by Trista Thornberry-Ehrlich (Colorado State University) after Connell et al. (2005). Base map 

by Tom Patterson (National Park Service). 
19

Figure 16 (above). Schematic illustration of a normal 

fault. The Pajarito fault zone, which displaces the 

Bandelier Tuff in Bandelier National Monument, 

consists of normal faults. Faulting occurs along a 

fault plane. Footwalls are below the fault plane 

and hanging walls are above. In a normal fault, 

crustal extension (pulling apart) moves the hanging 

wall down relative to the footwall. A steep cliff or 

topographic step, called a “fault scarp,” separates 

the upthrown and downthrown sides of the fault. 

In the presence of a stream, an alluvial fan may 

form at the base of a fault scarp. Graphic by Trista 

Thornberry-Ehrlich (Colorado State University).

Figure 17 (right). Schematic illustration of surface 

expressions of deformation within normal fault 

zones. The structural geology of Bandelier National 

Monument is dominated by normal faulting within 

the Pajarito fault zone. The figure shows a series 

of schematic sketches, originally drawn by John 

Wesley Powell in 1873, that highlight the contrasting 

styles of deformation that investigators have 

mapped along strike in the Pajarito fault zone. 

Along the strike of a given structure, deep-seated 

normal faulting can be expressed at the surface 

as a spectrum of styles that show a simple normal 

fault with prominent scarp (A), broad zone of small 

normal faults (B), monocline with normal fault at 

depth (C), and faulted monocline (D). This figure 

does not represent actual cross sections at Bandelier 

National Monument. Graphic by Trista ThornberryEhrlich (Colorado State University) after Powell 

(1873) and Gardner et al. (1999, figure 10). 
20

is the principal basin-filling unit in the region, and 

Chamita Formation (13.5 million–7.5 million years old). 

The Tesuque Formation consists of sandstone (Tstc) 

and basalt flows (Tstb). The Chamita Formation (Tscv) is 

sandstone, composed of fluvial sand and gravel (Koning 

et al. 2005). 

Minor amounts of basaltic lava extruded into Santa Fe 

Group sediments from roughly 25 million to 16 million 

years ago (late Oligocene to Miocene; fig. 1), thus 

providing an indication for timing of deposition (Goff 

2009). As mapped by Dethier et al. (2011), some basalt 

flows and cinders (Tsfb) that erupted into the rift occur 

near the southwestern boundary of Bandelier National 

Monument. 

The youngest member of the Santa Fe Group in 

Bandelier National Monument is the axial channel 

facies (QTsfa). This unit represents the main channel of 

the ancestral Rio Grande flowing in the deepest part of 

the valley. The rock unit is interlayered with 2.5-millionyear-old basalt flows from the Cerros del Rio volcanic 

field (Bachman and Mehnert 1978).

Pajarito Fault Zone

The Pajarito fault zone, which runs across Bandelier 

National Monument, delineates the western active 

margin of the Rio Grande rift (see “Seismic Activity” 

section). The zone is composed of numerous unnamed 

and named faults (e.g., Cerro Colorado, Cerro Micho, 

Cerro Portillo, Cochiti Cone, Cochiti, East Buckman, 

Pines Canyon, San Ildefonso, Totavi, Twin Hills, West 

Buckman, and White Rock faults; see GRI GIS data). In 

map view, the main trace of the fault zone is 1.5 to 3 km 

(0.9 to 2 mi) wide and about 50 km (30 mi) long. The 

swath of deformation consists of north–south-oriented 

normal faults (figs. 16 and 17) where rocks have moved 

down to the east, forming a prominent 120-m- (390-ft-) 

high escarpment (Olig et al. 1996). Topographically, the 

fault zone defines the boundary between the mountains 

and mesas (Broxton and Vaniman 2005; Jacobs and 

Kelley 2007). Vertical displacement along the fault zone 

ranges from about 40 m (130 ft) to more than 200 m 

(660 ft) (Olig et al. 1996; Gardner et al. 1999; Goff et al. 

2002a, 2002b). Displacement of the 1.25-million-yearold Tshirege Member in Frijoles Canyon is about 145 

m (480 ft) (Reneau 2000). The amount of displacement 

is highest in the central part of the fault zone and 

decreases north of Los Alamos Canyon where the fault 

zone is primarily exposed as a monocline (one-limbed 

fold in otherwise flat-lying strata; fig. 17) (Olig et al. 

1996). This monocline is delineated as a “fold” in the 

GRI GIS data.

Cerros del Rio Volcanic Field

As a consequence of extension, Earth’s crust has 

thinned within the Rio Grande rift, allowing higher 

heat flow from Earth’s mantle to reach the surface. 

Some volcanism in the monument area occurred in 

Figure 18. Photographs of a Cerros del Rio cinder 

cone. The Tshirege Member of the Bandelier Tuff (Qbt) 

overlies a Cerros del Rio cinder cone (QTcrv and as 

indicated by arrow) near Upper Frijoles Falls in Frijoles 

Canyon. About 3 million years ago, basalt erupted as 

part of the Cerros del Rio volcanic field and built up 

this cone. At 1.25 million years ago, a pyroclastic flow 

composed of Bandelier Tuff emanating from the Valles 

caldera covered the cinder cone. Photographs by Katie 

KellerLynn (Colorado State University).
21

connection with the development of this rift. For 

example, lava erupted from a group of vents at the edge 

of the Española basin. These vents were part of the 

Cerros del Rio volcanic field and are now buried under 

rocks of the Jemez Mountains volcanic field. 

The Cerros del Rio volcanic field was one of three 

peripheral volcanic fields to the Jemez Mountains; the 

other two were El Alto and Santa Ana Mesa. The Caja 

del Rio basalt plateau east of the Rio Grande (river) is a 

major geographic feature associated with the Cerros del 

Rio volcanic field (fig. 6). 

Cerros del Rio volcanic rocks (QTcrv) and other rocks 

of this volcanic field (Tcbm, Tcbc, Tcba, and Tclf) erupted 

between about 2.7 million to 1.0 million years ago. 

Most Cerros del Rio eruptions took place before the 

formations of the Toledo and Valles calderas, though 

some late-stage eruptions post-date the Tshirege 

Member (1.25 million years ago; Thompson et al. 2011). 

Cerros del Rio volcanic rocks are primarily basaltic, 

with silica contents ranging mainly from 48% to 60%, 

but as high as 65% (table 1; Koning and Read 2010). 

Ancestral Puebloans used higher silica volcanic rocks 

such as dacite (63%–68% silica) from this volcanic field 

for tool making (see “Lithic Resources” section).

Peripheral volcanic fields were dominated by cinder 

cones and low shield volcanoes (fig. 5). Frijoles Canyon 

contains the remains of a Cerros del Rio cinder cone 

(fig. 18). The Cerros del Rio volcanic field also is 

marked by maar volcanoes that formed when hot, 

rising magma interacted with a water source, such 

Figure 19. Schematic illustration of a maar explosion. During phreatomagmatic eruptions in the Cerros del Rio volcanic 

field, explosive magma–water interactions formed maar deposits. Graphic by Trista Thornberry-Ehrlich (Colorado State 

Univerisyt) after Heiken et al. (1996, figure W11) and Wohletz and McQueen (1984).
22

as shallow groundwater, a stream, or a lake (fig. 19). 

These eruptions are “phreatomagmatic,” with phreato 

meaning “reservoir” or “well” in Greek. In the case 

of Cerros del Rio maar volcanoes, magma-water 

interactions occurred near the ancestral Rio Grande 

(Aubele 1978; Dethier 1997; Heiken et al. 1996). 

Fittingly, the name “Cerros del Rio” means “Mountains 

of the River” in Spanish. A maar volcano—about 3 

km (2 mi) across and 30 m (100 ft) high at the crater 

rim—is exposed in Frijoles Canyon (fig. 20). Colorful 

layered deposits in the canyon walls are remnants of 

this volcano. Thick Cerros del Rio andesite flows, which 

probably erupted from a vent east of the ancestral river, 

overlie maar deposits at this location. 

After the maar volcano built up above the level of 

the water, or water level dropped, the eruption style 

changed to basaltic lava flows and cinders from 

intermittent lava fountains. Eventually activity ceased, 

and lava in the throat of the volcano hardened in place. 

Today, water cascades over this resistant basalt at Upper 

Frijoles Falls (fig. 21). 

Figure 20. Photograph of maar and lava flow in Frijoles 

Canyon. Colorful, bedded rock layers along the Falls 

Trail are maar deposits overlain by a massive lava flow 

and river gravels. A maar volcano in the Cerros del 

Rio volcanic field created these deposits as magma 

interacted with groundwater and/or surface water 

associated with the ancestral Rio Grande. Photograph 

by Katie KellerLynn (Colorado State University).

Figure 21. Photograph of Upper Frijoles Falls. Water cascades over resistant basalt, which erupted from the Cerros del 

Rio volcanic field. The red-bedded deposits are remnants of a maar volcano, which was also part of the Cerros del Rio 

volcanic field. National Park Service photograph by Hal Pranger (NPS Geologic Resources Division).
23

Above Upper Frijoles Falls, Frijoles Canyon broadens. 

Along the northeastern canyon wall, a paleocanyon 

of the Rio Grande (river) is exposed (fig. 22). 

This paleocanyon is a spectacular example of past 

topography captured in stone and preserved by a 

pyroclastic flow. The Tshirege Member of Bandelier 

Tuff (Qbt) completely filled this earlier canyon, which 

the ancestral river created as it ran through the Cerros 

del Rio volcanic field. Thus 1.25 million years ago, the 

Rio Grande (river) was located as much as 2 km (1.2 mi) 

west of the modern river. Moreover, the canyon was 

much narrower than in modern times, with a maximum 

width of about 600 m (2,000 ft). Also, the canyon was 

apparently unmodified by slope movements, such as 

extensive slumps like those along the modern channel 

(Reneau et al. 1995). 

Lithic Resources

The rocks of the Jemez Mountains yielded a variety 

of lithic resources, as detailed by Head (1999). People 

living on the Pajarito Plateau used three primary 

types to fashion tools for hunting, harvesting, food 

preparation, defense, and rituals; these are obsidian, 

dacite, and chert. Sources for these raw materials occur 

in the vicinity of Bandelier National Monument (fig. 

23). 

Obsidian

Obsidian (fig. 24) is volcanic glass found most 

commonly in lava flows or domes of rhyolitic 

composition. High-quality obsidian is usually jet black 

and free of bubbles, crystals, and imperfections (Goff 

2009). The glassy texture of obsidian is produced by 

the lack of a crystalline structure and gives rise to 

conchoidal (smoothly curved, referring to a conch shell) 

fractures, which are useful for scraping. Conchoidal 

fractures generally produce razor-sharp edges, useful 

for cutting. These properties made obsidian a valued 

resource for making hunting points and cutting tools 

(National Park Service 2014d). Because of its sharp 

cutting edge (sharper than stainless steel), obsidian is 

used in some surgical procedures today (Goff 2009).

Glassy obsidian is abundant in several areas of the 

Jemez Mountains, including Valles caldera (fig. 23). 

Cerro del Medio, on the eastern edge of the caldera, is 

composed of Valles Rhyolite, which contains obsidian. 

Valles Rhyolite accompanied the development of the 

resurgent caldera, building up into domes around the 

perimeter of the uplifted caldera floor (see “Geologic 

History” chapter). Other domes in the caldera, for 

example Cerro del Abrigo and Cerros del los Posos, 

also yield obsidian (Baugh and Nelson 1987), but unlike 

Cerro del Medio, these other two domes are composed 

of rhyolite of the Cerro Toledo Formation, which 

erupted in the Toledo caldera between the eruptions of 

the Otowi and Tshirege members of Bandelier Tuff. 

The Valle Toledo Member of the Cerro Toledo 

Formation (Qct) represents a major source of obsidian, 

with Obsidian Ridge as its best known locality. Deposits 

also occur in the walls of Capulin and Alamo canyons. 

Rabbit Mountain, which is composed of rhyolite 

(Qcrm), has deposits of obsidian. Additionally, blocks 

of obsidian occur in the Old Rabbit Mountain debris 

flow (Qrd1), which is also part of the Cerro Toledo 

Formation. Furthermore, erosion through the millennia 

has transported obsidian into various streams, such 

as El Rito de los Frijoles, where it occurs in alluvial 

sediment and stream cobbles (Allen 2004). 

Dacite

Lithic assemblages within Bandelier National 

Monument are commonly 80% or more dacite (Civitello 

and Gauthier 2013). Cerros del Rio volcanic rocks 

(QTcrv) are the main source of this dacite. Although 

the Cerros del Rio volcanic field is primarily composed 

Figure 22. Photograph of paleocanyon of the Rio 

Grande. High on the eastern wall of Frijoles Canyon, 

Bandelier Tuff fills a large channel of the ancestral 

Rio Grande (dotted line) that had cut into basalt 

as it flowed across the Cerros del Rio volcanic field. 

The modern channel is 2 km (1.2 mi) east of this 

paleochannel. New Mexico Bureau of Geology and 

Mineral Resources photograph.
24

of basalt, some dacite (interpreted as remelted crustal 

material) also occurs (Thompson et al. 2001). This has 

caused some confusion in archeological studies, where 

dacite has mistakenly been identified as basalt (Shackley 

2011). 

Late in the eruption of the Cerros del Rio volcanic field, 

dacite domes and lava flows extruded onto the surface. 

Exposures of dacite occur at the mouths of tributary 

canyons to the Rio Grande (Dethier 1997; Thompson 

et al. 2011), and include a dacite quarry in Bandelier 

National Monument that was utilized by ancestral 

Puebloans. Today, it is a popular field trip stop for 

archeology students (fig. 25). The dacite quarry at the 

monument exploited an aphanitic (fine-grained) variety 

of dacite (table 1). 

Figure 23. Map of lithic resources. The graphic shows the extent of El Cajete pyroclastic beds (Qvec) and its source 

(El Cajete crater). Ancestral Puebloans took advantage of the water-retention capabilities of the pumice material for 

farming. The graphic also shows source areas of obsidian (orange), including Cerro del Medio, Rabbit Mountain, and 

Obsidian Ridge, and source areas of chert. At the mouths of tributaries to the Rio Grande (within yellow area on the 

graphic), Cerros del Rio volcanic rocks (QTcrv) yielded dacite suitable for tool making. Bandelier National Monument 

contains a dacite quarry that exploited this material (see fig. 25). Graphic by Trista Thornberry-Ehrlich (Colorado State 

University) using GRI GIS data set for Bandelier National Monument and information from Baugh and Nelson (1987), 

Kilby and Cunningham (2002), Walsh (2005), Gauthier et al. (2007), and Civitello and Gauthier (2013). Digital elevation 

data from USDA NRCS Geospatial Data Gateway (https://gdg.sc.egov.usda.gov/; accessed 7 May 2015).
25

The Tschicoma Formation also contains dacite. Cerro 

Grande (Ttcg), Pajarito Mountain (Ttpm), and Sawyer 

Dome (Ttsd) are composed of various dacites of the 

Tschicoma Formation. Additionally, reworked gravels 

of late Quaternary stream terraces in Frijoles Canyon 

are composed of 40% dacite (Reneau 2000). Tschicoma 

dacites, however, are porphyritic, having abundant 

coarse-grained crystals, and most are highly porphyritic. 

Also, the dacite in terrace gravels discussed by Reneau 

(2000) is porphyritic. The texture of porphyritic dacite 

would have made it unsuitable for making tools and 

projectile points (Fraser Goff, New Mexico Bureau of 

Geology and Mineral Resources, volcanologist, written 

communication, 28 April 2015). 

Chert

Cerro Pedernal (“Flint Peak”)—a flat-topped mountain 

west of the town of Abiquiu, New Mexico, in the 

northern Jemez Mountains, north of Bandelier National 

Monument (and beyond the GRI GIS data set)—is 

the primary source area of Pedernal chert, which 

occurs within the Miocene Abiquiu Tuff (Smith 1938; 

Church and Hack 1939). This formation consists of 

stream-laid tuff and volcanic conglomerate, with a few 

small interbedded lava flows. Additionally, lenses of 

the formation crop out in San Pedro Parks, about 20 

km (12 mi) to the west/southwest of Cerro Pedernal, 

and are discontinuously exposed between Cerro 

Figure 24. Photograph of obsidian. Obsidian (volcanic 

glass) has properties that make it a valuable source for 

tool making. Conchoidal (smoothly curved) fracturing 

produces edges useful for scraping. Also, obsidian can 

be “flaked” into pieces with razor-sharp edges useful 

for cutting. Photograph by Elaine Jacobs (Los Alamos 

National Laboratory).

Figure 25. Photograph of dacite quarry. Students participating in an archeological field trip visit the dacite quarry in 

Bandelier National Monument. Photograph by M. Steven Shackley (taken in 2006, used by permission).
26

Pedernal and San Pedro Parks (Kilby and Cunningham 

2002). Pedernal chert occurs closer to Bandelier 

National Monument as cobbles along the Rio Grande 

(river), perhaps explaining its abundance in the lithic 

assemblages at many local archeological sites (Acklen 

1993).

Pedernal chert is typically translucent and varies in 

color from white to gray with dendritic and amorphous 

discolorations ranging from black to red, blue, and 

yellow. The colors vary widely across small areas of 

the material and may all be visible within a single small 

specimen. Pedernal chert is of high quality for flaking 

(creating flakes of material for tool production), but 

useful pieces are occasionally limited in size due to 

“vugs” (cavities) and internal fractures (Kilby and 

Cunningham 2002).

El Cajete Pyroclastic Beds

After the collapse of Valles caldera, a series of rhyolitic 

domes erupted within the bowl-shaped depression 

(see “Geologic History” chapter). El Cajete crater in 

the southern part of the caldera (see figs. 23 and 38) 

marks one of the vents that erupted at that time. The El 

Cajete pyroclastic beds (Qvec) were ejected from this 

vent. During the eruption, the wind blew mostly to the 

south and east, transporting pumice throughout the 

southeastern Jemez Mountains. Now, the pumice-rich 

El Cajete pyroclastic beds serve as a time-stratigraphic 

marker east, southeast, and south of Valles caldera 

(Reneau et al. 1996). The El Cajete eruption has been 

dated at about 60,000–50,000 years ago (Toyada et al. 

1995; Reneau et al. 1996). This “marker bed” helps to 

date rocks and deposits with respect to their relative 

position to this distinctive layer.

Beginning in the 1200s, ancestral Puebloan populations 

began to settle and farm areas of El Cajete pyroclastic 

beds. Even the smallest pumice fields—less than 1 ha 

(2 ac)—commonly had an ancestral Puebloan “field 

house” structure associated with them. Surveys within 

Bandelier National Monument were the first to note 

the relationship between field houses and pumice soils 

(Powers and Orcutt 1999; Gauthier and Herhahn 2005).

The pumice clasts in pumice-derived soils are as 

much as 15 cm (6 in) across. Given the relatively high 

proportion of these coarse clasts, at first glance pumicederived soils would seem a poor medium for storing 

water, which is an essential factor in the success of “dry 

farming” that relied on precipitation falling directly on 

the fields. Because pumice is composed of thousands 

of small, interconnecting cavities, however, its capacity 

to store water is great. Instead of only storing water 

between soil particles, pumice stores water within clasts 

(Gauthier et al. 2007). 

A second benefit of soils containing pumice is their 

ability to insulate as surface mulch (fig. 26). Elsewhere 

in the northern Rio Grande region Puebloan farmers 

mulched their fields with gravel and cobbles, which 

they excavated and then spread over the ground 

surface (Lightfoot and Eddy 1995; White et al. 1998). 

Figure 26. Photograph of 

El Cajete pyroclastic beds. 

The presence of El Cajete 

pumice aided in ancient 

agriculture. Pumice, which is 

essentially rhyolitic froth, has 

the capacity to store water. 

Also, larger clasts serve as 

mulch. National Park Service 

photograph, available at 

http://www.nps.gov/band/

historyculture/artfarm.htm

(accessed 21 August 2014).
27

By planting in soils with a surface layer of pumice, 

Bandelier farmers more than likely would have realized 

the same benefits of conserving soil moisture and 

moderating soil temperature without any of the labor 

required for mulching of other soils (Gauthier et al. 

2007).

Paleontological Resources

Published reports of fossils at Bandelier National 

Monument document a packrat (Neotoma spp.) 

midden; and charcoal, wood, and cones of Douglasfir (Pseudotsuga menziesii) from Holocene deposits in 

Frijoles Canyon. Spaulding (1992) reported on this 

midden, which occurs at an elevation of 1,933 m (6,342 

ft) near where El Rito de los Frijoles enters the Rio 

Grande. This midden dates to 3,195 ± 85 radiocarbon 

years before present (Spaulding 1992), which is 2,878–

3,112 calendar years before present, as converted using 

Stuiver et al. (2015). 

Packrat middens are important tools for reconstructing 

the paleoecology and paleoclimate of the last 126,000 

years (late Pleistocene and Holocene epochs; fig. 1) 

in western North America (Tweet et al. 2012). Thirtythree National Park System units, including Bandelier 

National Monument, are known to contain packrat 

middens (Tweet et al. 2012). Packrat middens are 

primarily examined for plant macrofossils, but also 

pollen (Anderson and Van Devender 1995), insects 

(Elias et al. 1992), vertebrates (Mead and Phillips 

1981), stomatal density/carbon isotopes in leaves 

(Van de Water et al. 1994), and fecal pellets (Smith 

et al. 1995; Smith and Betancourt 1998); the dung of 

extinct mammals contained in packrat middens yields 

paleobotanical information (Davis et al. 1984; Mead et 

al. 1986; Mead and Agenbroad 1992; Hunt et al. 2012). 

In addition, charcoal occurs in Holocene terraces, 

rockfall deposits, and alluvium at the monument. Such 

material can be used to interpret landscape evolution, 

including changes in drainages under different climate 

regimes (Reneau 2000). Reneau (2000) dated 16 

charcoal samples from Frijoles Canyon, with ages 

spanning the past 8,000 years.

Humans were present on the Pajarito Plateau by at least 

10,000 years ago (Goff et al. 2002b), and some artifacts 

made from fossils such as petrified wood or fossiliferous 

chert have been found at Bandelier National Monument 

(Tweet et al. 2009). Kenworthy and Santucci (2006) 

presented an overview of fossils found in cultural 

resource contexts in the National Park System. 

With respect to units older than the Holocene Epoch 

(see Map Unit Properties Table, in pocket), the Galisteo 

Formation (Tgs), Santa Fe Group (Tstb, Tstc, Tscv, Tsf, 

and QTsfa), and unconsolidated Quaternary deposits 

(Qp2, 3, 4; Qa2, 3, 4; Qt; Qpa, Qa5; and Qfa) are the 

most likely to contain fossils. Also, fossils may be found 

in ash deposits of the Bandelier Tuff (Qbo and Qbt) 

(Tweet et al. 2009). No fossils at Bandelier National 

Monument have been reported from these units to 

date, but fossils from these units are known elsewhere. 

Future field investigations within the monument may 

recover fossils from one of more of these units (Tweet et 

al. 2009).

High-Elevation Features

At high elevations, prevailing temperatures are so 

low that the ground remains frozen for much, or 

all, of the year. In such environments, the effects of 

repeated freezing and thawing and the growth of ice 

masses in the ground are so pervasive to give rise to a 

characteristic range of landforms. The highest elevations 

at Bandelier National Monument occur on the slopes 

of Cerro Grande; the summit is 3,109 m (10,199 ft) 

above sea level. Boulder fields, rock glaciers, patterned 

ground, and felsenmeer are landforms that occur at 

high elevations in the monument. 

Boulder Fields and Rock Glaciers

Goff et al. (2011) mapped boulder fields (Qrx) at high 

elevations at the rim of Valles caldera, including Cerro 

Grande and Sawyer Dome in Bandelier National 

Monument. Boulder fields consist of boulders as much 

as 3 m (10 ft) in diameter derived from the underlying 

rock unit. They are generally devoid of vegetation. Their 

thicknesses are unknown. Goff et al. (2011) estimated 

the age of these features as Pleistocene and Holocene 

(fig. 1), though the lower limit of Pleistocene timing is 

uncertain. As a consequence, the connection to ice-age 

(Pleistocene) conditions is unclear.

Many boulder fields appear to be rock glaciers (Goff 

et al. 2011), which move in large part through the 

deformation of interstitial ice or ice cores (Blagbrough 

1994). Rock glaciers exhibit flow features such as 

transverse arcuate ridges (Blagbrough 1994). The 

Holocene age of these boulder fields suggests that rock 

glaciers may still be active. 
28

Patterned Ground and Felsenmeer

Patterned ground, consisting of asymmetrical circles, 

polygons, or stripes of rock, and felsenmeer (German 

for “sea of rocks”) are high-elevation features at 

Bandelier National Monument (fig. 27), for example, 

above tree line on Cerro Grande (National Park Service 

2005). Unlike rock glaciers, which move as a result of 

the ice they contain, patterned ground and felsenmeer 

develop from frost heaving (subsurface freezing of 

water and the growth of ice masses that lift up soils, 

rocks, and vegetation). 

Patterned ground and felsenmeer have not been 

thoroughly studied or mapped at Bandelier National 

Monument and their ages are unknown. However, the 

observed abundance of felsenmeer at high elevations 

in the Jemez Mountains may reflect near-glacial 

conditions during the most recent ice age, known as the 

Wisconsinan glaciation (Tierney and Potter 1985; Allen 

2004), which took place approximately 85,000 to 11,000 

years ago.

Galisteo Formation

Although volcanism dominates the geologic story at 

Bandelier National Monument, the oldest rocks in the 

monument were deposited by rivers. Between 56 million 

and 34 million years ago, sediments of the Galisteo 

Formation (Tgs) were deposited in a broad, deep, 

inland basin (Stearns 1943). The Galisteo Formation, 

which is primarily sandstone but also siltstone and 

conglomerate. It predates the Jemez Mountains volcanic 

field by at least 20 million years. Stratigraphically, the 

formation unconformably underlies the Santa Fe Group, 

indicating that a significant period of time passed 

between final deposition of the Galisteo Formation and 

initial development of the Rio Grande rift. The Galisteo 

Formation has been brought to the surface along a fault 

near the southwestern boundary of the monument (see 

poster, in pocket). Cannon (1997) noted an exposure of 

brick red Galisteo sandstone and siltstone in the west 

wall of Capulin Canyon.

Figure 27. Photograph of felsenmeer. Large, angular blocks of rocks in an accumulation known as felsenmeer, meaning 

“sea of rocks” in German, are conspicuous displays of frost action on Cerro Grande. National Park Service photograph 

by Sally King (Bandelier National Monument, taken September 2011).
29

Geologic Resource Management Issues

This chapter describes geologic features, processes, or human activities that may require management 

for visitor safety, protection of infrastructure, and preservation of natural and cultural resources in 

Bandelier National Monument. The NPS Geologic Resources Division provides technical and policy 

assistance for these issues.

During the 2005 scoping meeting (see National Park 

Service 2005) and 2014 conference call, participants 

(see Appendix A) identified the following geologic 

resource management issues:

● Fires, Fluvial Geomorphology, and Slope 

Movements

● Cliff Retreat and Rockfall

● Seismic Activity

● Cavate Deterioration

● Volcano Hazards

● Cochiti Dam and Reservoir

● Disturbed Land Restoration

● Paleontological Resource Inventory, Monitoring, 

and Protection

Resource managers may find Geological Monitoring

(Young and Norby 2009) useful for addressing 

these geologic resource management issues. The 

manual provides guidance for monitoring vital 

signs—measurable parameters of the overall 

condition of natural resources. Each chapter covers 

a different geologic resource and includes detailed 

recommendations for resource managers and 

suggested methods of monitoring. An online version of 

Geological Monitoring is available at http://go.nps.gov/

geomonitoring (accessed 13 August 2015).

As this report was in final review, the foundation 

document was completed for Bandelier National 

Monument (National Park Service 2015). The 

foundation document lists the following as fundamental 

resources or values:

● Archeological resources (including cavates)

● Continuing cultural connections

● Science and research

● Natural landscape

● Wilderness

● Museum collection and archives

Other important resources in the monument as 

identified in the foundation document are recreational 

values/visitor experiences, New Deal era legacy/Civilian 

Conservation Corps Historic Landmark District, 

and other cultural resources. Geologic features and 

processes and some of the resource management 

issues described in this chapter affect those values and 

resources. 

Fires, Fluvial Geomorphology, and Slope 

Movements

Fire has tremendous effects on the landscape of 

Bandelier National Monument (fig. 28; National Park 

Service 2014a). Over the last 40 years, the most notable 

fires affecting the monument were La Mesa Fire in 

June 1977, which burned 6,180 ha (15,270 ac) in and 

near Frijoles Canyon and adjacent Santa Fe National 

Forest; Dome Fire in April 1996, which burned 6,690 

ha (16,520 ac) in and near Capulin Canyon and the 

surrounding Dome Wilderness Area; Cerro Grande Fire 

in May 2000, which started in upper Frijoles Canyon 

and burned approximately 19,020 ha (47,000 ac) in 

the Santa Fe National Forest and Los Alamos National 

Laboratory; and Las Conchas Fire in June 2011, which 

burned more than 63,100 ha (156,000 ac), impacting 

all major watersheds in the monument including more 

than 75% of Frijoles Canyon. Burn severities were high 

on 6,600 ha (16,300 ac) or 35% of the total burned area 

in the monument. The Las Conchas Fire is the largest 

wildfire in New Mexico’s history, to date (National Park 

Service 2014c).

Fire is a driving component in an interconnected 

system that includes streamflow, sediment transport, 

stream channel morphology, and slope movements. 

In general after each of these fires, peak storm-water 

flows increased, erosion and corresponding sediment 

transport increased, channel morphology changed, 

and debris flows occurred (Cannon and Reneau 2000; 

Veenhuis and Bowman 2002; Monroe 2012; Jacobs et 

al. 2014). All of these responses are considered threats 

to archeological resources in the monument, which are 
30

Figure 28. Map of fire extents at Bandelier National Monument. Over the last 40 years, major fires have impacted 

Bandelier National Monument: La Mesa Fire in 1977, Dome Fire in 1996, Cerro Grande Fire in 2000, and Las Conchas 

Fire in 2011. After each fire, peak storm-water flows increased, erosion and corresponding sediment transport 

increased, debris flows occurred, and channel geometry changed in the canyons of the monument. Graphic by Trista 

Thornberry-Ehrlich (Colorado State University) after Veenhuis and Bowman (2002, figure 1) and Monroe (2012, poster 

figure). Digital elevation data from USDA NRCS Geospatial Data Gateway (https://gdg.sc.egov.usda.gov/; accessed 7 

May 2015).
31

fundamental resources as defined by the foundation 

document (National Park Service 2015). As climate 

continues to change, fire, precipitation, and streamflow 

patterns will also change. The development of a climate 

change vulnerability assessment and scenario plan is a 

high priority for the monument (National Park Service 

2015).

Streamflow

Storm–water flow magnitude increases dramatically 

after a wildfire, varying in response to fire severity, soil 

characteristics, and weather patterns. The maximum 

recorded peak flow in Frijoles Canyon before the 1977 

La Mesa Fire was 0.5 m3/s (19 ft3/s). Following this fire, 

maximum peak flows in Frijoles Canyon were 86 m3/s 

(3,030 ft3/s) in July 1978 (Veenhuis 2002). After the 2011 

Las Conchas Fire, maximum peak flows were 269 m3/s 

(9,500 ft3/s) in September 2013 (US Geological Survey 

2014a). During the first year after the La Mesa Fire, 

annual peak flow was 160 times greater than before 

the fire. As vegetation reestablished, annual maximum 

peak flows decreased each year. In the 22 years between 

1977 (the year of the La Mesa Fire) and 1999, however, 

flood magnitudes had not completely returned to prefire magnitudes (Veenhuis 2002). By comparison, two 

months after the Las Conchas Fire, a flood occurred 

in Frijoles Canyon that was 368 times greater than the 

largest recorded peak flow prior to 1977. More than two 

years later (September 2013), the largest flood on record 

occurred (Stephen Monroe, National Park Service, 

Southern Colorado Plateau Network, hydrologist, 

written communication, 28 May 2015).

Additionally, the frequency of large storm-water flows 

increases in response to wildfire (Veenhuis 2002). 

For example, after the 1977 La Mesa Fire in Frijoles 

Canyon, the number of peak storm-water flows greater 

than the pre-fire maximum flow of 0.5 m3

/s (19 ft3/s) 

was 15 in 1977, nine in 1978, and five in 1979 (Veenhuis 

2002). The number of peak flows per year in Frijoles 

Canyon was low from the early 1980s through 2010. 

During the four years since the 2011 Las Conchas Fire, 

more than 10 storm-water flows have occurred each 

year (Stephen Monroe, National Park Service, Southern 

Colorado Plateau Network, hydrologist, written 

communication, 28 May 2015).

Sediment Transport

The amount of suspended sediment (and bed load; 

see “Stream Channel Geometry” section) in a stream 

increases after a fire (fig. 29). After the 1977 La Mesa 

Fire, suspended-sediment concentrations showed 

similar patterns to streamflow; that is, a substantial 

increase in sediment transport the first year after the fire 

with a gradual decrease for about three years thereafter. 

Figure 29. “Before” and “after” photographs of El Rito 

de Los Frijoles. Increased sediment load is an outcome 

of fire, as shown here in Frijoles Canyon. The top 

photograph shows the El Rito de Los Frijoles channel 

“before” the 2011 Las Conchas Fire. The bottom 

photograph shows “after.” National Park Service 

photographs. Top photograph by Dale Coker (Bandelier 

National Monument). Bottom photograph available at 

http://www.nps.gov/band/flashflood.htm (accessed 17 

September 2014).
32

For the first year after the La Mesa Fire, the annual 

sediment load calculated from regression equations 

compared to streamflow was 220 times the annual load 

for the post-recovery period (Veenhuis 2002). For the 

first four years following the Las Conchas Fire, large 

volumes of sediment were transported through all of 

the major drainages at Bandelier National Monument. 

The National Park Service elected not to re-vegetate or 

apply other hillslope stabilization treatments to burned 

areas in Bandelier National Monument and regional 

drought conditions leading up to the fire continued in 

subsequent years, slowing re-establishment of slope 

stabilizing vegetation.

Stream Channel Morphology

After a fire, a stream channel commonly responds to 

the increased magnitude and frequency of streamflow 

and the resultant increase in suspended-sediment 

loads by downcutting and widening. Notably, incision 

may not occur uniformly along the length of a stream 

channel. Areas of incision are strongly influenced by 

lithology. Where exposed in the stream bed, resistant 

lavas impeded incision in Capulin Canyon following the 

1996 Dome Fire (Reneau et al. 1999). Incision also may 

occur beyond a stream channel proper. For example, 

as a result of flooding events that followed the Las 

Conchas Fire—one in July 2013 and two in September 

2013 when 19.1 cm (7.52 in) of rain fell in a five day 

period—notable incision occurred elsewhere (fig. 

30). Significant slope and channel erosion took place 

in Capulin, Alamo, and Frijoles Canyons during each 

of the four years after the Las Conchas Fire (Stephen 

Monroe, National Park Service, Southern Colorado 

Plateau Network, hydrologist, written communication, 

28 May 2015).

Prior to the 1996 Dome Fire, the stream channel in 

Capulin Canyon had a continuous gravel mantle. 

Post-fire floods excavated large volumes of gravel from 

the stream bed and locally exposed erodible bedrock 

(sandstone and nonwelded tuff) beneath the stream 

bed, triggering rapid incision. As much as 2 m (7 ft) of 

incision into bedrock took place in 1996 (Reneau et al. 

1999). A similar dynamic downcutting also took place 

following the Las Conchas Fire in Frijoles Canyon (fig. 

31; Stephen Monroe, National Park Service, Southern 

Colorado Plateau Network, hydrologist, written 

communication, 28 May 2015). 

Prior to the 2011 Las Conchas Fire, stream channel 

substrates in both Capulin Creek and Rito de los 

Frijoles were dominated by cobbles and coarse gravel 

(Stumpf and Monroe 2012). Extensive post-fire, 

watershed-scale erosion mobilized large volumes of 

fine sediments into stream channels. In 2012 substrates 

in the Capulin and Frijoles channels were primarily 

sand and gravel, 88% and 90%, respectively (Stumpf 

and Monroe 2014). These conditions persisted in 2014 

(Stumpf in progress).

Following the 1996 Dome Fire, channel aggradation 

was generally associated with obstructions such as log 

jams or stands of trees along the channel. Some areas 

that had aggraded during the first flood after the Dome 

Fire subsequently were incised by later flood waters. 

Erosion initiated in Capulin Canyon following the 

Figure 30. Photograph of post-fire incision. In 

September 2013 during an epic precipitation and 

flooding episode when 19.1 cm (7.52 in) of rain fell in 

five days, slopes were incised and new channels were 

created. This photograph shows incision on a bench on 

the northeastern flank of Boundary Peak. Boundary 

Peak is on the western boundary of Bandelier National 

Monument. National Park Service photograph by Luke 

Gommermann (Bandelier National Monument). 
33

Dome Fire was reactivated by floods after the 2011 Las 

Conchas Fire (Stumpf and Monroe 2014). The primary 

effect of repeated flooding was excavation and transport 

of previously stored channel sediment (Reneau et al. 

1999).

At the site of maximum incision following the Dome 

Fire in Capulin Canyon, the elevation of the channel 

apparently stabilized within one year, and subsequent 

channel evolution was dominated by lateral erosion 

(Reneau et al. 1999). As a result of vegetation recovery 

in the second year following the fire, magnitude and 

frequency of peak flows decreased, and the stream 

channel began to readjust. The channel at the most 

downstream crest-stage gage, which has the shallowest 

initial valley slope, showed the first signs of aggradation 

(Veenhuis 2002).

Floods and Debris Flows

Rainfall following a fire can trigger floods and debris 

flows. Although both floods and debris flows can be 

destructive, debris flows can occur with little warning, 

are capable of transporting large material over relatively 

gentle slopes, and develop momentum and impact 

forces that can cause considerable destruction. As a 

result, mitigation of debris-flow hazards can be more 

difficult than mitigation of flood hazards (Cannon 

2001). 

Since the 2011 Las Conchas Fire, many large debris 

flows have occurred in Frijoles Canyon (Stephen 

Monroe, National Park Service, Southern Colorado 

Plateau Network, hydrologist, written communication, 

30 March 2015). These have not been studied 

extensively, but repeat light detection and ranging 

(LiDAR) imagery was acquired for the Frijoles Canyon 

Figure 31. Photographs of effects of fire in Frijoles Canyon. At Bandelier National Monument, fire is a driving 

component in an interconnected system that includes streamflow, stream channel geometry, sediment transport, and 

slope movements. Following the 2011 Las Conchas Fire, some areas of Frijoles Canyon were severely incised while 

others significantly aggraded. This photo pair shows an area below the Narrows in Frijoles Canyon where bedrock 

was exposed in the stream channel following the flood event of 26 July 2013 (left). Three months later (October 2013; 

right), the channel is sediment laden. Photographs by Elaine Jacobs (left; Los Alamos National Laboratory) and Anne 

Tillery (right; US Geological Survey).
34

watershed in May 2010 and again in September 2013. 

This sequence captured landscape-scale changes that 

occurred as a result of the Las Conchas Fire (Jacobs et 

al. 2014). Tillery et al. (2011) provided a preliminary 

hazard assessment of debris-flow potential from 321 

basins burned by the 2011 fire. Models incorporating 

burn severity, topography, soils, and storm rainfall 

predicted Frijoles, Alamo, and Capulin canyons to 

have a greater than 80% probability of debris-flow 

occurrence.

Cannon and Reneau (2000) found that the factors 

that best distinguished between debris flow–

producing drainages and flood-producing drainages 

in Capulin Canyon were lithology (rock type 

and physical characteristics) and drainage-basin 

morphology, including area, height, average gradient, 

and ruggedness (basin height divided by the square 

root of the basin area; Melton 1965). Cannon and 

Reneau (2000) compared the response of Capulin 

Creek (i.e., Capulin Canyon basin) and its two 

tributaries—“North Tributary,” locally known as 

Red Canyon, and “South Tributary,” locally known 

as Yellow Canyon (fig. 32). In North Tributary basin, 

a rugged drainage basin morphology, an average 

12% channel gradient, and steep, rough hillslopes 

coupled with colluvium and soil weathered from 

volcaniclastic and volcanic rocks (Paliza Canyon 

Formation, Tppa; and Cochiti Formation, QTc, as 

indicated on the GRI GIS data) promoted erosion 

and the generation of at least one debris flow. 

In the Capulin Canyon basin, less rugged basin 

morphology, an average gradient of 5%, and long, 

smooth slopes mantled with pumice (El Cajete 

pyroclastic beds, Qvec) resulted in flooding. 

The South Tributary basin exhibited negligible 

surface runoff, which Cannon and Rveneau (2000) 

attributed to the limited extent and severity of the 

Dome Fire in this basin. 

Falls Trail after Las Conchas Fire

Following the 2011 Las Conchas Fire, Pranger 

(2012) provided an evaluation of geologic hazards 

at the Lower Frijoles Falls section of the Falls Trail 

in Frijoles Canyon. Post–fire storm water and 

coarse debris had scoured the bedrock slope in the 

canyon, causing collapse, including an entire section 

of the trail, which failed into the stream channel 

(fig. 33). Another section was left precariously 

perched above a 10-m- (30-ft-) high vertical bedrock 

slope. This section ultimately failed in September 

2013 (Hal Pranger, NPS Geologic Resources Division, 

Geologic Features and Systems Branch chief, written 

communication, 24 October 2014). 

As a result of fire-related impacts, the Falls Trail had 

to be closed, creating significant access issues for both 

administrative and public use (Pranger 2012). The trail 

below Upper Frijoles Falls to the Rio Grande remained 

closed as of August 2015 (http://www.nps.gov/band/

planyourvisit/falls-trail.htm; accessed 11 August 2015). 

Figure 32. Map of Capulin Canyon watershed. After the 1996 

Dome Fire, investigators studied Capulin Canyon in order to 

identify hillslope, channel, and fire characteristics as indicators 

of susceptibility for wildfire–related debris flows. The pink 

lines on the map delineate the Capulin Creek, North Tributary 

(Red Canyon), and South Tributary (Yellow Canyon) drainage 

basins. Yellow shading indicates the extent of the Dome Fire. 

Orange shading indicates areas of high and moderate burn 

intensities. Graphic by Trista Thornberry-Ehrlich (Colorado 

State University) after Cannon and Reneau (2000, figure 

1). Digital elevation data from USDA NRCS Geospatial Data 

Gateway (https://gdg.sc.egov.usda.gov/; accessed 7 May 2015).
35

High-resolution LiDAR data sets completed in 2010, 

2013, and 2014, provide a possible means to track 

changes along Falls Trail over a short time span. These 

data could be used to aid trail design if monument 

managers choose to reroute the affected segments of 

the Falls Trail. Such a decision would weigh the expense 

of trail design, construction, and increased visitor risk 

against the benefit of connectivity to the Rio Grande 

(river) (Bilderback 2014). LiDAR analysis could be 

the subject of a future technical assistance request; 

monument managers are encouraged to contact the 

NPS Geologic Resources Division.

Recovery and Monitoring

Watershed recovery is a complex function of fire 

severity, soil conditions, weather patterns, and 

treatment, and can range in time from a few years to 

20 years or longer (Livingston et. al. 2005). Work by 

Cannon (1997, 2001), Reneau et al. (1999), Cannon 

and Reneau (2000), Veenhuis (2002), and Veenhuis and 

Bowman (2002) following the La Mesa and Dome fires 

identified watershed recovery periods of approximately 

four years. Due to the severity of the Las Conchas Fire 

and ongoing drought, Frijoles watershed conditions are 

recovering more slowly than they did following the 1977 

La Mesa Fire (Stephen Monroe, National Park Service, 

Southern Colorado Plateau Network, hydrologist, 

written communication, 28 May 2015). 

After the record-breaking Las Conchas Fire, Bandelier 

National Monument staff began documenting recovery 

in the burned areas by establishing photo points (see 

http://www.nps.gov/band/firerecover.htm; accessed 19 

September 2014). Photographs taken at these points 

will illustrate recovery over time and are a valuable 

tool for park planning (fig. 34). Due to the extreme 

watershed degradation caused by the fire, much of the 

watershed has yet to establish much vegetative cover, 

leaving it vulnerable to large flash floods, even more 

than four years after the initial disturbance event (Kay 

Beeley, Bandelier National Monument, cartographic 

technician, written communication, 10 April 2015).

In the Geological Monitoring chapter about fluvial 

geomorphology, Lord et al. (2009) described methods 

for inventorying and monitoring the following six 

vital signs of stream systems: (1) watershed landscape 

(vegetation, land use, surficial geology, slopes, and 

hydrology), (2) hydrology (frequency, magnitude, and 

duration of streamflow rates), (3) sediment transport 

Figure 33. Photographs of Falls Trail in Lower Frijoles 

Canyon. Falls Trail was built by the Civilian Conservation 

Corps in the 1930s. Workers excavated the trail into 

the side of a cliff face near Lower Frijoles Falls. As an 

outcome of the 2011 Las Conchas Fire, the severely 

damaged trail had to be closed between Upper Frijoles 

Falls and the Rio Grande (river) due to undercutting 

and collapse of the canyon wall. National Park Service 

photographs.
36

(rates, modes, sources, and types of sediment), 

(4) channel cross section, (5) channel planform, and 

(6) channel longitudinal profile. In the Geological 

Monitoring chapter about slope movements, Wieczorek 

and Snyder (2009) described five vital signs for 

understanding and monitoring slope movements: 

(1) types of landslide, (2) landslide causes and triggers, 

(3) geologic materials in landslides, (4) measurement 

of landslide movement, and (5) assessment of landslide 

hazards and risks. This information may be of interest 

and use for monitoring stream channels and slope 

movement in burned areas at Bandelier National 

Monument.

Cliff Retreat and Rockfall

The Tshirege Member of Bandelier Tuff (Qbt) 

dominates the landscape at Bandelier National 

Monument. A combination of welded and nonwelded 

units in the member promotes differential weathering: 

nonwelded units typically erode into broad, gentle 

slopes, whereas slightly to moderately welded units 

tend to form vertical cliffs. Rubble from rockfalls, 

called talus or colluvium (Qc), commonly obscures less 

welded sections, creating a dramatic contrast between 

vertical cliffs of welded units and talus-covered slopes 

of nonwelded units (Ross and Smith 1961). In addition, 

where exposed at the base of Tshirege cliffs in Frijoles 

Canyon, the poorly consolidated deposits of the Cerro 

Toledo Formation (Qct) facilitate cliff retreat, which 

negatively impacts archeological sites including cavates 

(Jacobs and Kelley 2007; National Park Service 2015). 

Figure 34. Photographs of landscape recovery. As vegetation reestablishes following the Las Conchas Fire, annual 

maximum peak flow and suspended sediment transport concentrations will decrease. Top photo pair: Upper 

Frijoles Canyon from Sawyer Mesa Road. Bottom photo pair: Headwaters of Capulin Canyon. National Park Service 

photographs, available at http://www.nps.gov/band/firerecover.htm (accessed 21 January 2015). 
37

BEDROCK UNCONSOLIDATED MATERIALS

(including rock fragments, sheared bedrock, weathered regolith, soils)

NO BEDROCK

FLOW EQUIVALENT

EXISTS

FALLS TOPPLES SLIDES LATERAL SPREADS FLOWS

Translational Rotational

Water

content Wet Dry

Rockfall Soil fall

Debris topple

Rockslide Debris slide

Slump

Rock block slide

Rockfall avalanche Sand flow Loess flow

MAINLY LARGE

ROCK FRAGMENTS

NON-PLASTIC

SORTED SAND OR SILT

MIXED ROCKS

AND SOIL MOSTLY PLASTIC

Rapid earthflow

Sand or silt flow

Debris flow

Debris avalanche

Slow 

earthflow

Extremely 

rapid

Very 

rapid Rapid Moderate Slow Very 

slow

Extremely 

slow

3 m (10 ft)

per second

0.3 m (1 ft)

per minute

1.5 m (5 ft)

per day

1.5 m (5 ft)

per month

1.5 m (5 ft)

per year

0.3 m (1 ft)

per 5 years

Extremely 

rapid

Joint opened (e.g., by 

hydrostatic pressure,

frost or root 

wedging

Removal of support

(e.g., by river erosion,

quarrying, wave action)

B B A

C D E

Ruptured

surface

Extremely slow

to moderate

Undercut by

river

Very 

rapid

Mixed 

sediments

Clayey gravel

Clean sand

Slump

Earth flow

Loess

Glacial clay

Slow

Planar

Failure

along faults

Moderate

Dip slope controlled by 

Scarp face bedding planes

controlled 

by joints

Very slow to

extremely rapid

Very slow 

to rapid

Bedrock

Firm clay

Soft clay with

water-bearing silt

Firm clayey gravel

General lateral

movement of 

soft clays Very 

rapid

Sand

Rapid to

Very rapid

Very 

rapid

Extremely 

rapid

Dry 

sand Firm 

silt

Sand

Rapid to

Very rapid

Extremely 

rapid

Loess

Shale

Weathered

shale

Very 

rapid

Very rapid to

extremely rapid

Bedrock

Regolith

APPROXIMATE RATE OF MOVEMENT

Figure 35. Schematic illustrations of slope movements. Different categories of slope movement are defined by material 

type, nature of the movement, rate of movement, and moisture content. The most common type of slope movement 

in Bandelier National Monument is rockfall from cliffs, though landslides and debris flows have also occurred. Graphic 

by Trista Thornberry-Ehrlich (Colorado State University) after Varnes (1978, figure 4.33 and information therein).
38

Cliff retreat at Bandelier National Monument occurs by 

a combination of small rockfalls from cliffs; detachment 

of rocks from slopes; and larger, deep-seated landslides 

(fig. 35). Small rockfalls from cliffs are the most 

common type at the monument (Reneau 1995). In 2005, 

scoping participants identified the cliffs above the visitor 

center at the monument as susceptible to rockfall. 

Additionally, the area along the park road, referred to 

as the “big curve,” on the way to the visitor center has 

rockfall hazards (National Park Service 2005). 

In March 2014, Eric Bilderback (NPS Geologic 

Resources Division) responded to a technical assistance 

request from monument staff to assess rockfall hazards 

at the headquarters area and along the Main Loop 

Trail, which leads from the visitor center and includes 

the Nature Trail. Potential mitigation measures that 

could reduce the risk for employees stationed at 

headquarters include avoidance, for example, reducing 

or removing people from the hazard area. Other options 

include targeted scaling of boulders that threaten 

the headquarters building or constructing a rockfall 

protection barrier. Though effective, the latter can 

be expensive; the rockfall protection barrier in the 

maintenance area at Zion National Park is 80 m (250 ft) 

long and cost about $500,000 (Bilderback 2014).

Bilderback (2014) suggested that monument staff could 

educate visitors about the rockfall hazard along the 

Main Loop Trail using simple warning signs at the trail 

head and/or distributing pamphlets at the visitor center. 

Bilderback (2014) also suggested rockfall monitoring 

along the Main Loop Trail, which would include 

recording the date, approximate time, and weather 

conditions of a rockfall event; taking photographs; and 

documenting the location of the event with geographic 

positioning system (GPS) coordinates, which could 

be stored as GIS or tabular data in a spreadsheet. Data 

acquired during rockfall monitoring could help refine 

understanding of the conditions that are conducive to 

rockfall events at the monument, in turn, leading to a 

policy that would directly reduce risk to individuals 

(Bilderback 2014). 

Seismic Activity

In Bandelier National Monument, the Pajarito fault 

zone defines the local, western boundary of the Rio 

Grande rift (see “Rio Grande Rift” section). Holocene 

movements and historic seismicity indicate that the fault 

zone is active (Gardner and House 1987; Gardner et al. 

1990). In the last 1.25 million years, since the Tshirege 

Member was emplaced, a total of 200 m (660 ft) of 

displacement has occurred along the fault zone (Goff 

et al. 2005b). Earthquake magnitude and recurrence 

intervals along the fault zone are poorly constrained, 

but available data suggest that earthquakes of magnitude 

6.5 to 7 may occur at intervals of 10,000 to 60,000 years 

(Wong et al. 1995).

The most recent surface-rupturing earthquake on 

the Pajarito fault zone occurred between 2,200 and 

1,400 years ago (McCalpin 1998). Although strong 

earthquakes have occurred in historic times (described 

below), no historic surface-rupturing earthquakes have 

occurred (Olig et al. 1996). Two other surface ruptures 

have been documented in the fault system: one at 

10,900 to 9,000 years ago, and the other at 6,400 to 4,200 

years ago (Jamie N. Gardner, Los Alamos National 

Laboratory, geologist, unpublished data as documented 

in Kelley et al. 2007, p. 101). 

The most recent relatively large earthquake in the area 

with strong local effects occurred on 18 May 1918 in 

Santa Fe County. At the town of Cerrillos, people were 

thrown off their feet and fallen plaster was reported, 

indicating Modified Mercalli Intensities of VII to VIII 

(estimated magnitude 6.0 or greater on the Richter 

scale) (US Geological Survey 2013). In the 1990s, three 

small earthquakes on the Pajarito fault zone were felt 

throughout the area with intensities as high as Modified 

Mercalli Intensity VI (estimated magnitude 5.0) 

(Gardner and House 1994, 1999). 

A search of the USGS earthquake archive

(http://earthquake.usgs.gov/earthquakes/search/; 

accessed 4 September 2014) for Bandelier National 

Monument—using primary latitude and longitude 

in decimal degrees, 35.7883593 and -106.3028053, 

respectively—revealed three documented earthquakes 

since 2000: (1) magnitude 3.0 on 15 August 2007, (2) 

magnitude 2.7 on 7 February 2011, and (3) magnitude 

3.5 on 17 October 2011. The probability of a moderate 

earthquake (magnitude 5.0 or greater) occurring in the 

next century at Bandelier National Monument is more 

than 50% (http://geohazards.usgs.gov/eqprob/2009/

index.php; accessed 17 September 2014). An 

earthquake of this size or greater near the monument 

would cause significant damage to facilities and 

probably widespread rockfall in the canyons (National 

Park Service 2014a).
39

No data are available to evaluate the importance 

of seismic events on rockfall at the monument, but 

addressing this lack of information seems significant, 

given the active Pajarito fault zone crosses the 

monument. Seismic activity along the Pajarito fault zone 

is also of interest to Los Alamos National Laboratory 

for similar geologic hazard planning (Bilderback 2014). 

Thus any opportunities to collaborate with Los Alamos 

National Laboratory on research that could refine 

NPS understanding of the fault zone should be fully 

evaluated because the results of such a study could have 

bearing on park planning (Bilderback 2014).

In the chapter in Geological Monitoring about seismic 

monitoring, Braile (2009) described the following 

methods and vital signs: (1) monitoring earthquakes,

(2) analysis and statistics of earthquake activity,

(3) analysis of historical and prehistoric earthquake 

activity, (4) earthquake risk estimation, (5) geodetic 

monitoring and ground deformation, and

(6) geomorphic and geologic indications of active 

tectonics. The NPS Geologic Resources Division 

Seismic Monitoring and USGS Earthquakes Hazards 

websites provide more information (see http://go.nps.

gov/seismic_monitoring and http://earthquake.usgs.

gov/; accessed 21 January 2015).

Cavate Deterioration

As described in the “Bandelier Tuff” section, most 

cavates were excavated into the lower part of subunit 

Qtb1 of the Tshirege Member (fig. 10). Ancestral 

Puebloans took advantage of preexisting holes to 

hollow out cavates. More than 1,000 cavates were 

constructed in Frijoles Canyon. Gaining a better 

understanding of the material (i.e., Bandelier Tuff) in 

which the cavates occur will assist in the preservation of 

these fundamental resources.

Preliminary geomorphic assessment of cavates and cliff 

bases in Frijoles Canyon revealed that deterioration of 

the Bandelier Tuff occurs primarily through small-scale 

spalling and granular erosion, and to a lesser extent 

from large-scale rockfalls (Bass Rivera and Meyer 2009). 

Discharge of water from the vadose zone at the cliff 

base, capillary rise of moisture into the tuff, and surfacewater flow down the cliff face, which often streams 

directly into the cavates through entrances, smoke 

holes, and vents, are the primary processes contributing 

to deterioration of cavates (Bass Rivera and Meyer 

2009). This finding corroborates condition-assessment 

data that revealed that cavates on the ground level and 

in contact with talus slopes are generally more eroded 

and in poorer condition than those higher in the cliff 

(Bass Rivera and Meyer 2009). It also complements 

findings by McMillan et al. (2011), which suggested 

that groundwater percolation from the mesa top is not 

an important erosive process in Bandelier National 

Monument.

Moisture infiltration (from the bottom up) is probably 

combined with other physical processes that accelerate 

tuff disintegration and loss (Bass Rivera and Meyer 

2009). Physical processes likely include dissolution 

and crystallization of salts in the bedrock, diurnaltemperature changes, wet–dry cycling, windblown 

particle abrasion, and freeze–thaw cycles. Research into 

the effects of these processes on the Bandelier Tuff has 

begun. For example, Riggins et al. (2009) conducted 

weathering experiments on samples of the Tshirege 

Member. In freeze–thaw experiments, samples were 

immersed in water before being frozen. A significant 

loss of cohesion resulted in the disintegration of all 

samples after just six freeze–thaw cycles. 

Heating experiments conducted by Riggins et al. 

(2009) involved heating separate pieces of unaltered 

tuff to 300oC (572°F), 400oC (772°F), 500oC (932°F), 

and 600oC (1,112°F). Interestingly, all samples 

experienced increased surficial cohesion. This finding 

has a correlation to archeological observations that 

builders likely heated the interior of chambers with 

a fire (Bass Rivera and Meyer 2009). Thus, Ancestral 

Puebloans may have taken steps to actively reduce 

cavate deterioration. Additionally, studies revealed that 

soot deposits on the ceiling increase the coherence of 

freshly excavated surfaces (Riggins et. al. 2009). The 

exceptional preservation of some cavates is due in part 

to this sooty layer (Bass Rivera and Meyer 2009). 

Since 2000, the National Park Service Vanishing 

Treasures Program has been working to preserve 

the cavates at Bandelier National Monument. The 

Frijoles Canyon Cavate Pueblo Conservation Project 

administered by the Vanishing Treasures Program 

is a multidisciplinary, multiphase project set up to 

document the cavates and develop a conservation 

plan for their long-term protection. To this end, the 

project has initiated field and laboratory testing, 

materials analysis, detailed graphic documentation, 

environmental monitoring, and implementation of 
40

conservation treatments. Studies that examine the 

causes of cavate deterioration, both at the landscape 

level and in individual cavates, are significant for the 

project (Bass Rivera and Meyer 2006). Completion of 

a cavate conservation plan is a medium priority for the 

monument (National Park Service 2015).

Volcano Hazards

No eruptions as large as the ones that formed the Valles 

or Toledo calderas have occurred anywhere in the world 

in historic time. Only six such eruptions have occurred 

in the United States during the current geologic period 

(Quaternary Period; fig. 1). These include the last two 

Bandelier Tuff eruptions; three of the other eruptions 

were from Yellowstone, and one was from Long Valley, 

California. 

Another caldera-forming eruption in the Jemez 

Mountains volcanic field is unlikely (Goff et al. 2011). 

Far more probable are smaller, but still potentially 

explosive, eruptions similar to those that occurred 

in Valles caldera 60,000–40,000 years ago. These 

eruptions produced the Valles Rhyolite, including 

the El Cajete pyroclastic beds (Qvec), which occur 

in Bandelier National Monument. Consequences of 

such an event would likely be localized, resulting in 

the development of a lava dome (fig. 5) in the caldera 

or small-volume pyroclastic flows within the caldera 

and its stream drainages (fig. 36). If future eruptions 

emanated from a vent in the eastern part of Valles 

caldera, pyroclastic flows would likely impact Bandelier 

National Monument (Walkup 2013). In addition, ash 

fall beyond the caldera’s rim is a potential hazard (Goff 

et al. 2011). Bandelier National Monument would 

probably experience ash fall regardless of where in the 

caldera an eruption took place (Walkup 2013). Smaller 

eruptions are likely to have relatively small amounts of 

ash associated with them. However, even minor ash fall 

can create hazards with respect to air quality and air 

travel (Walkup 2013). Experience with the eruption of 

Mount St. Helens in 1980 indicates that as little as 0.5 

cm (0.2 in) of ash is sufficient to slow vehicle traffic to 

a crawl and close businesses for one to two weeks (US 

Geological Survey 2012). 

During an eruption in Valles caldera, volcanic 

projectiles ranging from lapilli to large volcanic bombs 

would be a significant hazard in areas adjacent to a 

volcanic vent (fig. 36). Projectiles are a localized hazard, 

but very large rocks (“bombs”) can be thrown out of an 

erupting volcano if the eruption has sufficient power, 

and even small rock fragments can be lethal and cause 

injury at distances of as much as 5 km (3 mi) from a vent 

(Walkup 2013).

Although the prediction of the timing and outcome of a 

volcanic eruption is not precise, monitoring can detect 

changes in a volcano’s behavior that precede impending 

eruptions. Past experience at Mount St. Helens and 

other volcanoes shows that ascending magma produces 

earthquakes as it pushes its way to the surface, thus 

giving local residents ample warning of an impending 

volcanic eruption (Goff 2009). Other indicators of 

a pending eruption might be ground deformation, 

increased hot spring or fumarolic activity, and plumes 

of smoke or ash rising from existing vents or new holes 

(Goff 2009).

Wolff and Gardner (1995) recommended geophysical 

monitoring of the Jemez Mountains area, so that if an 

eruption were to occur, forewarning would be possible. 

In the Geological Monitoring chapter about volcanoes, 

Smith et al. (2009) described seven vital signs and 

methodologies for understanding and monitoring 

volcanoes: (1) earthquake activity, 

(2) ground deformation, (3) emission at ground level, 

(4) emission of gas plumes and ash clouds,

(5) hydrologic activity, and (6) slope instability. This 

information may be of interest and use to managers at 

Bandelier National Monument. At present, no seismic 

monitoring stations occur within Bandelier National 

Monument (Walkup 2013). However, Yellowstone 

Volcano Observatory monitors volcanic activity in New 

Mexico, as well as Montana, Wyoming, Colorado, and 

Utah (see http://volcanoes.usgs.gov/observatories/yvo/; 

accessed 19 May 2015). 

Cochiti Dam and Reservoir 

Cochiti Dam is 10 km (7 mi) downstream from 

Bandelier National Monument (figs. 4 and 6). Originally 

constructed in 1935, the “rolled earth” dam was 

enlarged and redesigned in 1973 and is now more than 

8 km (5 mi) wide and 80 m (250 ft) high. Its primary 

purpose is flood and sediment control, holding back 

water and sediment from the Rio Grande (river). 

Seasonally (primarily during spring runoff), water 

inundates the lower elevations of White Rock Canyon, 

including the mouth of every canyon in Bandelier 

National Monument (Mott 1999). Temporary flooding 

of about 140 ha (350 ac) of NPS lands upstream of 
41

Figure 36. Schematic illustration of volcano hazards. Future volcano hazards that could affect Bandelier National 

Monument include the construction of a lava dome in Valles caldera, local pyroclastic flows, ash fall, and ejection of 

bombs. US Geological Survey graphic, available at http://pubs.usgs.gov/gip/64/gip64.pdf (accessed 23 September 2014).
42

the dam during the spring runoff period is allowed 

under a 1977 memorandum of understanding (MOU) 

between the National Park Service and US Army 

Corps of Engineers. This MOU permits a maximum 

flood-control contour of 1,665.9 m (5,465.5 ft) (Weeks 

2007). Significant for monument resources, however, 

flooding has exceeded “temporary” time frames and 

created resource impacts not anticipated by the MOU 

signatories (Mott 1999). GRI scoping and conference 

call participants identified extended periods of water 

holding as an area of concern. Notable water holding 

occurred during high runoff periods of 1985–1988.

Water storage has caused the following impacts 

in Bandelier National Monument: loss of native 

vegetation, including the burial and extirpation of six 

plant species previously found associated with springs; 

introduction of exotic plant species, including tamarisk 

(Tamarix spp.); submergence of cultural sites; the 

general degradation of the area through deposition 

of debris; and slumping of saturated canyon-wall 

colluvium (Allen et al. 1993). The final impact in this 

list is of particular interest for a geologic resources 

inventory. Although most of the landslides (Qls) in the 

Cochiti Dam quadrangle are inactive, Dethier et al. 

(2011) identified lake drawdown after high levels in the 

mid-1980s as the cause of reactivated major slides along 

the western margin of Cochiti Reservoir (see Map Unit 

Properties Table, in pocket; and GRI GIS data).

Silting is another geologically related issue at Cochiti 

Reservoir. Silting within Cochiti Reservoir’s backwaters 

effectively buried most of the native, high-quality 

riparian areas in the monument, and deposition 

of layers of river sand and silt provided a favorable 

medium for pioneer plant succession, including a 

variety of introduced agricultural weeds and riparian 

exotics (Potter 1981).

In addition, upstream sediment trapped behind the 

dam, is “silting up” the reservoir and reducing its 

capacity (Weeks 2007). The average sedimentation rate 

is 1.467 million m3

 (1,189 acre-feet) per year (Gallegos 

1998). By 1998, an estimated 33.725 million m3 (27,341 

acre-feet) of sediment had accumulated, utilizing 27% 

of the reservoir’s 130 million m3 (105,000 acre-feet) 

sediment reserve. At that rate, the designed storage 

volume for sediment will be fully used by 2063, and 

sediment will completely fill the reservoir in about 500 

years (Allen 1989). In some National Park System units, 

such as Bighorn Canyon National Recreation Area (see 

the GRI report by KellerLynn 2011), silting up of a 

reservoir is a primary management concern. This is not 

presently a concern, however, for Bandelier National 

Monument. 

Disturbed Land Restoration

Disturbed land restoration is the process of restoring 

lands to unimpaired natural conditions where natural 

conditions and processes have been impacted by 

facilities, roads, mines, dams, abandoned campgrounds, 

or other development, and/or by agricultural 

practices such as farming, grazing, timber harvest, 

and abandoned irrigation ditches. The NPS Geologic 

Resources Division assists park managers with 

disturbed land restoration in the National Park System 

(see http://go.nps.gov/grd_dlr; accessed 21 January 

2015). 

GRI scoping participants identified two sites near 

the amphitheater area at the monument that may be 

candidates for disturbed land restoration (National 

Park Service 2005). Referred to as “Amphitheater 

Landfill” and “Tyuonyi Dump Site,” the sites were an 

outcome of quarrying by the Civilian Conservation 

Corps (CCC) to obtain materials for road construction 

and building. Following quarrying activities, the sites 

were used for waste disposal by the US Forest Service 

(which administered the monument during the CCC 

era), Atomic Energy Commission (during World War II 

when the monument was closed to the public, and the 

lodge housed Manhattan Project scientists and military 

personnel), the New Mexico Highway Department, 

and most recently, the National Park Service (from the 

1950s until the 1970s). 

Kleinkauf (2012) provided a preliminary assessment 

and site inspection of these sites, and found that the 

“landfill” contains a variety of common household 

refuse (e.g., discarded appliances and trash) and debris 

from the CCC quarry operations and construction 

projects. The “dump site” contains discarded 

construction materials from the monument entrance 

road, headquarters, and lodge, and subsequent 

operation of these facilities. 

Investigators collected samples from both sites for 

analysis of target compound list (TCL) volatile and 

semivolatile organic compounds, total petroleum 

hydrocarbons (TPH) gasoline and diesel range organics, 
43

and target analyte list (TAL) metals and mercury. 

Although contaminants were found, none were detected 

at levels above background mean concentrations for 

New Mexico at either site (Kleinkauf 2012). Thus the 

preliminary assessment and site inspection concluded 

that the disposal of municipal waste had “little effect” 

[on human or environmental health] at either site 

(Kleinkauf 2012, p. 9 and 10). 

Kleinkauf (2012) noted the proximity of the sites to 

visitor use areas and suggested that removal would be 

consistent with the NPS mission. Furthermore, removal 

would preclude the possibility of future problems 

or safety concerns related to exposure of buried 

waste during heavy rains or flooding. According to 

Kleinkauf (2012), removal would be less costly than a 

full investigation and site characterization. Moreover, a 

full investigation, which would require excavation, may 

not be possible at the Tyuonyi Dump Site if the site was 

deemed eligible for the National Register of Historic 

Places. Notably, the dump site was considered “not 

significant” under the eligibility criteria of the National 

Register of Historic Places in 1994, but since then was 

re-evaluated and may be eligible under criterion (d), 

which deems sites eligible “that have yielded, or may be 

likely to yield, information important in prehistory or 

history” (http://www.achp.gov/nrcriteria.html; accessed 

30 December 2014) (Kleinkauf 2012). The National 

Park Service is more likely to remove or restore a site 

considered “not significant.”

At present, both sites remain in place, with no plan for 

removal. In short, the project has not risen to a level that 

calls for action relative to other resource management 

issues (Barbara Judy, Bandelier National Monument, 

chief of resources, email communication, 12 September 

2014).

Paleontological Resource Inventory, 

Monitoring, and Protection

Tweet et al. (2009) compiled paleontological 

information for the Southern Colorado Plateau 

Network, including Bandelier National Monument, 

but did not conduct a field-based inventory. Managers 

at Bandelier National Monument are encouraged 

to contact the NPS Geologic Resources Division 

for assistance with such an inventory, which would 

provide detailed, site-specific descriptions and resource 

management recommendations. The Tweet et al. (2009) 

publication included preliminary resurce management 

recommendations. In the meantime, monument 

managers may find the chapter about monitoring in situ 

paleontological resources in Geological Monitoring of 

interest and use. In their chapter, Santucci et al. (2009) 

outlined potential threats to fossil resources: (1) erosion 

(geologic factors), (2) erosion (climatic factors),

(3) catastrophic geohazards, (4) hydrology/bathymetry, 

and (5) human access/public use.

All paleontological resources are non-renewable and 

subject to science-informed inventory, monitoring, 

protection, and interpretation as outlined by the 

2009 Paleontological Resources Preservation Act (see 

Appendix B). As of August 2015, Department of the 

Interior regulations associated with the act were being 

developed.

45

Geologic History

This chapter describes the chronology of geologic events that formed the present landscape of Bandelier 

National Monument.

Bandelier National Monument is in the Jemez 

Mountains volcanic field, which is best known for 

the Bandelier Tuff and Valles caldera (see “Bandelier 

Tuff” and “Valles Caldera” sections). The volcanic field 

became active about 14 million years ago (Miocene 

Epoch; fig. 1), though the earliest volcanism in the area 

began about 25 million years ago (Oligocene Epoch) 

and is contemporaneous with development of the 

Rio Grande rift. About 3 million years ago (Pliocene 

Epoch), several peripheral volcanic fields were active 

to the north, south, and east of the Jemez Mountains 

volcanic field. All the while the Rio Grande rift was 

stretching apart, and the ancestral Rio Grande (river) 

flowed within it.

Rio Grande Rift

As Earth’s crust began pulling apart in the northern 

part of the Rio Grande rift, the Española basin dropped 

down along normal faults (fig. 16). Sediment of the 

Santa Fe Group, which is dated to about 25 million 

years ago (WoldeGabriel et al. 2006), began filling 

the basin. Volcanic activity and fluvial activity of the 

ancestral Rio Grande (river) contributed to basin filling. 

Sedimentation has continued to the present day, though 

modern sediments are not included in the Santa Fe 

Group (see “Landscape Evolution” section). Volcanic 

rocks interbedded with sedimentary deposits in the 

lower part of the Santa Fe Group record early volcanic 

activity in the Bandelier area.

Peripheral Volcanism

Volcanic rocks peripheral to the Jemez Mountains 

volcanic field occur within and on the boundary of the 

Rio Grande rift. Three peripheral volcanic fields—El 

Alto to the north, Santa Ana Mesa to the south, and 

Cerros del Rio to the east (fig. 6)—started erupting 

about 4.6 million years ago and mostly ended about 

2.0 million years ago (Bachman and Mehnert 1978; 

Baldridge et al. 1980). The Cerros del Rio volcanic field 

erupted mainly between 2.7 million and 1.1 million 

years ago (Thompson et al. 2011). Cerros del Rio 

volcanic rocks (QTvrc) record this volcanic activity at 

Bandelier National Monument (see “Cerros del Rio 

Volcanic Rocks” section).

Jemez Mountains Volcanic Field

The Jemez Mountains volcanic field began erupting 

about 14 million years ago. The rocks of the field 

occur in two major groups: (1) Keres, which erupted 

14 million to 2 million years ago; and (2) Tewa, which 

erupted 1.8 million to 40,000 years ago. The Canovas 

Canyon Rhyolite, Bearhead Rhyolite, Paliza Canyon 

Formation, and Tschicoma Formation (see Map Unit 

Properties Table, in pocket) are rocks of the Keres 

Group within the monument.

The Tewa Group is particularly important for Bandelier 

National Monument because during “Tewa time” 

volcanism reached a climax with two caldera-forming 

eruptions of Bandelier Tuff (fig. 8). The first event, 

which corresponds to the collapse of Toledo caldera, 

deposited the Otowi Member (Qbo), 1.61 million years 

ago. The second deposited the Tshirege Member (Qbt) 

and created the Valles caldera 1.25 million years ago. 

These explosions were at a scale never witnessed by 

humans (Dunbar 2010a). Eruption of Bandelier Tuff 

effectively buried most of the former topography, twice, 

reshaping the landscape between Sierra de los Valles 

and the Rio Grande.

A period of about 400,000 years separated the eruptions 

of the Otowi and Tshirege members. During this 

time, rhyolite of the Cerro Toledo Formation erupted 

to form domes, such as Rabbit Mountain, in Toledo 

caldera. Cerro Toledo rhyolites represent post–caldera 

collapse volcanism associated with the formation of 

the Toledo caldera. Moreover, Cerro Toledo deposits 

record an interval of rapid landscape evolution when 

poorly welded Otowi Member and other rock units 

were eroded by streams into a landscape of mesas and 

canyons rimmed by sloping hillsides and tent rocks 

(Jacobs and Kelley 2007).

Soon after the eruption of the Tshirege Member 

and within 54,000 years of collapse of Valles caldera 

(Phillips et al. 2007), the floor of the caldera, which is 

composed of Tshirege Member, began to rise up more 

than 1,000 m (3,300 ft), creating what would become 

the text book example of a resurgent caldera (fig. 8). 
46

The highest dome in Valles caldera—Redondo Peak—

represents this uplift (fig. 37).

Renewed volcanism of extruding Valles Rhyolite 

accompanied the development of the resurgent caldera 

(fig. 8). Rhyolitic lava domes erupted around the 

perimeter of the uplifted caldera floor (fig. 38). These 

domes create a striking display in satellite imagery 

(fig. 6), digital elevation models (fig. 7), and geologic 

maps (see poster, in pocket). Cerro del Medio, which 

was emplaced about 1.23 million years ago (Phillips 

et al. 2007), was the first rhyolite dome to erupt (fig. 

38). The domes become progressively younger in 

a counterclockwise direction (Dunbar 2005). The 

youngest domes—South Mountain and Cerro La Jara 

(figs. 37 and 38)—erupted about 52,000 years ago (Goff 

2009). 

Materials from Valles Rhyolite eruptions are 

interlayered with lake deposits, indicating that the 

caldera has been at least partially filled by water 

since its collapse. Past shorelines of these lakes are 

included in the GRI GIS data set and delineated as 

“paleoshorelines.”

Figure 37. Photograph of Valle Grande. Valles Grande is the largest valley in Valles caldera. Cerro La Jara—a rhyolite 

dome that formed in the caldera about 540,000 years ago—rises above the meadow floor. In the background, a flank 

of Redondo Peak ultimately rises to 3,434 m (11,266 ft) above sea level, the high point in Valles caldera. Redondo Peak 

represents the resurgent caldera; the uplifted floor is composed primarily of the Tshirege Member of the Bandelier 

Tuff. Photograph by Brian0918 on Wikimedia Commons, available at https://commons.wikimedia.org/wiki/File:Valle_

Grande_dome.jpg (accessed 14 August 2014).

Figure 38 (facing page). Geologic sketch map of Valles caldera. The rocks of Valles caldera are from the Tewa Group. 

The Tshirege Member of Bandelier Tuff, represented by the background color on this figure, filled the caldera and 

built up adjacent plateaus. The floor of Valles caldera was uplifted during caldera resurgence (fig. 8); Redondo Peak 

(R) represents this resurgence. Faults (bold black lines) split the caldera floor and adjacent plateaus. Normal faults 

bound the Redondo Creek graben (RG) at the center of the caldera. Plugs of Cerro Rubio dacite (green) are part of 

the Tschicoma Formation, which predates eruption of Bandelier Tuff. No Cerro Rubio dacite occurs within Bandelier 

National Monument, although other members of the Tschicoma Formation do. Cerro Toledo Formation (pink) 

postdates the Toledo caldera (TC), occurring between the eruptions of Otowi and Tshirege members of Bandelier Tuff. 

Features composed of Cerro Toledo Formation (rhyolite) include Cerro Toledo (CT) dome, two Los Posos (LP) domes, 

Rabbit Mountain (RM), and Paseo del Norte (PN). Valles Rhyolite (yellow) erupted as domes surrounding the uplifted 

caldera floor. These domes are Cerro del Medio (CdM), which erupted first; followed in a counterclockwise direction 

by the eruption of Cerro del Abrigo (A), Cerro Santa Rosa (SR), Cerro San Luis (SL), Cerro Seco (SE), and San Antonio 

(SA) Mountain. In the southern part of the caldera, South Mountain (SM) dome and flow, and Cerro La Jara (CLJ) 

dome erupted last in the Valles Rhyolite series. El Cajete pyroclastic beds (purple), also part of Valles Rhyolite, erupted 

from the El Cajete vent in the caldera and spread across the landscape between 60,000 and 50,000 years ago. The 

most recent eruption in the caldera deposited the Banco Bonito flow (blue) about 45,000–37,000 years ago. Graphic 

by Jason Kenworthy (NPS Geologic Resources Division) after Goff (2009, figure 26), using GRI GIS data for Bandelier 

National Monument. Base imagery from ESRI World Imagery (accessed 17 February 2015).
47
48

About 60,000–50,000 years ago, eruption of the El 

Cajete vent in the southern part of the caldera (figs. 

23 and 38) launched a new cycle of volcanism in the 

Jemez Mountains volcanic field (Wolff and Gardner 

1995; Wolff et al. 1996). Along with this new stage of 

magmatism came the possibility of future explosive 

eruptions in the caldera (see “Volcano Hazards” 

section). The most recent eruption in the caldera 

deposited the Banco Bonito lava flows about 45,000–

37,000 years ago (Kelley et al. 2013). These flows do not 

occur in Bandelier National Monument (fig. 38).

Landscape Evolution

Incision of canyons since the eruption of the Tshirege 

Member has produced many mesas consisting of 

Bandelier Tuff, including Pajarito Plateau east of Valles 

caldera and home to Bandelier National Monument. 

Bandelier Tuff is beautifully exposed in the vertical 

canyon walls of the Pajarito Plateau (Goff 2009).

The dated Tshirege Member of Bandelier Tuff provides 

an excellent temporal constraint for valley incision and 

landscape evolution (Reneau 2000). After eruption 

of the Tshirege Member (Qbt) but before eruption of 

the El Cajete pyroclastic beds (Qvec), which like the 

Tshirege Member is a significant time-stratigraphic 

marker in the area (Reneau et al. 1996), the Rio Grande 

and its tributaries experienced net incision separated 

by episodes of aggradation. At the monument, levels of 

alluvial deposits—in descending order, from oldest to 

youngest: Qa2, Qa3, and Qa4 (see Map Unit Properties 

Table, in pocket)—mark the episodic incision of the Rio 

Grande. For example, when Qa2 was deposited, the Rio 

Grande was flowing at an elevation 50 to 70 m (160 to 

230 ft) higher than at present. On the flanks of the Jemez 

Mountains, many levels of piedmont alluvial deposits 

(Qp2, Qp3, and Qp4) grade towards the Rio Grande 

valley. These deposits record how slopes have changed 

over time. Terrace gravel (Qt) above present stream 

channels, beds of sand (Qa5) along the Rio Grande, 

alluvial fan deposits (Qfa) within and at the mouths of 

valleys, and alluvium (Qal) at canyon bottoms record 

the fluvial history at the monument to the present day. 

Beyond stream channels, the following units document 

ongoing changes to the Bandelier landscape: colluvium 

(Qc); landslide deposits (Qls), some as old as the 

Tshirege Member; and sheetwash deposits (Qpa; 

deposited by overland flow of water). Slopes marked 

by these deposits have been subject to earthquakes, 

erosion, and slope movements. Along with streamflow, 

these geologic agents are in league to change the 

landscape of Bandelier National Monument, usually 

gradually but sometimes suddenly and swiftly (see 

“Fire, Fluvial Geomorphology, and Slope Movements” 

section). 

No evidence for glaciation has been reported in the 

Jemez Mountains, so glaciers are a geologic agent 

missing from the Bandelier landscape. Boulder fields 

(Qrx), however, which Goff et al. (2011) mapped at the 

northern boundary of Bandelier National Monument, 

delineate high-elevation features associated with 

periglacial conditions. For instance, the nearby Sangre 

de Cristo Mountains, display much Pleistocene ice-age 

evidence (Reneau and McDonald 1996).

Humans on the Landscape

Geologic features of the Jemez Mountains volcanic field 

affected the people who lived on the Pajarito Plateau 

in a variety of ways. Ancestral Puebloans hollowed out 

cavates from Bandelier Tuff, taking advantage of natural 

cavities and further excavating them for habitation and 

storage, and ancient travelers created trail systems in 

the tuff (see “Features in Bandelier Tuff” section). Also 

volcanoes and lava flows yielded lithic resources such 

as obsidian, dacite, and chert (see “Lithic Resources” 

section). Furthermore, the locations of Puebloan 

communities on the Pajarito Plateau correlate to the 

presence of El Cajete pyroclastic beds (Qvec). Because 

El Cajete pumice retains water, it was important for 

prehistoric farming (see “El Cajete Pyroclastic Beds” 

section). For nearly 500 years, pumice fields enabled 

Puebloan farmers to survive on the slopes of the Jemez 

Mountains, making labor intensive construction of 

moisture-trapping features such as terraces, check 

dams, grid gardens, and cobble mulching unnecessary 

under most conditions (Gauthier et al. 2007). 

Bandelier National Monument provides ample and 

diverse evidence of the importance of volcanic features 

to create a landscape well suited for prehistoric 

Puebloan civilization (Dunbar 2010a), as well as 

habitation to the present day. A succession of Spanish 

land grants, homesteads, scattered ranches, logging 

operations, and parts of the World War II Manhattan 

Project followed ancient pueblos and cliff dwellings on 

the Bandelier landscape. 
49

Geologic Map Data

This chapter summarizes the geologic map data available for Bandelier National Monument. A poster 

(in pocket) displays the GRI GIS data draped over imagery of the monument and surrounding area. 

The Map Unit Properties Table (in pocket) summarizes this report’s content for each geologic map unit 

within the Bandelier National Monument. Complete GIS data are available at the GRI publications 

website: http://go.nps.gov/gripubs.

Geologic Maps

Geologic maps facilitate an understanding of an area’s 

geologic framework and the evolution of its present 

landscape. Using designated colors and symbols, these 

maps portray the spatial distribution and temporal 

relationships of rocks and unconsolidated deposits. 

Geologic maps can be divided into two primary types: 

surficial and bedrock. Surficial geologic maps typically 

encompass deposits that are unconsolidated and 

formed during the past 2.6 million years (Quaternary 

Period; fig. 1). Surficial map units are differentiated 

by geologic process or depositional environment. 

Bedrock geologic maps encompass older, typically 

more consolidated sedimentary, metamorphic, and/

or igneous rocks. Bedrock map units are differentiated 

based on age and/or rock type.

Geologic maps often depict geomorphic features, 

structural interpretations (such as faults or folds), 

and locations of past geologic hazards that may be 

susceptible to future activity. Anthropogenic features 

such as mines or quarries, as well as observation or 

collection locations, may be indicated on geologic 

maps. The American Geosciences Institute website, 

http://www.americangeosciences.org/environment/

publications/mapping (accessed 21 January 2015), 

provides more information about geologic maps and 

their uses. 

Source Maps

The GRI team digitizes paper maps and converts digital 

data to conform to the GRI GIS data model. GRI digital 

geologic map products include essential elements 

of the source maps such as map unit descriptions, a 

correlation chart of units, a map legend, map notes, 

references, and figures. The GRI team used the 

following sources to produce the GRI GIS data set for 

Bandelier National Monument. These sources also 

provided information for this report.

Dethier, D. P. 2003. Geologic map of the Puye quadrangle, Los 

Alamos, Rio Arriba, Sandoval, and Santa Fe counties, New 

Mexico (scale 1:24,000). Miscellaneous Field Studies Map 

MF-2419. US Geological Survey, Denver, Colorado. http://

pubs.usgs.gov/mf/2003/mf-2419/ (accessed 28 May 2014).

Dethier, D. P., R. A. Thompson, M. R. Hudson, S. A. Minor, 

and D. A. Sawyer. 2011. Geologic map of the Cochiti Dam 

quadrangle, Sandoval County, New Mexico (scale 1:24,000). 

Scientific Investigations Map SIM-3194. US Geological 

Survey, Denver, Colorado. http://pubs.usgs.gov/sim/3194/ 

(accessed 23 May 2014).

Goff, F., J. N. Gardner, and S. L. Reneau. 2002a. Geology of 

the Frijoles quadrangle, Los Alamos and Santa Fe counties, 

New Mexico (scale 1:24,000). Open-File Geologic Map 

OF-GM 42. New Mexico Bureau of Mines and Mineral 

Resources, Socorro, New Mexico. http://geoinfo.nmt.edu/

publications/maps/geologic/ofgm/details.cfml?Volume=42

(accessed 28 May 2014).

Goff, F., J. N. Gardner, S. L. Reneau, and C. J. Goff. 2005a. 

Geologic map of the Redondo Peak quadrangle, Sandoval 

County, New Mexico (scale 1:24,000). Open-File Geologic 

Map OF-GM 111. New Mexico Bureau of Geology 

and Mineral Resources, Socorro, New Mexico. http://

geoinfo.nmt.edu/publications/maps/geologic/ofgm/details.

cfml?Volume=111 (accessed 28 May 2014).

Goff, F., J. N. Gardner, S. L. Reneau, S. A. Kelley, K. A. 

Kempter, and J. R. Lawrence. 2011. Geologic map of the 

Valles caldera, Jemez Mountains, New Mexico (scale 

1:50,000). Geologic Map GM-79. New Mexico Bureau of 

Geology and Mineral Resources, Socorro, New Mexico.

Goff, F., S. L. Reneau, S. Lynch, C. J. Goff, J. N. Gardner, 

P. Drakos, and D. Katzman. 2005c. Geologic map of the 

Bland quadrangle, Los Alamos and Sandoval counties, 

New Mexico (scale 1:24,000). Open-File Geologic Map 

OF-GM-112. New Mexico Bureau of Geology and Mineral 

Resources, Socorro, New Mexico. http://geoinfo.nmt.edu/

publications/maps/geologic/ofgm/details.cfml?Volume=112 

(accessed 23 May 2014).

Kempter, K., G. R. Osburn, S. Kelley, M. Rampey, C. Ferguson, 

and J. Gardner. 2007. Geologic map of the Bear Springs 

Peak quadrangle, Sandoval County, New Mexico (scale 

1:24,000). Open-File Geologic Map OF-GM 74. New 

Mexico Bureau of Geology and Mineral Resources, 

Socorro, New Mexico. http://geoinfo.nmt.edu/publications/

maps/geologic/ofgm/details.cfml?Volume=74 (accessed 28 

May 2014).
50

Kempter, K. A., S. Kelley, J. N. Gardner, S. L. Reneau, D. E. 

Broxton, F. Goff, A. Levine, and C. Lewis. 1998. Geologic 

Map of the Guaje Mountain quadrangle, Los Alamos and 

Sandoval counties, New Mexico (scale 1:24,000). Open-File 

Geologic Map OF-GM 55. New Mexico Bureau of Geology 

and Mineral Resources, Socorro, New Mexico. http://

geoinfo.nmt.edu/publications/maps/geologic/ofgm/details.

cfml?volume=55 (accessed 28 May 2014).

Koning, D. J., and A. S. Read. 2010. Geologic map of the 

southern Española basin (scale 1:48,000). Open-File 

Report 531. New Mexico Bureau of Geology and Mineral 

Resources, Socorro, New Mexico. http://geoinfo.nmt.edu/

publications/openfile/details.cfml?Volume=531 (accessed 

23 May 2014).

Lynch, S. D., G. A. Smith, and A. J. Kuhle. 2005. Geologic map 

of the Canada quadrangle, Sandoval County, New Mexico 

(scale 1:24,000). Open-File Geologic Map OF-GM 85. 

New Mexico Bureau of Geology and Mineral Resources, 

Socorro, New Mexico. http://geoinfo.nmt.edu/publications/

maps/geologic/ofgm/details.cfml?Volume=85 (accessed 28 

May 2014).

Thompson, R. A., M. R. Hudson, R. R. Shroba, S. A. Minor, 

and D. A. Sawyer. 2011. Geologic map of the Montoso Peak 

quadrangle, Santa Fe and Sandoval counties, New Mexico 

(scale 1:24,000). Scientific Investigations Map SIM-3179. 

US Geological Survey, Reston, Virginia. http://pubs.usgs.

gov/sim/3179/ (accessed 28 May 2014).

GRI GIS Data

The GRI team implements a GIS data model that 

standardizes map deliverables. The data model is 

available at http://go.nps.gov/gridatamodel. This data 

model dictates GIS data structure, including layer 

architecture, feature attribution, and relationships 

within ESRI ArcGIS software. The GRI team digitized 

the data for Bandelier National Monument using data 

model version 2.1. The GRI Geologic Maps website, 

http://go.nps.gov/geomaps, provides more information 

about GRI map products. 

GRI digital geologic data are available through the NPS 

Integrated Resource Management Applications (IRMA) 

portal (https://irma.nps.gov/App/Portal/Home). Enter 

“GRI” as the search text and select a park.

The following components are part of the data set:

● A GIS readme file (band_gis_readme.pdf) 

that describes the GRI data formats, naming 

conventions, extraction instructions, use 

constraints, and contact information.

● Data in ESRI geodatabase GIS format;

● Layer files with feature symbology (table 2);

● Federal Geographic Data Committee–compliant 

metadata;

● An ancillary map information document (band_

geology.pdf) that contains information captured 

from source maps;

● An ESRI map document (band_geology.mxd) that 

displays the digital geologic data; and

● A KML/KMZ version of the data viewable in 

Google Earth (table 2).

GRI Map Poster

A poster of the GRI digital geologic data draped over a 

shaded relief image of the monument and surrounding 

area is included with this report (in pocket). Not all GIS 

feature classes are included on the poster, as indicated 

in table 2. Geographic information and features have 

been added to the poster. Digital elevation data and 

added geographic information are not included in the 

GRI GIS data set, but are available online from a variety 

of sources. Contact GRI staff for assistance locating 

these data.

Map Unit Properties Table

The Map Unit Properties Table (in pocket) lists the 

geologic time division, symbol, and a simplified 

description for each of the geologic map units within 

Bandelier National Monument. Following the structure 

of the report, the table summarizes the geologic features 

and processes, resource management issues, and 

geologic history associated with each map unit. 

Use Constraints

Graphic and written information provided in this 

report is not a substitute for site-specific investigations. 

Ground-disturbing activities should neither be 

permitted nor denied based on the information 

provided here. Please contact the GRI team with any 

questions.

Minor inaccuracies may exist regarding the locations 

of geologic features relative to other geologic or 

geographic features on the poster. Based on US 

National Map Accuracy Standards and source-map 

scales—primarily 1:24,000 but also 1:48,000 and 

1:50,000—geologic features represented in the geologic 

map data are horizontally within 12 m (40 ft), or 24 

m (80 ft) and 25 m (82 ft), of their true locations at 

1:24,000, 1:48,000, or 1:50,000, respectively.
51

Data Layer On Poster? Google Earth Layer?

Geologic Cross Section Lines No No

Geologic Attitude Observation Localities No No

Geologic Sample Localities No No

Mine Point Features No No

Volcanic Point Features (vents, fumaroles) Yes No

Geologic Point Features No No

Paleoshorelines No No

Volcanic Line Features Yes No

Hazard Feature Lines Yes No

Geologic Line Features No Yes

Map Symbology Yes No

Folds Yes Yes

Faults Yes Yes

Alteration and Metamorphic Area Boundaries No No

Alteration and Metamorphic Areas No Yes

Linear Dikes No Yes

Deformation Area Boundaries No No

Deformation Areas No Yes

Geologic Contacts No Yes

Geologic Units Yes Yes

Table 2. Data layers in the Bandelier National Monument GRI GIS data set

53

Glossary

These are brief definitions of selected geologic terms relevant to this report. Definitions are based on 

those in the American Geosciences Institute Glossary of Geology (5th edition; 2005). Additional terms 

are defined at http://geomaps.wr.usgs.gov/parks/misc/glossarya.html.

accretion. The addition of island-arc or continental material 

to a continent via collision, welding, or suturing at a 

convergent plate boundary. 

aggradation. The building up of Earth’s surface by 

depositional processes.

alluvial fan. A low, relatively flat to gently sloping, fanshaped mass of loose rock material deposited by a stream, 

especially in a semiarid region, where a stream issues from 

a canyon onto a plain or broad valley floor.

alluvial terrace. A stream terrace composed of 

unconsolidated alluvium produced by a rejuvenated 

stream via renewed downcutting of the floodplain or 

valley floor, or by the covering of a terrace with alluvium.

alluvium. Stream-deposited sediment.

amygdule. A gas cavity or vesicle in an igneous rock that has 

become filled with secondary minerals.

andesite. A volcanic rock characteristically medium dark in 

color and containing approximately 57%–63% silica and 

moderate amounts of iron and magnesium.

aphanitic. Describes the texture of fine-grained 

igneous rock in which different components are not 

distinguishable by the unaided eye.

aphyric. Describes the texture of a fine-grained igneous rock 

that lacks coarse crystals.

ash. Fine-grained material, less than 2 mm (0.08 in) across, 

ejected from a volcano.

ash fall. Airborne ash that falls from an eruption cloud, and 

the resulting deposit.

ash flow. A density current, generally a hot mixture of 

volcanic gases and tephra that travels across the ground 

surface; produced by the explosive disintegration of 

viscous lava in a volcanic center, or from a fissure or group 

of fissures. The solid materials contained in a typical 

ash flow are generally unsorted and ordinarily include 

volcanic dust, pumice, scoria, and blocks in addition to 

ash.

ash-flow tuff. A tuff deposited by an ash flow.

axial stream. The main stream of an intermontane valley, 

flowing in the deepest part of the valley parallel to it 

longest dimension. Also, a stream that follows a syncline 

or anticline.

backwater. A body of water that is parallel to a river but is 

stagnant or little affected by the river’s currents.

bank. A submerged ridge of sand in the sea, a lake, or a river, 

usually exposed during low tide or low water.

basalt. A volcanic rock that is characteristically dark in color 

(gray to black), contains approximately 53% silica or less, 

and is rich in iron and magnesium.

basaltic andesite. A volcanic rock that is commonly dark 

gray to black and contains approximately 53%–57% silica.

base level. The lowest level to which a stream channel can 

erode. The ultimate base level is sea level, but temporary, 

local base levels exist. 

basin (structural). A doubly plunging syncline in which rocks 

dip inward from all sides.

basin (sedimentary). Any depression, from continental to 

local scale, into which sediments are deposited.

bed. The smallest sedimentary stratigraphic unit, commonly 

ranging in thickness from about 1 cm (0.4 in) to 1 to 2 m 

(40 to 80 in) and distinguishable from beds above and 

below.

bedding. Depositional layering or stratification of 

sediments.

bedrock. Solid rock that underlies unconsolidated 

sedimentary deposits and soil.

biotite. A dark-colored, shiny silicate mineral (silicon + 

oxygen) of the mica group composed of magnesium and/

or iron, K(Mg,Fe)Si3

O10(OH)2; characterized by perfect 

cleavage, readily splitting into thin sheets.

block. A pyroclast ejected in a solid state with a diameter 

greater than 64 mm (2.5 in).

block (fault). A crustal unit bounded completely or partially 

by faults.

bomb. A viscous pyroclast ejected then shaped while in 

flight; commonly more than 64 mm (2.5 in) in diameter 

and with a hollow or vesicular interior.

braided stream. A sediment-clogged stream that forms 

multiple channels that divide and rejoin.

breccia. A coarse-grained, generally unsorted sedimentary 

rock consisting of cemented angular clasts more than 2 

mm (0.08 in) across. 

breccia (volcanic). A coarse-grained, generally unsorted 

volcanic rock consisting of partially welded angular 

fragments of ejected material.

burrow. A tubular or cylindrical hole or opening, made in 

originally soft or loose sediment by a mud-eating worm, 

mollusk, or other invertebrate; may be later filled with clay 

or sand and preserved.

caldera. A large, more-or-less circular, basin-shaped 

volcanic depression formed by collapse during an 

eruption.

calcite. A carbonate (carbon + oxygen) mineral of calcium, 

CaCO3

; calcium carbonate. It is the most abundant cave 

mineral.

capillary action. The action by which a fluid, such as water, is 

drawn up in small interstices or tubes as a result of surface 

tension.
54

cauldron. An inclusive term for all volcanic subsidence 

structures regardless of shape or size, depth of erosion, 

or connection with the surface; the term includes caldron 

subsidences and collapse calderas.

channel. The bed where a natural body of surface water 

flows or may flow. Also, a natural passageway or 

depression of perceptible extent containing continuously 

or periodically flowing water, or forming a connecting link 

between two bodies of water.

chert. An extremely hard sedimentary rock with conchoidal 

fracturing, consisting mostly of interlocking crystals of 

quartz. 

cinder. A glassy, vesicular, pyroclastic fragment that falls to 

the ground in an essentially solid condition.

cinder cone. A conical hill, commonly steep, ranging 

from tens to hundreds of meters tall, formed by the 

accumulation of solidified fragments of lava that fell 

around the vent during a basaltic or andesitic eruption. 

clay. Minerals and sedimentary fragments that are less than 

1/256 mm (0.00015 in) across.

clinopyroxene. A group name for pyroxene minerals that 

crystallize in the monoclinic system and sometimes 

contain considerable calcium with or without aluminum 

and the alkali metals. 

coarse-grained. Describes a crystalline rock and texture 

in which the individual minerals are relatively large, 

specifically an igneous rock whose particles have an 

average diameter greater than 5 mm (0.2 in). Also, 

describes sediment or sedimentary rock and texture in 

which the individual constituents are easily seen with the 

unaided eye, specifically sediment or rock whose particles 

have an average diameter greater than 2 mm (0.08 in).

cobble. A rock fragment larger than a pebble and smaller 

than a boulder, having a diameter in the range of 64–256 

mm (2.5–10 in), being somewhat rounded or otherwise 

modified by abrasion in the course of transport.

cohesion. The intermolecular attraction by which the 

elements of a body are held together.

colluvium. A loose, heterogeneous, and incoherent mass 

of rock fragments and soil material deposited via surface 

runoff or slow continuous downslope creep; usually 

collects at the base of a slope or hillside, but includes 

loose material covering hillsides.

conchoidal. Resembling the curve of a conch shell and 

used to describe a smoothly curved surface on a rock or 

mineral; characteristic of quartz and obsidian. 

conglomerate. A coarse-grained, generally unsorted, 

sedimentary rock consisting of cemented, rounded clasts 

larger than 2 mm (0.08 in) in diameter.

coprolite. Fossilized feces.

cross-bed. A single bed, inclined at an angle to the main 

planes of stratification; the term is commonly restricted to 

a bed that is more than 1 cm (0.4 in) thick.

cross-bedding. Uniform to highly varied sets of inclined 

beds deposited by wind or water that indicate flow 

conditions such as direction and depth. 

cross section. A graphic interpretation of geology, structure, 

or stratigraphy based on mapped and measured geologic 

extents and attitudes, depicted in a vertical plane (i.e., a 

cut or profile view).

crust. Earth’s outermost layer or shell. 

crystalline. Describes a regular, orderly, repeating geometric 

structural arrangement of atoms.

dacite. A volcanic rock that is characteristically light in 

color and contains approximately 63%–68% silica and 

moderate amounts of sodium and potassium. 

debris flow. A moving mass of rock fragments, soil, and 

mud, with more than half of the particles larger than sand 

size. Slow debris flows may move less that 1 m (3 ft) per 

year; rapid ones reach 160 kph (100 mph). 

deformation. The process of folding, faulting, shearing, or 

fabric development in rocks as a result of Earth stresses.

dendritic. Describes a branching pattern.

differential erosion. Erosion that occurs at irregular or 

varying rates due to differences in the resistance and 

hardness of surface material: softer and weaker rocks 

are rapidly worn away; harder and more resistant rocks 

remain to form ridges, hills, or mountains.

discharge. The rate of flow of surface water or groundwater 

at a given moment, expressed as volume per unit of time.

displacement. The relative movement of the two sides of a 

fault; also, the specific amount of such movement.

dome. Any smoothly rounded landform or rock mass; more 

specifically, an elliptical uplift in which rocks dip gently 

away in all directions. 

downcutting. Stream erosion in which cutting is directed 

primarily downward, as opposed to laterally.

drainage. The manner in which the waters of an area flow 

off in surface streams or subsurface conduits; also, the 

processes of surface drainage of water from an area by 

streamflow and sheet flow, and the removal of excess 

water from soil by downward flow.

drainage basin. A region or area bounded by a drainage 

divide and occupied by a drainage system, specifically 

the tract of country that gathers water originating as 

precipitation and contributes it to a particular stream 

channel or system of channels, or to a lake, reservoir, or 

other body of water.

dune. A low mound or ridge of sediment, usually sand, 

deposited by the wind. 

eolian. Describes materials formed, eroded, or deposited by 

or related to the action of wind. Also spelled “aeolian.”

ephemeral lake. A short-lived lake.

erosion. The general process or group of processes that 

loosen, dissolve, wear away, and simultaneously move 

from one place to another, the materials of Earth’s crust; 

includes weathering, solution, abrasive actions, and 

transportation, but usually excludes slope movements.

escarpment. A steep cliff or topographic step resulting from 

vertical displacement on a fault or as a result of slope 

movement or erosion. Synonymous with “scarp.”

explosive eruption. An energetic eruption that produces 

mainly ash, pumice, and fragmental ballistic debris. 
55

extension. Deformation of Earth’s crust whereby rocks are 

pulled apart. 

extrusion. The emission of lava onto Earth’s surface; also, 

the rock so formed.

extrusive. Describes an igneous rock that has been erupted 

onto the surface of the Earth. Extrusive rocks include lava 

flows and pyroclastic material such as volcanic ash.

facies. The depositional or environmental conditions 

reflected in the sedimentary structures, textures, 

mineralogy, fossils, and other components of a 

sedimentary rock.

fanglomerate. A sedimentary rock consisting of waterworn 

fragments of various sizes deposited in an alluvial fan and 

later cemented into rock.

fault. A break in rock characterized by displacement of one 

side relative to the other.

feldspar. A group of abundant silicate (silicon + oxygen) 

minerals, comprising more than 60% of Earth’s crust and 

occurring in all types of rocks. 

felsenmeer. From the German word meaning “sea of rocks”; 

a block field consisting of usually angular blocks with 

no fine sizes in the upper part, over solid or weathered 

bedrock, colluvium, or alluvium, without a cliff or ledge 

above as an apparent source. 

fine-grained. Describes sediment or sedimentary rock and 

texture in which the individual constituents are too small 

to distinguish with the unaided eye, specifically sediment 

or rock whose particles have an average diameter less 

than 1/16 mm (0.002 in), that is, silt-size particles and 

smaller. Also, describes a crystalline or glassy rock and 

texture in which the individual minerals are relatively 

small, specifically an igneous rock whose particles have an 

average diameter less than 1 mm (0.04 in). 

fissure. A fracture or crack in rock along which there is a 

distinct separation; commonly filled with mineral-bearing 

materials. 

fissure (volcanic). An elongated fracture or crack at the 

surface from which lava erupts.

fissure vent. A volcanic conduit having the form of a crack 

or fissure at Earth’s surface.

floodplain. The surface or strip of relatively smooth land 

composed of alluvium and adjacent to a river channel, 

constructed by the present river in its existing regimen 

and covered with water when the river overflows its 

banks. A river has one floodplain and may have one or 

more terraces representing abandoned floodplains.

fluvial. Of or pertaining to a river or rivers.

fold. A curve or bend in an originally flat structure, such 

as a rock stratum, bedding plane, or foliation; usually a 

product of deformation.

footwall. The lower wall of a fault. 

formation. Fundamental rock-stratigraphic unit that is 

mappable, lithologically distinct from adjoining strata, 

and has definable upper and lower contacts.

fossil. A remain, trace, or imprint of a plant or animal that 

has been preserved in the Earth’s crust since some past 

geologic time; loosely, any evidence of past life.

fracture. The breaking of a mineral other than along planes 

of cleavage. Also, any break in a rock such as a crack, joint, 

or fault.

freeze-thaw. The mechanical weathering process caused 

by alternate or repeated cycles of freezing and thawing 

water in pores, cracks, and other openings of rock and 

unconsolidated deposits, usually at the surface. 

friable. Describes a rock or mineral that is easily crumbled. 

frost action. The mechanical weathering process caused by 

alternate or repeated cycles of freezing and thawing of 

water in pores, cracks, and other openings, usually at the 

surface.

frost heaving. The uneven lifting or upward movement, and 

general distortion, of surface soils, rocks, vegetation, and 

structures such as pavements, due to subsurface freezing 

of water and growth of ice masses.

frost wedging. A type of mechanical disintegration, 

splitting, or breakup of a rock by which jointed rock is 

pried and dislodged by ice acting as a wedge.

fumarole. A vent, usually volcanic, from which gases and 

vapors are emitted. 

geology. The study of Earth, including its origin, history, 

physical processes, components, and morphology.

geomorphology. The study of the general configuration of 

surface landforms and their relationships to underlying 

structures, and of the history of geologic changes as 

recorded by these surface features.

geothermal. Pertaining to the heat of the interior of the 

Earth.

glassy. Describes the texture of certain extrusive igneous 

rocks that is similar to glass and developed as a 

result of rapid cooling of the lava, without distinctive 

crystallization. Synonymous with “vitreous.”

gradient. A degree of inclination (steepness of slope), or a 

rate of ascent or descent, of an inclined part of Earth’s 

surface with respect to the horizontal; expressed as a ratio 

(vertical to horizontal), a fraction (such as m/km or ft/

mi), a percentage (of horizontal distance), or an angle (in 

degrees).

graben. An elongated, downdropped trough or basin, 

bounded on both sides by high-angle normal faults that 

dip toward one another. 

granite. A coarse-grained, intrusive igneous rock in which 

quartz constitutes 10%–50% of the felsic (“light-colored”) 

components and the alkali feldspar/total feldspar ratio is 

generally restricted to the range of 65% to 90%; perhaps 

the best known of all igneous rocks.

gravel. An unconsolidated, natural accumulation of typically 

rounded rock fragments resulting from erosion; consists 

predominantly of particles larger than sand; that is, 

greater than 2 mm (1/12 in) across.

groundwater. That part of subsurface water that is in the 

zone of saturation, including underground streams.

hanging wall. The upper wall of a fault. 

hawaiite. An olivine-rich basalt. Also, a pale-green, ironpoor gem variety of olivine from the lavas of Hawaii.
56

hoodoo. A bizarrely shaped column, pinnacle, or pillar of 

rock, commonly produced in a region of sporadic heavy 

rainfall by differential weathering or erosion of horizontal 

strata, facilitated by layers of varying hardness and joints.

hornblende. A silicate (silicon + oxygen) mineral of sodium, 

potassium, calcium, magnesium, iron, and aluminum; 

commonly black and occurring in distinct crystals or in 

columnar, fibrous, or granular forms in hand specimens. 

The most common mineral of the amphibole group.

hot spring. A thermal spring whose temperature is above 

that of the human body.

hydrogeology. The science that deals with subsurface waters 

and related geologic aspects of surface waters, including 

the movement of groundwater; the mechanical, chemical, 

and thermal interaction of groundwater with the porous 

medium; and the transport of energy and chemical 

constituents by the flow of groundwater. Synonymous 

with “geohydrology.” 

hydrology. The study of liquid and solid water properties, 

circulation, and distribution, on and under the Earth’s 

surface and in the atmosphere.

hypersthene. A silicate (silicon + oxygen) mineral of the 

pyroxene group consisting of magnesium and iron.

iddingsite. A reddish-brown mixture of silicate (silicon 

+ oxygen) minerals, including iron, calcium, and 

magnesium, formed by the alteration of olivine; forms 

rust-colored patches in basic igneous rocks.

igneous. Describes a rock or mineral that solidified 

from molten or partly molten material; also, describes 

processes leading to, related to, or resulting from the 

formation of such rocks. One of the three main classes or 

rocks—igneous, metamorphic, and sedimentary.

ignimbrite. A pyroclastic flow deposit.

incision. Downward erosion by a stream, resulting in a 

deepened channel and commonly a narrow, steep-walled 

valley.

indurated. Describes a rock or soil hardened or 

consolidated by pressure, cementation, or heat.

induration. Hardening by heat, pressure, or the introduction 

of cementing material, especially the process by which 

relatively consolidated rock is made harder or more 

compact.

intermediate magma. Describes magma that contains 

between 62% and 63% silica and is moderately viscous, 

gas-rich, and sometimes erupts explosively, though it may 

also produce lava flows.

interstitial. Said of a mineral deposit in which the minerals 

fill the pores of the host rock.

intrusion. The process of emplacement of magma into 

preexisting rock. Also, the igneous rock mass formed. 

intrusive. Pertaining to intrusion, both the process and the 

rock body.

joint. A break in rock without relative movement of rocks on 

either side of the fracture surface.

lahar. A mixture of water and volcanic debris that moves 

rapidly down the slope of a volcano, characterized by a 

substantial component (>50%) of fine-grained material 

that acts as a matrix to give the deposit the strength it 

needs to carry the bigger clasts. 

laminated. Consisting of very thin compositional layers..

landslide. A collective term covering a wide variety of 

slope-movement landforms and processes that involve the 

downslope transport of soil and rock material en masse 

under the influence of gravity.

lapilli. Pyroclastic materials ranging between 2 and 64 mm 

(0.08 and 2.5 in) across with no characteristic shape; 

may be either solidified or still viscous upon landing. An 

individual fragment is called a lapillus.

lava. Molten or solidified magma that has been extruded 

though a vent onto Earth’s surface.

lava dome. A steep-sided mass of viscous, commonly 

blocky, lava extruded from a vent; typically has a rounded 

top and covers a roughly circular area; may be isolated or 

associated with lobes or flows of lava from the same vent; 

typically silicic (rhyolite or dacite) in composition.

lithify. To change to stone, or to petrify; especially to 

consolidate from a loose sediment to solid rock.

maar. A low-relief, broad volcanic crater formed by multiple 

shallow explosive eruptions. It is surrounded by a lowrelief rim of fragmental material, and may be filled by 

water.

magma. Molten rock beneath Earth’s surface capable of 

intrusion and extrusion. 

magmatism. The development and movement of magma, 

and its solidification as igneous rock. 

mantle. The zone of the Earth below the crust and above the 

core.

marker bed. A well-defined, easily identifiable stratum 

or body of strata that has sufficiently distinctive 

characteristics (such as lithology or fossil content) to 

facilitate correlation in field mapping or subsurface work. 

Also, a geologic formation that serves as a marker.

member. A lithostratigraphic unit with definable contacts; a 

subdivision of a formation.

mesa. A broad, flat-topped erosional hill or mountain with 

by steeply sloping sides or cliffs.

mineral. A naturally occurring inorganic crystalline solid 

with a definite chemical composition or compositional 

range.

monocline. A one-limbed fold in strata that are otherwise 

flat-lying.

mugearite. An extrusive or hypabyssal igneous rock of the 

alkali basalt suite containing oligoclase, alkali feldspar, and 

mafic minerals.

normal fault. A fault in which the hanging wall appears to 

have moved downward relative to the footwall; the angle 

of dip is usually 45°–90°. 

obsidian. A black or dark-colored volcanic glass, usually 

of rhyolite composition, characterized by conchoidal 

fracture.

olivine. A silicate (silicon + oxygen) mineral of magnesium 

and iron, (Mg,Fe)2

SiO4; commonly olive-green and an 

essential mineral in basalt, gabbro, and peridotite.

orogeny. A mountain-building event.

outcrop. Any part of a rock mass or formation that is 

exposed or “crops out” at Earth’s surface. 
57

oxide. A mineral group composed of oxygen plus an element 

or elements, for example, iron in hematite, Fe2

O3; or 

aluminum in corundum, Al2

O3.

palagonite. An altered volcanic, specifically basaltic, glass 

that becomes pillow lava or occurs in amygdules.

palagonite tuff. A pyroclastic rock consisting of angular 

fragments of hydrothermally altered or weathered 

palagonite, produced by explosive interaction of mafic 

magma and water.

paleotopography. The topographic relief of an area at a 

particular time in the geologic past.

patterned ground. Well-defined, more or less symmetrical 

forms such as circles, polygons, nets, steps, and stripes in 

surficial material that develop as a result of intense frost 

action.

pebble. A small rounded rock, especially a waterworn stone, 

between 4 and 64 mm (0.16 and 2.5 in) across.

period. The fundamental unit of the worldwide geologic 

time scale. It is lower in rank than era and higher than 

epoch. The geochronologic unit during which the rocks of 

the corresponding system were formed.

permeability. A measure of the relative ease with which 

a fluid moves through the pore spaces of a rock or 

unconsolidated deposit.

phenocryst. A coarse-grained crystal in a porphyritic 

igneous rock.

phreatomagmic. A term encompassing all volcanic activity 

that results from the interaction between lava, magmatic 

heat, or gases and water at or near the surface of the 

Earth. Synonymous with “hydrovolcanic.”

piedmont. A gently sloping area at the base of a mountain 

front. Synonymous with “bajada.” Also, describes a 

feature (e.g., plain, slope, or glacier) that lies or formed at 

the base of a mountain or mountain range.

pillow lava. A general term for lavas displaying pillow 

structures and considered to have formed in a subaqueous 

environment; such lava is usually basaltic or andesitic.

pillow structure. A structure observed in certain extrusive 

igneous rocks that is characterized by discontinuous bunshaped masses ranging in size from a few centimeters to a 

meter or more in greatest dimension. They are considered 

to be the result of subaqueous extrusion.

plagioclase. A silicate (silicon + oxygen) mineral of the 

feldspar group that contains both sodium and calcium 

ions that freely substitute for one another; characterized 

by striations (parallel lines) in hand specimens. 

planar. Lying or arranged as a plane or in planes, usually 

implying more or less parallelism, as in bedding or 

cleavage.

plateau. A broad, flat-topped topographic high (terrestrial 

or marine) of great extent and elevation above the 

surrounding plains, canyons, or valleys.

Plinian eruption. An explosive eruption characterized by 

large amounts of tephra and a tall eruption column from 

which a steady, turbulent stream of fragmented magma 

and magmatic gas is released at a high velocity.

porosity. The percentage of total void space in a volume of 

rock or unconsolidated deposit.

porphyritic. Describes an igneous rock of any composition 

that contains conspicuous phenocrysts (larger crystals) in 

a fine-grained groundmass.

porphyry. An igneous rock consisting of abundant coarsegrained crystals in a fine-grained groundmass.

potassium feldspar. A feldspar mineral rich in potassium 

such as orthoclase, microcline, and sanidine.

Precambrian. A commonly used term to designate all rocks 

older than the Cambrian Period of the Standard Global 

Chronostratigraphic Scale. It includes the Archean and 

Proterozoic eons and represents 90% of geologic time.

pumice. A highly vesicular pyroclast with very low bulk 

density and thin vesicle walls.

pumiceous. Describes a texture of volcanic rock consisting 

of tiny gas holes such as in pumice; finer than scoriaceous.

pyroclast. An individual particle ejected during a volcanic 

eruption; usually classified according to size.

pyroclastic. Describes clastic rock material formed by 

volcanic explosion or aerial expulsion from a vent; also, 

describes a rock texture of explosive origin. It is not 

synonymous with “volcanic.”

pyroclastic flow. A hot, typically >800°C (1,500°F), chaotic 

mixture of rock fragments, gas, and ash that travels rapidly 

(tens of meters per second) away from a volcanic vent or 

collapsing flow front.

pyroclastic surge. Low-density, dilute, turbulent pyroclastic 

flow. The deposits may be thinly bedded, laminated, and 

cross-bedded.

pyroxene. A group of silicate (silicon + oxygen) minerals 

composed of magnesium and iron with the general 

formula (Mg,Fe)SiO3; characterized by short, stout 

crystals in hand specimens. 

quartz. Silicon dioxide, SiO2. The only silicate (silicon + 

oxygen) mineral consisting entirely of silicon and oxygen. 

Synonymous with “crystalline silica.”

quartzite. Metamorphosed quartz sandstone. A mediumgrained, nonfoliated metamorphic rock composed mostly 

of quartz.

radiocarbon age. An isotopic age expressed in years and 

calculated from the quantitative determination of the 

amount of carbon-14 remaining in an organic material. 

Synonymous with “carbon-14 age.”

red bed. Sedimentary strata that is predominantly red due 

to the presence of ferric iron oxide (hematite) coating 

individual grains; usually sandstone, siltstone, or shale.

relict. Describes a topographic feature that remains after 

other parts of the feature have been removed or have 

disappeared, for example, a “relict beach ridge” or a 

“relict hill.” Also, a landform made by processes no longer 

operative such as glaciated forms in the northern United 

States or sand dunes in rain forests.

reservoir. An artificial or natural storage place for water, 

such as a lake, pond, or aquifer, from which the water may 

be withdrawn for such purposes as irrigation, municipal 

water supply, or flood control.

resurgent caldera. A caldera in which the downdropped 

block is uplifted by magmatic intrusion following crater 

formation.
58

resurgent cauldron. A cauldron in which the cauldron block, 

following subsidence, has been uplifted, usually in the 

form of a structural dome.

rhyodacite. A volcanic rock that contains approximately 

68%–72% silica and is intermediate in composition 

between rhyolite and dacite.

rhyolite. A volcanic rock that is characteristically light in 

color, contains approximately 72% or more of silica, and 

is rich in potassium and sodium. 

rift. A region of Earth’s crust where extension results in 

formation of many related normal faults, commonly 

associated with volcanic activity.

rift valley. A depression formed by grabens along the crest 

of a mid-ocean ridge or in a continental rift zone.

rock. An aggregate of one or more minerals (e.g., granite), a 

body of undifferentiated mineral matter (e.g., obsidian), 

or a body of solid organic material (e.g., coal).

rockfall. The most rapid type of slope movement in which a 

newly detached fragment of bedrock of any size falls from 

a cliff or other very steep slope, traveling straight down or 

in a series of leaps and bounds down a slope.

rock glacier. A mass of poorly sorted angular boulders and 

fine material, with interstitial ice a meter or so below the 

surface (ice-cemented) or containing a buried ice glacier 

(ice-cored).

sand. A clastic particle smaller than a granule and larger than 

a silt grain, with a diameter ranging from 1/16 to 2 mm 

(0.0025 to 0.08 in).

sandstone. Clastic sedimentary rock composed of 

predominantly sand-sized grains.

scarp. A steep cliff or topographic step resulting from 

displacement on a fault or as a result of slope movement 

or erosion. Synonymous with “escarpment.”

scoria. A bomb-size pyroclast that is irregular in form and 

generally very vesicular.

sediment. An eroded and deposited, unconsolidated 

accumulation of rock and mineral fragments.

sedimentary. Pertaining to or containing sediment. 

sedimentary rock. A rock resulting from the consolidation 

of loose sediment that has accumulated in layers; it may 

be “clastic,” consisting of mechanically formed fragments 

of older rock; “chemical,” formed by precipitation from 

solution; or “organic,” consisting of the remains of plants 

and animals. One of the three main classes of rock—

igneous, metamorphic, and sedimentary. 

sedimentation. The process of forming or accumulating 

sediment into layers, including the separation of rock 

particles from parent rock, the transportation of these 

particles to the site of deposition, the actual deposition or 

settling of the particles, the chemical and other changes 

occurring in the sediment, and the ultimate consolidation 

of the sediment into solid rock. 

seismic. Pertaining to an earthquake or Earth vibration, 

including those that are artificially induced.

seismicity. The phenomenon of movements in the Earth’s 

crust. Synonymous with “seismic activity.”

sequence. A succession of geologic events, processes, or 

rocks, arranged in chronologic order to show their relative 

position and age with respect to geologic history as a 

whole. Also, a rock-stratigraphic unit that is traceable 

over large areas and defined by sediment associated with a 

major sea level transgression–regression.

sheet erosion. The removal of thin layers of surface material 

more or less evenly from an extensive area of gently 

sloping land by broad continuous sheets of running water, 

rather than by streams flowing in well-defined channels.

sheet flow. The downslope movement or overland 

flow of water, in the form of a thin, continuous film, 

over relatively smooth soil or rock surfaces and not 

concentrated into channels larger than rills.

sheetwash. A sheetflood occurring in a humid region. Also, 

the material transported and deposited by the water of a 

sheetwash. Used as a synonym of “sheet flow” and “sheet 

erosion.”

shield volcano. A broad shield-shaped volcano that is built 

up by successive, mostly effusive, eruptions of low-silica 

lava.

sierra. A high range of hills or mountains, especially one 

having jagged or irregular peaks that resemble the teeth of 

a saw.

silica. Silicon dioxide, SiO2, an essential constituent of many 

minerals, occurring as crystalline quartz, cryptocrystalline 

chalcedony, and amorphous opal.

siliceous. Describes a rock or other substance containing 

abundant silica.

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay, 0.0039 to 

0.063 mm (0.00015 to 0.0025 in) across.

silting. The accumulation of silt suspended throughout a 

body of standing water or in some considerable portion 

of it. In particular, the choking, filling, or covering 

with stream-deposited silt behind a dam or other place 

of retarded flow, or in a reservoir. Synonymous with 

“siltation.”

slope. The inclined surface of any part of Earth’s surface, 

such as a hillslope. Also, a broad part of a continent 

descending into an ocean.

slope movement. The gradual or rapid downslope 

movement of soil or rock under gravitational stress. 

Synonymous with “mass wasting.”

slope wash. Soil and rock material that is or has been 

transported down a slope under the force of gravity and 

assisted by running water not confined to channels; also, 

the process by which slope-wash material is moved.

slump. A generally large, coherent slope movement with a 

concave failure surface and subsequent backward rotation 

relative to the slope.

soil. The unconsolidated portion of the Earth’s crust 

modified through physical, chemical, and biotic processes 

into a medium capable of supporting plant growth.

spalling. The process by which scales, plates, or flakes of 

rock, from less than a centimeter to several meters thick, 

successively fall from the bare surface of a large rock mass; 

a form of exfoliation.
59

spatter. An accumulation of initially very fluid pyroclasts, 

usually stuck together, coating the surface around a vent.

spring. A place where groundwater flows naturally from a 

rock or the soil onto the land surface or into a body of 

surface water. 

strata. Tabular or sheetlike layers of sedimentary rock 

that are visually distinctive from other layers above and 

below. The singular form of the term is stratum, but is less 

commonly used.

stratigraphy. The geologic study of the origin, occurrence, 

distribution, classification, correlation, and age of rock 

layers, especially sedimentary rocks.

stream. Any body of water moving under gravity flow in a 

clearly confined channel.

stream channel. A long, narrow depression shaped by the 

concentrated flow of stream water.

stream terrace. A planar surface alongside a stream valley 

representing the remnants of an abandoned floodplain, 

stream bed, or valley floor produced during a former stage 

of erosion or deposition.

strike. The compass direction of the line of intersection of 

an inclined surface with a horizontal plane.

strike-slip fault. A fault with measurable offset where the 

relative movement is parallel to the strike of the fault. 

Described as left-lateral (sinistral) when relative motion of 

the block opposite the observer is to the left, and rightlateral (dextral) when relative motion is to the right. 

structural geology. The branch of geology that deals with 

the description, representation, and analysis of structures, 

primarily on a moderate to small scale. The subject is 

similar to tectonics, but the latter term is generally used 

for the analysis of broader regional or historical phases.

structure. The attitudes and relative positions of the rock 

masses of an area resulting from such processes as 

faulting, folding, and igneous intrusion.

talus. Rock fragments, usually coarse and angular, lying at 

the base of a cliff or steep slope from which they have 

fallen.

tectonic. Describes a feature or process related to large-scale 

movement and deformation of Earth’s crust.

tectonics. The geologic study of the broad structural 

architecture and deformational processes of the 

lithosphere and asthenosphere.

tephra. A collective term used for all pyroclastic material, 

regardless of size, shape, or origin, ejected into the air 

during a volcanic eruption.

terrace. Any long, narrow, relatively level or gently inclined 

surface (i.e., a bench or steplike ledge) that is bounded 

along one edge by a steeper descending slope and along 

the other edge by a steeper ascending slope, thus breaking 

the continuity of the slope; commonly occurs along the 

margin and above the level of a body of water, marking a 

former water level.

topography. The general morphology of Earth’s surface, 

including relief and locations of natural and human-made 

features.

trace (structural geology). The intersection of a geological 

surface with another surface, for example, the trace 

of bedding on a fault surface, or the trace of a fault or 

outcrop on the ground.

trace fossil. A fossilized feature such as a track, trail, 

burrow, or coprolite (dung), that preserves evidence of an 

organism’s life activities, rather than the organism itself. 

Compare to “body fossil.”

transverse. Said of an entity that is extended in a crosswise 

direction, especially of a topographic feature that is 

oriented at right angles to the grain or general strike of a 

region.

trend. The direction or bearing of an outcrop of a geologic 

feature such as an ore body, fold, or orogenic belt.

tuff. Consolidated or cemented volcanic ash and lapilli.

tuffaceous. Describes non-volcanic, clastic sediments that 

contain ash-size pyroclasts.

type locality. The place where a geologic feature such as an 

ore occurrence, a particular kind of igneous rock, or the 

type specimen of a fossil species was first recognized and 

described.

unconformable. Describes strata that do not succeed the 

underlying rocks in immediate order of age or in parallel 

position, especially younger strata that do not have 

the same dip and strike as the underlying rocks. Also, 

describes the contact between unconformable rocks.

unconformability. The quality, state, or condition of 

being unconformable, such as the relationship of 

unconformable strata.

unconformity. A substantial break or gap in the geologic 

record where a rock unit is overlain by another that is not 

next in stratigraphic succession, resulting from either a 

change that caused deposition to cease for a considerable 

span of time or erosion with loss of the previously formed 

record.

undercutting. The removal of material at the base of a steep 

slope by the erosive action of water (such as a meandering 

stream), sand-laden wind in a desert, or waves along a 

coast.

uplift. A structurally high area in Earth’s crust produced by 

movement that raises the rocks.

vadose. Refers to the unsaturated zone between the land 

surface and the water table that includes air, gases, and 

water held by capillary action.

vent. Any opening at Earth’s surface through which magma 

erupts or volcanic gases are emitted.

vesicle. A cavity of variable shape formed by the entrapment 

of a gas bubble during solidification of lava.

vesicular. Describes the texture of a rock, especially lava, 

characterized by abundant vesicles formed as a result of 

the expansion of gases during the fluid stage of a lava.

viscosity. The property of a substance to offer internal 

resistance to flow.

volatile. Readily vaporizable.

volatile component. Material in magma, such as water or 

carbon dioxide, whose vapor pressures is sufficiently high 

to be concentrated as a gas.
60

volcanic. Pertaining to the activities, structures, or rock types 

of a volcano. A synonym of extrusive.

volcaniclastic. Pertaining to all clastic volcanic materials 

formed by any process of fragmentation, dispersed by any 

kind of transporting agent, deposited in any environment, 

or mixed in any significant portion with nonvolcanic 

fragments.

volcanogenic. Formed by processes directly connected with 

volcanism.

volcanism. The processes by which magma and its 

associated gases rise into Earth’s crust and are extruded 

onto the surface and into the atmosphere.

water table. The surface between the saturated zone and the 

unsaturated zone. Synonymous with “groundwater table” 

and “water level.”

weathering. The physical, chemical, and biological 

processes by which rock is broken down, particularly at 

Earth’s surface.

welded tuff. A glass-rich pyroclastic rock that has been 

indurated by the welding together of its glass shards under 

the combined action of the heat retained by particles, the 

weight of overlying material, and hot gases. 

welding. Consolidation of sediments under pressure. Also, 

the diagenetic process whereby discrete crystals and/or 

grains become attached to each other during compaction 

Wisconsinan. Pertaining to the classical fourth glacial stage 

of the Pleistocene Epoch in North America, following 

the Sangamonian interglacial stage and preceding the 

Holocene Epoch.

xenocryst. A crystal that resembles a phenocryst in igneous 

rock but is foreign to the body of rock in which it occurs.

zeolite. A group of silicate (silicon + oxygen) minerals that 

commonly occur as well-formed crystals in the cavities of 

mafic igneous rocks, particularly basalt. 
61

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Additional References

This chapter lists additional references, resources, and websites that may be of use to resource 

managers. Web addresses are valid as of August 2015. Refer to Appendix B for laws, regulations, and 

policies that apply to NPS geologic resources.

Geology of National Park Service Areas

● NPS Geologic Resources Division

Energy and Minerals; Active Processes and Hazards; 

Geologic Heritage:

http://nature.nps.gov/geology/

● NPS Geologic Resources Inventory: http://www.

nature.nps.gov/geology/inventory/index.cfm

● NPS Geoscientist-In-the-Parks (GIP) internship 

and guest scientist program:

http://www.nature.nps.gov/geology/gip/index.cfm

● NPS Views program (geology-themed modules are 

available for Geologic Time, Paleontology, Glaciers, 

Caves and Karst, Coastal Geology, Volcanoes, and a 

variety of geologic parks):

http://www.nature.nps.gov/views/

● USGS Geology of National Parks (including 3D 

imagery): http://3dparks.wr.usgs.gov/

NPS Resource Management Guidance and 

Documents

● Management Policies 2006 (Chapter 4: Natural 

resource management):

http://www.nps.gov/policy/mp/policies.html

● 1998 National parks omnibus management act: 

http://www.gpo.gov/fdsys/pkg/PLAW-105publ391/

pdf/PLAW-105publ391.pdf

● NPS-75: Natural resource inventory and 

monitoring guideline:

http://www.nature.nps.gov/nps75/nps75.pdf

● NPS Natural resource management reference 

manual #77: http://www.nature.nps.gov/Rm77/

● Geologic monitoring manual (Young, R., and 

L. Norby, editors. 2009. Geological monitoring. 

Geological Society of America, Boulder, Colorado): 

http://nature.nps.gov/geology/monitoring/index.

cfm

● NPS Technical Information Center (TIC) (Denver, 

Colorado; repository for technical documents): 

http://www.nps.gov/dsc/technicalinfocenter.htm

Climate Change Resources

● NPS Climate Change Response Program Resources: 

http://www.nps.gov/subjects/climatechange/

resources.htm

● US Global Change Research Program:

http://globalchange.gov/home

● Intergovernmental Panel on Climate Change:

http://www.ipcc.ch/

Geological Surveys and Societies

● New Mexico Bureau of Geology and Mineral 

Resources: http://geoinfo.nmt.edu/

● US Geological Survey: http://www.usgs.gov/

● Geological Society of America:

http://www.geosociety.org/

● American Geophysical Union: http://sites.agu.org/

● American Geosciences Institute:

http://www.americangeosciences.org/

● Association of American State Geologists:

http://www.stategeologists.org/

US Geological Survey Reference Tools

● National geologic map database (NGMDB):

http://ngmdb.usgs.gov/

● Geologic names lexicon (GEOLEX; geologic unit 

nomenclature and summary):

http://ngmdb.usgs.gov/Geolex/geolex_home.html

● Geographic names information system (GNIS; 

official listing of place names and geographic 

features): http://gnis.usgs.gov/

● GeoPDFs (download searchable PDFs of any 

topographic map in the United States):

http://store.usgs.gov (click on “Map Locator”)

● Publications warehouse (many publications 

available online): http://pubs.er.usgs.gov

● Tapestry of time and terrain (descriptions of 

physiographic provinces):

http://tapestry.usgs.gov/Default.html

73

Appendix A: Scoping Participants

The following people attended the GRI scoping meeting for Bandelier National Monument, held on 13–

14 July 2005, or the follow-up report writing conference call, held on 3 July 2014. Discussions during 

these meetings supplied a foundation for this GRI report. The scoping summary document is available 

on the GRI publications website: http://go.nps.gov/gripubs.

2005 Scoping Meeting Participants

Name Affiliation Position

Kay Beeley Bandelier National Monument Cartographic Technician

Doug Bland New Mexico Bureau of Geology and Mineral Resources Geologist / Special Projects Manager

Tim Connors NPS Geologic Resources Division Geologist

Nelia Dunbar New Mexico Bureau of Geology and Mineral Resources Geochemist

Fraser Goff New Mexico Bureau of Geology and Mineral Resources Volcanologist

Bruce Heise NPS Geologic Resources Division Geologist

Brian Jacobs Bandelier National Monument Natural Resources Manager

Elaine Jacobs Colorado State University Geologist

Katie KellerLynn Colorado State University Geologist / Research Associate

Shari Kelley New Mexico Bureau of Geology and Mineral Resources Geophysicist / Field Geologist

Ifer McCollom NPS Geologic Resources Division GIS Specialist

Lauren Meyer Bandelier National Monument Vanishing Treasures Program, Architectural 

Conservator

Greer Price New Mexico Bureau of Geology and Mineral Resources Senior Geologist / Chief Editor

Peter Scholle New Mexico Bureau of Geology and Mineral Resources Director / State Geologist

Mike Timmons New Mexico Bureau of Geology and Mineral Resources Geologic Mapping Program Manager

Stacy Wagner New Mexico Bureau of Geology and Mineral Resources Senior Geologic Research Associate

2014 Conference Call Participants

Name Affiliation Position

Kay Beeley Bandelier National Monument Cartographic Technician

Tom Betts Bandelier National Monument Chief Ranger

Eric Bilderback NPS Geologic Resources Division Geologic Hazards and Disturbed Lands Program 

Lead

Tim Connors NPS Geologic Resources Division Geologist / GRI Maps Coordinator

Brian Jacobs Bandelier National Monument Natural Resources Manager

Barbara Judy Bandelier National Monument Chief of Resource Management

Katie KellerLynn Colorado State University Geologist / Research Associate

Shari Kelley New Mexico Bureau of Geology and Mineral Resources Geophysicist / Field Geologist

Jason Kenworthy NPS Geologic Resources Division Geologist / GRI Reports Coordinator

Jason Lott Bandelier National Monument Superintendent

Stephen Monroe NPS Southern Colorado Plateau Network Hydrologist

Hal Pranger NPS Geologic Resources Division Geologic Features and Systems Branch Chief

Dale Coker Bandelier National Monument Trails Program

Joseph Gurule Bandelier National Monument Facilities Manager

75

Appendix B: Geologic Resource Laws, Regulations, and Policies

The NPS Geologic Resources Division developed this table to summarize laws, regulations, and policies 

that specifically apply to National Park Service minerals and geologic resources. The table does not 

include laws of general application (e.g., Endangered Species Act, Clean Water Act, Wilderness Act, 

National Environmental Policy Act, or National Historic Preservation Act). The table does include the 

NPS Organic Act when it serves as the main authority for protection of a particular resource or when 

other, more specific laws are not available. Information is current as of August 2015. Contact the NPS 

Geologic Resources Division for detailed guidance.

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Paleontology

National Parks Omnibus Management 

Act of 1998, 16 USC § 5937 protects the 

confidentiality of the nature and specific 

location of paleontological resources and 

objects.

Paleontological Resources Preservation 

Act of 2009, 16 USC § 470aaa et 

seq. provides for the management and 

protection of paleontological resources on 

federal lands.

36 CFR § 2.1(a)(1)(iii) prohibits destroying, 

injuring, defacing, removing, digging or 

disturbing paleontological specimens or 

parts thereof.

Regulations in association with 2009 PRPA 

are being finalized (August 2015).

Section 4.8.2 requires NPS to protect 

geologic features from adverse effects of 

human activity.

Section 4.8.2.1 emphasizes Inventory and 

Monitoring, encourages scientific research, 

directs parks to maintain confidentiality of 

paleontological information, and allows 

parks to buy fossils only in accordance with 

certain criteria.

Rocks and 

Minerals

NPS Organic Act, 16 USC § 1 et seq.

directs the NPS to conserve all resources 

in parks (including rock and mineral 

resources), unless otherwise authorized by 

law.

36 CFR § 2.1 prohibits possessing, 

destroying, disturbing mineral resources...

in park units.

Section 4.8.2 requires NPS to protect 

geologic features from adverse effects of 

human activity.

Park Use of Sand and Gravel

Materials Act of 1947, 30 USC § 601

does not authorize the NPS to dispose of 

mineral materials outside of park units.

None applicable.

Section 9.1.3.3 clarifies that only the 

NPS or its agent can extract park-owned 

common variety minerals (e.g., sand and 

gravel), and:

-only for park administrative uses;

-after compliance with NEPA and other 

federal, state, and local laws, and a 

finding of non-impairment;

-after finding the use is park’s most 

reasonable alternative based on 

environment and economics;

-parks should use existing pits and create 

new pits only in accordance with parkwide borrow management plan;

-spoil areas must comply with Part 6 

standards; and

-NPS must evaluate use of external 

quarries.

Any deviation from this policy requires a 

written waiver from the Secretary, Assistant 

Secretary, or Director.
76

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Upland and Fluvial Processes

Rivers and Harbors Appropriation 

Act of 1899, 33 USC § 403 prohibits the 

construction of any obstruction on the 

waters of the United States not authorized 

by congress or approved by the USACE.

Clean Water Act 33 USC § 1342 requires 

a permit from the USACE prior to any 

discharge of dredged or fill material 

into navigable waters (waters of the US 

[including streams]). 

Executive Order 11988 requires federal 

agencies to avoid adverse impacts to 

floodplains. (see also D.O. 77-2)

Executive Order 11990 requires plans for 

potentially affected wetlands (including 

riparian wetlands). (see also D.O. 77-1)

None applicable.

Section 4.1 requires NPS to manage 

natural resources to preserve fundamental 

physical and biological processes, as well 

as individual species, features, and plant 

and animal communities; maintain all 

components and processes of naturally 

evolving park ecosystems.

Section 4.1.5 directs the NPS to reestablish natural functions and processes 

in human-disturbed components of natural 

systems in parks, unless directed otherwise 

by Congress.

Section 4.4.2.4 directs the NPS to allow 

natural recovery of landscapes disturbed by 

natural phenomena, unless manipulation of 

the landscape is necessary to protect park 

development or human safety. 

Section 4.6.4 directs the NPS to (1) 

manage for the preservation of floodplain 

values; [and] (2) minimize potentially 

hazardous conditions associated with 

flooding.

Section 4.6.6 directs the NPS to manage 

watersheds as complete hydrologic systems 

and minimize human-caused disturbance 

to the natural upland processes that deliver 

water, sediment, and woody debris to 

streams.

Section 4.8.1 directs the NPS to allow 

natural geologic processes to proceed 

unimpeded. Geologic processes...include...

erosion and sedimentation...processes. 

Section 4.8.2 directs the NPS to protect 

geologic features from the unacceptable 

impacts of human activity while allowing 

natural processes to continue.

Caves and Karst Systems

Federal Cave Resources Protection Act 

of 1988, 16 USC §§ 4301 – 4309 requires 

Interior/Agriculture to identify “significant 

caves” on Federal lands, regulate/

restrict use of those caves as appropriate, 

and include significant caves in land 

management planning efforts. Imposes 

civil and criminal penalties for harming 

a cave or cave resources. Authorizes 

Secretaries to withhold information about 

specific location of a significant cave from 

a Freedom of Information Act (FOIA) 

requester. 

National Parks Omnibus Management 

Act of 1998, 16 USC § 5937 protects the 

confidentiality of the nature and specific 

location of cave and karst resources.

36 CFR § 2.1 prohibits possessing/ 

destroying/disturbing...cave resources...in 

park units.

43 CFR Part 37 states that all NPS caves 

are “significant” and sets forth procedures 

for determining/releasing confidential 

information about specific cave locations to 

a FOIA requester.

Section 4.8.1.2 requires NPS to maintain 

karst integrity, minimize impacts.

Section 4.8.2 requires NPS to protect 

geologic features from adverse effects of 

human activity.

Section 4.8.2.2 requires NPS to protect 

caves, allow new development in or on 

caves if it will not impact cave environment, 

and to remove existing developments if 

they impair caves.

Section 6.3.11.2 explains how to manage 

caves in/adjacent to wilderness.
77

Resource Resource-specific Laws Resource-specific Regulations 2006 Management Policies Geothermal

Geothermal Steam Act of 1970, 30 USC 

§ 1001 et seq. as amended in 1988, 

states that

-no geothermal leasing is allowed in parks;

-“significant” thermal features exist in 16 

park units (features listed by the NPS at 52 

Fed. Reg. 28793-28800 [August 3, 1987], 

and thermal features in Crater Lake, Big 

Bend, and Lake Mead);

-NPS is required to monitor those features; 

and

-based on scientific evidence, Secretary 

of Interior must protect significant NPS 

thermal features from leasing effects.

Geothermal Steam Act Amendments 

of 1988, Public Law 100--443 prohibits 

geothermal leasing in the Island Park 

known geothermal resource area near 

Yellowstone and outside 16 designated 

NPS units if subsequent geothermal 

development would significantly adversely 

affect identified thermal features. 

None applicable

Section 4.8.2.3 requires NPS to

-preserve/maintain integrity of all thermal 

resources in parks.

-work closely with outside agencies, and

-monitor significant thermal features.

Soils

Soil and Water Resources Conservation 

Act, 16 USC §§ 2011–2009 provides for 

the collection and analysis of soil and 

related resource data and the appraisal of 

the status, condition, and trends for these 

resources.

Farmland Protection Policy Act, 7 USC 

§ 4201 et. seq. requires NPS to identify 

and take into account the adverse effects 

of Federal programs on the preservation 

of farmland; consider alternative actions, 

and assure that such Federal programs 

are compatible with State, unit of local 

government, and private programs 

and policies to protect farmland. NPS 

actions are subject to the FPPA if they 

may irreversibly convert farmland (directly 

or indirectly) to nonagricultural use and 

are completed by a Federal agency or 

with assistance from a Federal agency. 

Applicable projects require coordination 

with the Department of Agriculture’s 

Natural Resources Conservation Service 

(NRCS).

7 CFR Parts 610 and 611 are the US 

Department of Agriculture regulations 

for the Natural Resources Conservation 

Service. Part 610 governs the NRCS 

technical assistance program, soil erosion 

predictions, and the conservation of private 

grazing land. Part 611 governs soil surveys 

and cartographic operations. The NRCS 

works with the NPS through cooperative 

arrangements.

Section 4.8.2.4 requires NPS to

-prevent unnatural erosion, removal, and 

contamination;

-conduct soil surveys;

-minimize unavoidable excavation; and

-develop/follow written prescriptions 

(instructions).

The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and 

other information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated 

Island Communities.

NPS 315/129825, September 2015
National Park Service

U.S. Department of the Interior

Natural Resource Stewardship and Science 

1201 Oak Ridge Drive, Suite 150 

Fort Collins, Colorado 80525

www.nature.nps.gov

EXPERIENCE YOUR AMERICATM
\ 

' I 

D 2 

This map was produced by James Winter and Georgia Hybels (Colorado State 

Univ"""Y) In September, 2015. It is an C>/eMeW or compiled geolog

ic data 

p-red as part of lhe NPS Geologic Resources lnventoiy. This map is not• 

substitute for sit~spedfic investigations. 

The ""'":e maps used in creallon ol lhe digital geologic data product Include 

New Mexlco Bureau of Geology and Minoral Res<>urces and U.S. Geological 

Surwy l'Ub

licalions (see Geologic Map Data chapter for specific sources). 

As per source map scale and U.S. Nallonal Map Accuracy Standards, geologic features represented here are within 12 m (40ft)(1:24,000 scale data) or 25 m 

(83 ft) (I 

:SQ,000 scale data) of their true location. 

AD digital geologic data and publications prepared as pan of the Geologic 

Resoun:es Inventory are available, at the NPS Integrated Resource Management 

Applications Portal (IRMA), httpsthnma.nps.gov/App/Relerenc:e.'Search. Enter 

"GR.I'" as thesearch text and select a patk fmtn the unit list. 

,, fumarole 

• p:itlloflmetit 

majO(payed roads 

--.....u - .... - • tandsl~dirKdot\.ktlCPM'lor~nain 

-­1.w\dsl~escar~.~ort.tn.ain 

Folds 

tl'Ol"IOCl~.known«otrtain 

F.ults 

_L ncm.at fault. tro.<m0t c:enan. Bat andb.!11 on d:),,,.mtwown blc:d-: 

--· ncnnaa fault. appro«lrnate 

-­ naYnat fault, concYed 

___,__. ncnna 1-.ilt, queried 

--­ tlCWTl\allault,~.wlqUl!tifd 

- - - - ncm.at fault, intetttd

-Line­­ash bed. kN:lwn«cenlitl 

--+ flew dlrecuonh, troNnor Cl'rtaln 

Otherl.lnefNtuNI q"""a,,glebo,,.,tvy 

Geol09k Units 

,UJy\jn,(Holocene 10 Ple..!ooetW) 

AIII.MalfM~ltS~neiotnidtlePlelsl~) 

AlkMal bedsaf sand (Holcxtntto Lue Aeistocet'lt) 

Allwlal and darl dfposlt(HolOOl!tle toFleisto<:ene} 

Landsa'.te$ (HolcX.tf'lt t0PleiStocene) 

T«tactg~~ION!IS~ 

Boulder llelds O,lolocene to Pletmcene) 

ffedMOM a8'.Mal dtposlt. grayel, sand and Siry sand ~ePl@ISb)(tnti 

Vallesllh)'Ollte, EIC-Pyn)dastlc&eds(~) 

cerro 

_,_) TOiedo formation, Valle bledo Member. Old Rabbtt Motl'ltaln ck>brts-fbN

cem:i TdecbFormatiOn, va~Toledo~.Rabbit Moi.a'lsaln ffiyoliire (Pie!~~) 

eet,obledo FOtma?lon, Vale lOl!do (Pleisaoctnt) 

Pledtnont alltMal ~t.poo,ty10l'ledgr-.Mland sand Ctl*ldle Pitka~) 

AlkMAI depoisa:, ootible ar.d boulder gtiMI(mldcle? flei!.rocene) 

Pledtrwont all!Mal depo5tt, g,;wel. lilt and~sand (tri:lcle? Aelstooent) 

&earl'Hd Rh)<ollte, Fetalla Tutr Membet (MIO(ent} 

sa,n~ G'°'C>, i#ldMded (MIOt'.:eN:) 

lSIY \tllr.anidaistk~ts(MlocetletoUfll)ef'Olgo(ent} 

'91:¥ ChattlU.Forma!JOn, IOWH VallltoM«nber !,Mloctnt) 

1ilb R!SUqueFcmlatlor\ basalt flow(MIOcene toUA)efOI~ 

1$(1( Te11uqut Fol"tNtiOI\ CNtl'la-EI Rito M.!trbef(MIOeent) 

?;lb Basalt flo,ysa,d CW!dets(late MiXenel 

- PaliuCar,pif.otma'liOn, ~M'ldeslre,undvtded(MIOO!tlt) - PaRucain,,on Fc:w't'Ntlor\. po,p~dadt.e ttA'i CMIOcentJ - P.alluCat1)'0l'IEom\Mi)l\porpl'fp11i:andeSl,t(MiOCet1t) 

Paliz.a CanyonFol'rnaliOt\. porpl¥'fdc hotrtJiende dadie(M~) 

C.anov.as Clf¥l"I Rtl)dte(MIOcetle) 
Map Unit Properties Table: Bandelier National Monument, Page 1 of 11

Map Unit Properties Table: Bandelier National Monument 

These 54 units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez 

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type. 

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY 

(Holocene to Pleistocene)

Alluvium

(Qal)

River-deposited gravel, sand, and silt in modern drainages. 

Beds generally less than 0.5 m (2 ft) thick, with maximum 

thickness exceeding 15 m (50 ft). 

Rio Grande Rift—modern alluvium is not considered part 

of the Santa Fe Group.

Paleontological Resources—in situ fossils (e.g., charcoal) 

occur in Holocene deposits in Frijoles Canyon. Ages range 

from 2,230 ± 250 to 4,160 ± 40 radiocarbon years before 

present (BP), or 1,929–2,496 to 4,152–4,297 calendar 

years BP (as computed using Stuiver et al. 2015).

Fires, Fluvial Geomorphology, and Slope 

Movements—Qal includes sediment transported during 

post-fire flooding. Also includes gravel in stream channels, 

which if removed during post-fire flooding may induce 

rapid stream incision.

Landscape Evolution—primarily represents modern-day 

alluvium in present-day stream channels but may be as old 

as El Cajete pyroclastic beds (Qvec; 60,000–50,000 years 

ago).

QUATERNARY 

(Holocene to Pleistocene)

Alluvial fan deposits

(Qfa) 

Coarse to fine river-deposited gravel and sand, silt, and 

clay; some fan deposits are difficult to distinguish from 

older alluvial fans. Thickness 2–20 m (7–70 ft). 

El Cajete Pyroclastic Beds—Qfa includes some El Cajete 

pyroclastic beds (Qvec).

Fires, Fluvial Geomorphology, and Slope 

Movements—Qfa includes both streamflow and debrisflow deposits, which increase following a fire.

Landscape Evolution—Middle Pleistocene to Holocene 

age is assigned based on a relatively low topographic 

position in the landscape.

QUATERNARY 

(Holocene to Pleistocene)

Alluvial deposit, beds of 

sand

(Qa5) 

River-deposited sand and pebbly sand, and thin beds of 

silty sand. Cross- to planar-bedded. Beds generally <0.5 m 

(2 ft) thick. Base not exposed. 

El Cajete Pyroclastic Beds—Qa5 is younger than El 

Cajete pyroclastic beds (Qvec; 60,000–50,000 years ago).

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported.

Landscape Evolution—Qa5 deposited by ancestral Rio 

Grande. Exposed beneath narrow terraces 3–10 m

(10–30 ft) above the modern Rio Grande. 

QUATERNARY 

(Holocene to Pleistocene)

Alluvial and eolian deposit

(Qpa) 

Consists of yellowish brown, pebbly, and silty-clayey sand. 

Mostly 1–2 m (3–7 ft) thick, with a possible maximum 

thickness of 8 m (26 ft).

Note: Although grouped with alluvial (river/channelized) 

and eolian (windblown) deposits in the GRI GIS data set, 

the unit was deposited by sheetwash (overland flow). It 

was originally mapped as sheetwash deposits by Dethier et 

al. (2011) and sheetflood deposits and minor eolian 

sediment by Konig and Read (2010) within the monument.

Bandelier Tuff—Qpa contains reworked pumice from 

Otowi Member of the Bandelier Tuff (Qbo).

Cerros del Rio Volcanic Rocks—most deposits of Qpa

include primary and reworked basaltic colluvium (e.g., 

QTcrv). 

El Cajete Pyroclastic Beds—most deposits include 

primary and reworked El Cajete pyroclastic beds (Qvec). 

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

Fires, Fluvial Geomorphology, and Slope 

Movements—deposited by sheetflooding (overland flow), 

which is common following a fire.

Landscape Evolution—Holocene age indicates ongoing 

processes (eolian, fluvial, and sheetwash).
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 2 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY 

(Holocene to Pleistocene)

Landslides

(Qls)

Gravity-deposited, poorly sorted debris. Thickness varies 

considerably depending on the size and nature of the 

landslide. 

Rio Grande Rift—failures mainly occurred along steeply 

dipping planes rooted in the Santa Fe Group, and in 

hydromagmatic deposits and other altered volcanic rock. 

Slide material commonly overlies rocks of the Santa Fe 

Group.

Cerros del Rio Volcanic Field—Qls commonly mantled 

by basaltic colluvium composed of Cerros del Rio volcanic 

rocks (Qcrv). 

El Cajete Pyroclastic Beds—older slides may be overlain 

by El Cajete pyroclastic beds (Qvec; 60,000–50,000 years 

ago).

Fires, Fluvial Geomorphology, and Slope 

Movements—depending on lithology and drainage-basin 

morphology, debris flows may be produced following a 

fire. 

Cliff Retreat and Rockfall—cliff retreat in Bandelier 

National Monument occurs as a result of deep-seated 

landslides. 

Cochiti Dam and Reservoir—holding of water beyond 

“temporary” time frames and lake drawdown reactivates 

landslides.

Rio Grande Rift, Peripheral Volcanism, Jemez 

Mountains Volcanic Field, and Landscape Evolution—

morphology and inclusion of Tshirege Member of the 

Bandelier Tuff (Qbt) in some Qls deposits suggests that 

they were active in early Pleistocene time, but many 

stabilized in middle to late Pleistocene time. 

QUATERNARY 

(Holocene to Pleistocene)

Colluvium

(Qc)

Primarily gravity-deposited, pebbly silty sand to cobbly and 

boulder rubble with sandy matrix. Thickness generally

4–10 m (10–30 ft), but locally exceeds 25 m (80 ft), for 

example in White Rock Canyon. 

Although abundant, Qc was mapped only where deposits 

are extensive or where they cover critical contact of fault 

relations.

Bandelier Tuff—Qc occurs at the base of cliffs that are 

commonly composed of Tshirege Member (Qbt).

El Cajete Pyroclastic Beds—deposits include El Cajete 

pyroclastic beds (Qvec) in many areas.

Cliff Retreat and Rockfall—Qc includes rockfall, debris 

flow, slope wash, and poorly sorted alluvium on slopes or 

at the base of cliffs in wedge-shaped deposits.

Seismic Activity—seismic shaking may induce rockfall and 

deposition of Qc.

Landscape Evolution

Holocene age indicates 

and Humans on the Landscape—

an ongoing process.

QUATERNARY 

(Holocene to Pleistocene)

Terrace gravel

(Qt)

Gravel deposited in previous stream channels now 

“perched” as terraces above the modern floodplain. 

Maximum thickness as much as 15 m (50 ft).

Mapped in only a few locations but relatively extensive 

along major streams such as El Rito de los Frijoles. 

None reported.

Fires, Fluvial Geomorphology, and Slope 

Movements—changes in channel geometry following a 

fire may affect Qt.

Landscape Evolution and Humans on the Landscape—

consists of slightly older alluvium that lies along the 

margins of present streams and basins; now undergoing 

erosion.

QUATERNARY 

(Holocene to Pleistocene)

Boulder fields

(Qrx)

High-elevation areas covered with boulders as large as 3 m 

(10 ft) across derived from subjacent rock units. Thickness 

unknown.

High-Elevation Features—Qrx, as well as rock glaciers, 

patterned ground, and felsenmeer occur at high elevations 

in the monument. 

None reported. 

Landscape Evolution—contemporaneous with landslide 

deposits (Qls) and terrace gravel (Qt) but likely predates 

their occurrence on the landscape. May be associated with 

Pleistocene (ice age) glaciations.

QUATERNARY 

(Late Pleistocene)

Alluvial deposit, gravel 

sand

(Qa4) 

and River-deposited, well-sorted cobble to boulder gravel, 

cross-bedded sand, and thin-bedded sand; and riverdeposited and windblown silty sand. Thickness probably

4–20 m (13–66 ft). 

Rio Grande Rift—Qa4 overlies Santa Fe Group deposits, 

landslide deposits, or older alluvium. 

El Cajete Pyroclastic Beds—Qa4 is younger than El 

Cajete pyroclastic beds (Qvec). 

Cochiti Dam and Reservoir—extensive 

Cochiti Dam.

deposits around Landscape Evolution—Qa4 consists of ancestral Rio 

Grande alluvium. Exposed beneath terrace remnants

14–20 m (46–66 ft) above the present-day stream channel.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 3 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY

(Late Pleistocene)

Piedmont alluvial deposit, 

gravel, sand and silty sand

(Qp4)

River-deposited, poorly sorted cobble to boulder gravel, 

sand, and local silty sand. Deposits 0.5–8.0 m (2–26 ft) 

thick. 

El Cajete Pyroclastic Beds—Qp4 is younger than El 

Cajete pyroclastic beds (Qvec). None reported.

Landscape Evolution—Qp4 makes up piedmont alluvial 

deposit west of the Rio Grande. Exposed beneath terraces 

14–20 m (46–66 ft) above present channels graded to the 

Rio Grande.

QUATERNARY

(Pleistocene)Tewa Group

Valles Rhyolite

El Cajete pyroclastic 

beds

(Qvec)

White to tan, moderately sorted, pyroclastic fall deposits of 

vesicular rhyolite. Consists of pumice clasts with a 

maximum diameter of about 15 cm (6 in); clast size 

diminishes from west to east away from source vent. 

Maximum exposed thickness varies from 70 m (230 ft) in 

vent area to scant exposures too thin to map.

Jemez Mountains Volcanic Field—emplaced in Valles 

caldera, following resurgent uplift of the caldera floor. 

Source was El Cajete crater.

Bandelier Tuff—Qvec is extensively reworked by erosion 

and collects on east-facing slopes and on benches cut into 

upper flow unit and/or cooling unit boundaries of Tshirege 

Member of Bandelier Tuff (Qbt).

El Cajete Pyroclastic Beds—significant time-stratigraphic 

marker in the area; deposited 60,000–50,000 years ago. 

Facilitated “dry farming” in the Jemez Mountains.

Fires, Fluvial Geomorphology, and Slope 

Movements—slopes mantled in pumice (Qvec) promote 

flooding.

Volcano Hazards—future hazards include ash and pumice 

deposited beyond caldera rim; similar to hazards during 

deposition of Qvec.

Jemez Mountains Volcanic Field—originated from El 

Cajete crater in southern part of Valles caldera.

Landscape Evolution and Humans on the Landscape—

forms extensive mesa-top cover in Bandelier National 

Monument.

QUATERNARY

(Pleistocene)Tewa Group

Valles Rhyolite

Older alluvium

(Qtoal)

River-deposited gravel, sand, and silt overlying Tshirege 

Member of Bandelier Tuff (Qbt) on the rim and flanks of 

Valles caldera. Maximum exposed thickness about 6 m

(20 ft).

Jemez Mountains Volcanic Field—contemporaneous 

with the most recent volcanism in the volcanic field. 

Emplaced in Valles caldera, following resurgent uplift of 

the caldera floor.

None reported.

Jemez Mountains Volcanic Field—maximum age of 

Qtoal is at least 1.1 million years. 

Landscape Evolution—largely pre-dates incision of 

canyons in surrounding plateaus and highlands.

QUATERNARY

(Pleistocene)Tewa Group

Valles Rhyolite

Young Rabbit 

Mountain debris-flow 

deposits

(Qrd2)

Qrd2 consists of two debris-flow deposits overlying 

Tshirege Member of Bandelier Tuff (Qbt) immediately 

south of Rabbit Mountain. Resembles Qrd1 (see 

description below) except that the matrix is not as ash rich. 

Maximum exposed thickness about 60 m (200 ft).

Jemez Mountains Volcanic Field—contemporaneous 

with the most recent volcanism in the volcanic field. 

Emplaced in Valles caldera, following resurgent uplift of 

the caldera floor.

None reported.

Jemez Mountains Volcanic Field—Qrd2 is younger than 

about 1.25 million years ago, when Young Rabbit 

Mountain dome formed.

QUATERNARY

(Pleistocene)Tewa Group

Bandelier Tuff

Tshirege Member

(Qbt)

White to orange to pink welded to nonwelded rhyolitic 

ash-flow tuff. Consists of ash fall (“pyroclastic fall”) and 

multiple pyroclastic flows (“ash flows”) in a compound 

cooling unit. Maximum observed thickness within caldera 

more than 900 m (2,950 ft). 

Jemez Mountains Volcanic Field—represents one of two

caldera-forming eruptions in the central part of the 

volcanic field. Eruption of Qbt resulted in the formation of 

Valles caldera, which largely obliterated Toledo caldera.

Bandelier Tuff—the most famous rock unit in the Jemez 

Mountains volcanic field, and possibly the most famous 

ash-flow tuff in the world. 

Features in Bandelier Tuff—Qbt contains cavates, and 

weathered to form tent rocks. Trails eroded into Qbt.

Paleontological Resources—ash deposits likely to contain 

fossils, though none reported within Bandelier National 

Monument to date. Cavates in Qbt may contain packrat 

middens (Neotoma spp.).

Cliff Retreat and Rockfall—erosion of Qbt tends to form 

cliffs. Rockfall from cliffs is the most common type of slope 

movement in Bandelier National Monument. 

Cavate Deterioration—cavates primarily impacted 

through small-scale spalling and granular erosion of 

Bandelier Tuff, and to a lesser extent from large-scale 

rockfall.

Jemez Mountains Volcanic Field—Qbt erupted

1.25 ± 0.01 million years ago (40Ar/39Ar age).

Humans on the Landscape—ancestral Puebloans 

hollowed out cavates for storage and habitation.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 4 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY 

(Pleistocene)Tewa Group

Cerro Toledo

Formation 

Pueblo Canyon 

Member

(Qcpc)

Colluvial deposit of reworked pumice and angular blocks of 

Otowi Member of Bandelier Tuff (Qbo) in middle Frijoles 

Canyon; two thin deposits of primarily Tschicoma 

Formation–derived gravels in upper Frijoles Canyon and 

northwest of Rendija Peak. Maximum thickness about 4 m 

(13 ft). 

Jemez Mountains Volcanic Field—consists of domes, 

flows, and pyroclastic deposits of Toledo caldera, and 

pyroclastic and contemporaneous volcaniclastic units 

between the two members of Bandelier Tuff (Qbo and 

Qbt). 

Cliff Retreat and Rockfall and Cavate Deterioration—

where exposed at the base of Tshirege cliffs in Frijoles 

Canyon, Qcpc facilitates cliff retreat, which negatively 

impacts archeological sites.

Jemez Mountains Volcanic Field—Qcpc deposited 

between the two cataclysmic explosions of Bandelier 

in the central part of the volcanic field.

Tuff 

QUATERNARY 

(Pleistocene)Tewa Group

Cerro Toledo

Formation 

Valle Toledo Member, 

Old Rabbit Mountain 

debris-flow deposits

(Qrd1)

Debris flows formed by multiple failures of the Rabbit 

Mountain dome during growth. Outcrops display sintered 

ashy matrix, suggesting formation as pyroclastic flows. 

Forms southeast-trending hummocky tongue 5 km (3 mi) 

long and 3 km (2 mi) wide. Maximum exposed thickness 

about 40 m (130 ft). 

Jemez Mountains Volcanic Field—deposited between 

the two cataclysmic explosions of Bandelier Tuff in the 

central part of the volcanic field. Formed in Toledo caldera 

during eruption of Rabbit Mountain (lava dome). 

Lithic Resources—Qrd1 contains abundant obsidian 

blocks that are a known source of artifacts. 

None reported.

Jemez Mountains Volcanic Field—Qrd1 deposited 

between lower and upper Bandelier Tuffs during the Cerro 

Toledo interval. 

Human on the Landscape—Qrd1 contains obsidian used 

for making tools.

QUATERNARY 

(Pleistocene)Tewa Group

Cerro Toledo

Formation 

Valle Toledo Member, 

Rabbit Mountain 

rhyolite

(Qcrm)

Makes up Rabbit Mountain (lava dome) and thick flows 

and flow breccias of rhyolitic composition. Maximum 

exposed thickness about 410 m (1,345 ft).

Jemez Mountains Volcanic Field—deposited between 

the two cataclysmic explosions of Bandelier Tuff in the 

central part of the volcanic field. Vent for Qcrm collapsed 

before or during formation of Valles caldera.

Lithic Resources—Qcrm contains obsidian and is a known 

source of artifacts.

None reported.

Jemez Mountains Volcanic Field—Qcrm deposited 

between Otowi and Tshirege members of Bandelier Tuff. 

Potassium/argon (K/Ar) ages of 1.43 million ± 0.04 million 

and 1.54 ± 0.06 million years ago.

Human on the Landscape—Qcrm contains obsidian used 

for making tools.

QUATERNARY 

(Pleistocene)Tewa Group

Cerro Toledo

Formation 

Valle Toledo Member

(Qct)

Consist of rhyolitic pyroclastic fall deposits usually less than 

2 m (7 ft) thick. Maximum exposed thickness about 20 m 

(70 ft) but exceeds 30 m (100 ft) in several wells drilled on 

the Pajarito Plateau. 

Jemez Mountains Volcanic Field—Qct deposited 

between the two cataclysmic explosions of Bandelier Tuff 

in the central part of the volcanic field. Tuffaceous layers 

are part of the Cerro Toledo rhyolite originating from 

sources in Toledo caldera.

Lithic Resources—obsidian phase is completely aphyric 

(“fine grained”) and a known source of artifacts.

None reported.

Jemez Mountains Volcanic Field—Qct deposited 

between lower and upper Bandelier Tuffs during the Cerro 

Toledo interval. Ages of tuffaceous units and source domes 

range from 1.64 million to 1.21 million years ago. 

Human on the Landscape—used obsidian for making 

tools.

QUATERNARY 

(Pleistocene)Tewa Group

Bandelier Tuff

Otowi Member

(Qbo)

Poorly to densely welded rhyolitic ash-flow tuff. Very 

difficult to distinguish from Qbt in hand samples; best 

distinguished by poorer degree of welding, greater 

tendency to form slopes instead of cliffs, more abundant 

lithic fragments, less abundant iridescent sanidine, and 

stratigraphic position beneath the Tsankawi Pumice and/or 

Cerro Toledo Formation. Maximum exposed thickness 

about 120 m (390 ft).

Jemez Mountains Volcanic Field—represents one of two 

caldera-forming eruptions in the central part of the 

volcanic field. Eruption of Qbo resulted in the formation of

Toledo caldera. Discontinuously fills in rugged topography 

on a pre–Toledo caldera age volcanic surface; upper 

surface undulatory due to erosion.

Bandelier Tuff—Qbo is part of the most famous rock unit 

in the Jemez Mountains volcanic field, and possibly the 

most famous ash-flow tuff in the world. 

Features in Bandelier Tuff—contains tent rocks.

Cliff Retreat and Rockfall—Qbo has greater tendency to 

form slopes than Tshirege Member (Qbt).

Jemez 

1.61 ± 

ages). 

Mountains Volcanic Field—Erupted 

0.01 to 1.62 ± 0.04 million years ago (40Ar/39Ar 

Paleontological Resources—ash deposits likely to contain 

fossils, though none reported within Bandelier National 

Monument to date.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 5 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY

(Middle? Pleistocene)

Alluvial deposit, boulder 

gravel and cross-bedded 

sand

(Qa3)

River-deposited, well-sorted cobble to poorly sorted 

boulder gravel, cross-bedded sand, and thin-bedded sand, 

preserved at mouths of tributaries and in an extensive 

deposit near Alamo Canyon that contain angular boulders 

as large as 3.5 m (11 ft). Thickness 4–15 m (13–49 ft). 

Jemez Mountains Volcanic Field—Qa3 consists of clasts 

of predominantly axial river lithologies but locally rich in 

andesitic and dacitic rocks derived from volcanic terrane to 

the west.

Rio Grande Rift—Qa3 overlies and truncates rocks of the 

Santa Fe Group, landslide deposits, older alluvium, or 

hydromagmatic deposits.

El Cajete Pyroclastic Beds—extensive deposits on both 

sides of Rio Grande near the mouth of Alamo Canyon are 

overlain by El Cajete pyroclastic beds (Qvec). 

None reported.

Landscape Evolution—Qa3 is composed of ancestral Rio 

Grande alluvium. Exposed beneath terrace remnants

25–45 m (80–150 ft) above the Rio Grande.

QUATERNARY

(Middle? Pleistocene)

Piedmont alluvial deposit, 

poorly sorted gravel and 

sand

(Qp3)

Poorly sorted cobble to boulder gravel and sand at the base 

of mountain slopes. Thickness 0.5–8.0 m (2–26 ft). 

El Cajete Pyroclastic Beds—Qp3 is older than El Cajete 

pyroclastic beds (Qvec). None reported.

Rio Grande Rift and Jemez Mountains Volcanic Field—

Qp3 locally overlies Cochiti Formation (QTc), Otowi 

Member of Bandelier Tuff (Qbo), or Santa Fe Group 

deposits.

Landscape Evolution—piedmont alluvial deposits west 

and east of the Rio Grande. Exposed beneath terraces

25–40 m (80–130) above present channels.

QUATERNARY

(Middle? Pleistocene)

Alluvial deposit, cobble and 

boulder gravel

(Qa2)

River-deposited, well-sorted cobble to boulder gravel. 

Boulders as large as 3 m (10 ft) across. Thickness generally 

10–30 m (30–100 ft). 

El Cajete Pyroclastic Beds—Qa2 is older than El Cajete 

pyroclastic beds (Qvec).

Paleontological Resources—amino-acid ratios from 

gastropods in the upper 5 m (16 ft) of Qa2 suggest a local 

age of 300,000 to 250,000 years ago.

None reported.

Landscape Evolution—Qa2 is composed of Rio Grande 

alluvium. Exposed beneath terrace remnants approximately 

50 to 70 m (160 to 230 ft) above the present Rio Grande 

channel.

QUATERNARY

(Middle? Pleistocene)

Piedmont alluvial deposit, 

gravel, silt and massive 

sand

(Qp2)

Poorly sorted cobble to boulder gravel and massive sand 

and local silt beds.

El Cajete Pyroclastic Beds—Qp2 is older than El Cajete 

pyroclastic beds (Qvec). None reported.

Rio Grande Rift and Jemez Mountains Volcanic Field—

Qp2 locally overlies Cochiti Formation (QTc), Otowi 

Member of Bandelier Tuff (Qbo), or Santa Fe Group 

deposits.

Landscape Evolution—Qp2 was deposited west and east 

of the Rio Grande. Exposed beneath terrace remnants

45–60 m (150–200 ft) above present channels. 

QUATERNARY

(Early Pleistocene)

Andesite of Cochiti 

Volcano, lower unit

(Qcl)

Reddish brown to medium gray andesite. Maximum 

exposed thickness is 350 m (1,150 ft).

Cerros del Rio Volcanic Field—Qcl consists of lava flows 

and oxidized cinder and spatter erupted from Cochiti 

volcano in the Cerros del Rio volcanic field. 

Seismic Activity—Cochiti volcano deposits post-date 

down-to-west offset along the Cochiti fault, whose 

footwall scarp formed a topographic barrier to eastward 

deposition of lava flows.

Peripheral Volcanism—Qcl is part of the Cerros del Rio 

volcanic field. Erupted 1.7 million–1.5 million years ago.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 6 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY and TERTIARY

(Lower Pleistocene to upper Pliocene)

Cerros del Rio 

volcanic rocks

(QTcrv)

Basalt, basaltic andesite, andesite, and dacite. Silica content 

ranges from 48%–65% (mostly 48%–60%). 

Phreatomagmatic deposits (pale brown to very pale brown 

silty sand with 3%–20% pebbles) and lapilli (black and in 

very thin, planar to wavy, even beds or laminations) 

generally underlie the package of flows. Thickness of the

volcanic pile ranges from a few meters along the eastern 

margin to 100–240 m (330–790 ft) in the central part of 

the Caja del Rio plateau.

Cerros del Rio Volcanic Field—lava flows and associated 

phreatomagmatic deposits. Primarily cap the Caja del Rio 

plateau. Central-vent volcanoes typify the eruptive centers 

in this field, and range from low-relief shields to steepsided, breached cinder cones.

Lithic Resources—dacitic lavas (>63% SiO2) are related to 

late-stage dome growth and eruption of viscous, blocky 

lava flows as much as 50 m (160 ft) thick in the Cerros del 

Rio volcanic field. Ancient people utilized a dacite quarry in

this material at the mouth of Alamo Canyon in Bandelier 

National Monument.

Cochiti Dam and Reservoir—dam constructed on three 

extinct volcanoes of Santa Ana Mesa, which are 

contemporaneous with Cerros del Rio volcanoes.

Peripheral Volcanism—erupted from the Cerros del Rio 

vents. Age of the volcanic rocks ranges from 2.7 million to 

1.0 million years ago, with most 2.7 million–2.2 million 

years ago. 

Humans on the Landscape—QTcrv contains dacite used 

for making tools.

TERTIARY

(Pliocene)

Mafic lava flows

(Tclf)

Basaltic rock in undivided unit of flows, dikes, and 

associated cinder deposits. Flows massive to sheeted, 

generally showing broad columnar joints. May contain 

abundant xenocrysts of rocks from beneath the Pajarito 

Plateau that were transported upward during a volcanic 

eruption. Maximum exposed thickness about 40 m (130 ft).

Cerros del Rio Volcanic 

del Rio volcanic field.

Field—Tclf erupted in the Cerros None reported. Peripheral Volcanism—age range from 2.8 million to

2.3 million years ago (40Ar/39Ar ages). 

TERTIARY

(Pliocene)

Benmorite

(Tcba)

Basaltic rock in thick lava flow exposed in upper walls of 

lower Frijoles Canyon and adjacent White Rock Canyon. 

Locally contorted and flow banded within upper two-thirds 

of flow. Lower part of flow generally massive and cut by 

widely spaced columnar joints. Maximum exposed 

thickness about 70 m (230 ft).

Cerros del Rio Volcanic Field—Tcba

Cerros del Rio volcanic field.

erupted in the None reported. Peripheral Volcanism—Tcba

years ago (40Ar/39Ar age).

erupted 2.75 ± 0.08 million 

TERTIARY

(Pliocene)

Cinder deposit

(Tcbc)

Basaltic rock in scoria, bombs, and associated thin lavas 

from partially exposed cone in eastern wall of Frijoles 

Canyon just upstream of Upper Frijoles Falls. Maximum 

exposed thickness about 25 m (82 ft).

Cerros del Rio Volcanic Field—Tcbc

Cerros del Rio volcanic field.

erupted in the None reported. Peripheral Volcanism—relations with other Cerros del Rio 

rocks uncertain. 

TERTIARY

(Pliocene)

Mafic hydromagmatic 

deposits

(Tcbm)

Layered hydromagmatic (maar) deposits, consisting of 

cinders, ash, and decomposed glass with pebble- to 

boulder-sized fragments of rocks from beneath the Pajarito 

Plateau that were brought to the surface during volcanism. 

Magmatic component is primarily basalt. Contains 

numerous interbedded, mafic lava flows too thin or 

discontinuous to map. Maximum exposed thickness about 

150 m (490 ft).

Cerros del Rio Volcanic Field—Tcbm is the result of 

magma–water interactions in the Cerros del Rio volcanic 

field.

None reported.

Rio Grande Rift—Tcbm contains beds and lenses of 

ancestral Rio Grande gravels. 

Peripheral Volcanism—formed by interaction of mafic 

magmas with shallow groundwater or surface water about 

2.78 ± 0.04 million years ago (40Ar/39Ar age).

TERTIARY

(Pliocene)

Basalt of La Bajada Rim

(Tb)

Medium- to dark-gray basalt (48%–50% silica). Maximum 

exposed thickness 40 m (130 ft).

Cerros del Rio Volcanic Field—likely erupted from buried 

and/or eroded volcanic centers overlain by the andesite of 

Cochiti Volcano, upper unit (Qcu).

Seismic Activity—exposed principally along topographic 

rim of the La Bajada fault escarpment (southeastern part of 

Bandelier National Monument). Lava flows occur locally to 

the west of the La Bajada fault escarpment in the hanging 

wall of the fault.

Peripheral Volcanism—Tb erupted 2.57 ± 0.02 million 

years ago (40Ar/39Ar age). 

Humans on the Landscape—Tb contains basalt used for 

making tools.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 7 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

TERTIARY

(Pliocene)

Hydromagmatic deposits

(Tbhm)

Basaltic tuff and cinders, and thin (<10 m [30 ft]), 

interlayered basaltic flows. Ash fall beds, 0.3–3.0 m

(1–10 ft) thick, composed mainly of ash and lapilli 

containing sparse bombs of accidental and basaltic 

fragments. Surge beds are planar and cross-bedded, locally 

rippled, coarse silt to pebbly sand, generally 0.1–0.4 m 

(0.3–1.3 ft) thick. Flowage deposits mainly matrix-rich 

pebble to boulder gravel in discontinuous beds 1–4 m

(3–13 ft) thick. Locally sheared, slumped, or brecciated. 

Rio Grande Rift—includes accidental fragments of the 

Santa Fe Group.

Cerros del Rio Volcanic Field—Tbhm deposited as 

bedded to massive fall, surge, and flow deposits. 

None reported.

Rio Grande Rift—Tbhm is contemporaneous with

paleochannel deposits of the Rio Grande (river).

Peripheral Volcanism—Tbhm is older than approximately 

2.5 million years; maximum age not closely constrained.

TERTIARY

(Pliocene)

Andesite of Sanchez 

Canyon

(Tas)

Medium gray to reddish brown andesite (56% silica). 

Consists of lava flows and associated near vent pyroclastic 

deposits. Lava flows are discontinuous and variable in 

thickness from 1.5 m (5 ft) to tens of meters thick, 

depending on local underlying paleotopography. Locally 

includes oxidized andesitic scoria, breccia, spatter, and 

spatter agglutinate interbedded with lava flows. Maximum 

thickness is 100 m (330 ft). 

Cerros del Rio Volcanic Field—exposed along the Rio 

Grande principally between Bland Canyon on the south 

and Capulin Canyon on the north (southeast corner of 

Bandelier National Monument).

None reported. Peripheral Volcanism—Tas erupted in the Cerros del Rio 

volcanic field.

TERTIARY

(Pliocene)

Andesite and basaltic 

andesite, undivided

(Taba)

Undifferentiated deposits of andesite and basaltic andesite 

lava flows and associated breccias; some interbedded 

pyroclastic and/or hydromagmatic deposits. Maximum 

exposed thickness 130 m (430 ft). 

Cerros del Rio Volcanic Rocks—Taba erupted in the 

Cerros del Rio volcanic field. None reported.

Rio Grande Rift—Taba is contemporaneous with

paleochannel deposits of the Rio Grande (river).

Peripheral Volcanism—Taba emplaced about 3 million 

years ago.

QUATERNARY and TERTIARY

(Lower Pleistocene and Pliocene)

Santa Fe Group

Axial channel facies

(QTsfa)

Slightly lithified pebble to cobble gravel rich in rounded 

clasts, arkosic sand, and thin beds of silty sand. Coarse 

units are 0.5–3.0 m (2–10 ft) thick, massive to crossbedded, and locally planar-bedded. Gravel generally >70% 

quartzite, granite, and other resistant rocks from northern 

New Mexico; andesitic and dacitic rocks from the Jemez 

Mountains common locally; vesicular basalt uncommon. 

Matrix quartzose or arkosic. Thickness 5 to >70 m

(16 to >230 ft).

Rio Grande Rift—QTsfa is part of the Santa Fe Group. 

Lies beneath landslide deposits, Pliocene basalt, or 

hydromagmatic deposits at most exposures. Fills channels 

in and locally interbedded with Cochiti Formation (QTc) of 

the Keres Group. 

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported. Rio Grande Rift—QTsfa filled in developing Española 

basin.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 8 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

QUATERNARY and TERTIARY

(Lower Pleistocene to lower Pliocene) 

Keres Group

Puye Formation

ancestral Rio Grande 

facies

(QTpt) 

Slightly lithified pebble to cobble gravel (with abundant 

clasts of Proterozoic quartzite and granite), sand, and thin 

beds of silty sand. Thickness 5–45 m (16–150 ft).

Jemez Mountains Volcanic Field—extensive 

volcanogenic alluvial fan complex shed eastward from 

volcanic domes and flows of the Tschicoma Formation 

(e.g., Ttpm, Ttcg, and Ttsd). Displays considerable lateral 

variation, consisting of complex, intertonguing mixtures of 

streamflow, sheet flow, debris flow, block and ash flow, 

pumice fall, and ignimbrite deposits.

Rio Grande Rift—Qtpt is generally found west of the 

modern Rio Grande. East of the Rio Grande, it is exposed 

at one outcrop south of the mouth of Cañada Ancha. Qtpt

interfingers with the Puye Formation fanglomerate and 

underlies the fanglomerate in upper White Rock Canyon. 

The Puye Formation pre-dates overlying Cerros del Rio 

volcanic rocks (2.2 million–2.7 million years ago).

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported.

Rio Grande Rift—QTpt deposited by the ancestral Rio 

Grande during the Pliocene Epoch. Contemporaneous with 

the Tschicoma Formation. QTpt lies beneath landslide 

deposits, Pliocene alluvium, or phreatomagmatic deposits 

at most exposures, indicating an age of 5.3 million to

2.7 million years ago.

QUATERNARY and TERTIARY

(Lower Pleistocene to Miocene)

Keres Group

Cochiti Formation

(QTc)

Thick sequence of volcanic gravel and sand (alluvial fans) 

derived from penecontemporaneous erosion of volcanic 

units of the Keres Group. Consists of weakly lithified 

pebble to cobble gravel, massive to planar-bedded sand, 

thin (<0.3 m [1 ft]) beds of rhyolitic tephra and pumiceous 

alluvium, beds of fine sand and silt, and silt-rich debris 

flows containing volcanic clasts. Maximum exposed 

thickness about 450 m (1,480 ft).

Jemez Mountains Volcanic Field—QTc consists of 

volcaniclastic material shed from domes of Bearhead 

Rhyolite (Tbh), primarily as lahars, block and ash flows, and 

other debris flows that accumulated in small basins and 

topographic lows between volcanoes. Locally contains 

hyperconcentrated flow and fluvial deposits, cinder 

deposits, and pyroclastic fall deposits.

Rio Grande Rift—QTc generally thickens to the south, 

east, and north into the developing basin of the Rio 

Grande rift, forming coalesced but eroded alluvial fans.

None reported.

Rio Grande Rift and Jemez Mountains Volcanic Field—

much stratigraphic confusion with QTc, but deposited 

during Keres volcanism (approximately 13 million–6 million 

years ago). 

TERTIARY

(Pliocene)

Keres Group

Tschicoma Formation

Pajarito Mountain 

dacite

(Ttpm) 

Consists of voluminous domes (e.g., Tschicoma and 

Polvadera peaks) and flows of dacite. Maximum exposed 

thickness about 365 m (1,200 ft).

Jemez Mountains Volcanic Field—Ttpm erupted from 

vents mostly in the northern part of the volcanic field. 

Source was Pajarito Mountain.

Lithic Resources—Ttpm is too porphyritic for making 

tools and projectile points. 

None reported.

Jemez Mountains Volcanic Field—40Ar/39Ar ages on 

geographically separated samples range from 3.09 million 

to 2.93 million years ago.

TERTIARY

(Pliocene)

Tschicoma Formation

Cerro Grande dacite

(Ttcg) 

Consists of extensive dome and flow complex of dacite. 

Maximum exposed thickness about 750 m (2,460 ft).

Jemez Mountains Volcanic Field—Ttcg erupted from 

vents mostly in the northern part of the volcanic field. 

Source was Cerro Grande.

Lithic Resources—Ttcg is too porphyritic for making tools 

and projectile points.

None reported.

Jemez Mountains Volcanic Field—erupted from

3.35 million to 2.88 million years ago, as estimated from

ages on widely separated samples.
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 9 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

TERTIARY

(Pliocene)

Keres Group

Tschicoma Formation

Sawyer Dome dacite

(Ttsd)

Consists of dome and flow complex of dacite. Maximum 

exposed thickness is 245 m (800 ft). 

Jemez Mountains Volcanic Field—erupted from vents 

mostly in the northern part of the volcanic field.

Lithic Resources—Ttsd is too porphyritic for making tools 

and projectile points.

None reported. Jemez Mountains Volcanic Field—Ttsd erupted

3.44 ± 0.30 million years ago (40Ar/39Ar age).

TERTIARY

(Pliocene to 

Miocene)

Keres Group

Bearhead Rhyolite

(Tbh)

Consists of domes, shallow intrusions (e.g., dikes and 

plugs), flows, and pyroclastic rocks of rhyolitic composition. 

Some domes (e.g., Bearhead Peak) are quite voluminous. 

Locally shows pervasive hydrothermal alteration. Maximum 

observed thickness about 100 m (330 ft).

Jemez Mountains Volcanic Field—Tbh erupted from 

vents in the southern part of the volcanic field. None reported.

Jemez Mountains Volcanic Field—Tbh erupted between 

7.83 million to 4.81 million years ago, as estimated from 40Ar/39Ar ages on widely separated samples.

TERTIARY

(Miocene)

Keres Group

Bearhead Rhyolite

Peralta Tuff Member

(Tkpt)

White to tan, lithic-rich, ash fall tuff. Includes major 

sequences of pyroclastic rocks consisting of fall, flow, 

surge, and hydromagmatic surge deposits that were 

erupted from different vents. Sources for all tuff units 

unknown. Fills in rugged volcanic topography on earlier 

Keres Group rocks. Maximum observed thickness about 

170 m (560 ft).

Jemez Mountains Volcanic Field—Tkpt erupted from 

vents in the southern part of the volcanic field. None reported.

Jemez Mountains Volcanic Field—Tkpt erupted

6.81 ± 0.15 million years ago (K-Ar age of lowermost tuff 

bed at Peralta Canyon type locality).

TERTIARY

(Pliocene to Miocene)

Santa Fe Group, undivided

(Tsf)

White to tan to very pale green feldspathic sandstone, as 

well as siltstone and conglomerate. Maximum observed 

thickness 200 m (660 ft).

Rio Grande Rift—Tsf was deposited by the ancestral Rio 

Grande (river) in the Rio Grande rift as Earth’s crust pulled 

apart.

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported. Rio Grande Rift—Tsf deposited in the rift.

TERTIARY

(Miocene)

Keres Group

Paliza Canyon 

Formation

Porphyritic dacite tuff

(Tpdt)

White pumice, ash, crystals, and lithic fragments commonly 

found in volcaniclastic deposits of the Paliza Canyon 

Formation. Consists of pyroclastic fall deposits. Beds are 

not laterally extensive and pinch out due to erosion. May 

show reverse or graded bedding. Maximum exposed 

thickness about 40 m (130 ft). 

Jemez Mountains Volcanic Field—Tpdt erupted from 

vents in the southern part of the volcanic field.

Lithic Resources—Tpdt consists of dacite.

None reported.

Jemez Mountains Volcanic Field—erupted

8.20 ± 0.29 million years ago (K-Ar age of altered tuff).

Humans on the Landscape—Tpdt contains dacite used 

for making tools.

TERTIARY

(Miocene)

Keres Group

Paliza Canyon 

Formation

Porphyritic hornblende 

dacite

(Tphd)

Gray to pink porphyritic dacite. Consists of domes, flows, 

and minor intrusive rocks. Flows massive to sheeted; may 

contain flow breccia. Eroded flows cap the summits of Las 

Conchas, Los Griegos, and other hills south of Valles 

caldera. Maximum exposed thickness is 75 m (250 ft). 

Jemez Mountains Volcanic Field—Tphd erupted from 

vents in the southern part of the volcanic field.

Lithic Resources—Tphd consists of dacite.

None reported.

Jemez Mountains Volcanic Field—erupted

8.53 ± 0.63 million years ago (40Ar/39Ar age from Los 

Griegos).

Humans on the Landscape—Tphd contains dacite used 

for making tools.

TERTIARY

(Miocene)

Keres Group

Paliza Canyon 

Formation

Porphyritic andesite

(Tppa)

Gray to black coarse porphyritic andesite. Consists of 

domes and flows. Flows generally sheeted with minor flow 

breccia. Maximum observed thickness about 150 m

(490 ft). 

Jemez Mountains Volcanic Field—Tppa erupted from 

vents in the southern part of the volcanic field. None reported. Jemez Mountains Volcanic Field—erupted

8.69 ± 0.38 million years ago (K-Ar age).
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 10 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

TERTIARY

(Miocene)

Keres Group

Paliza Canyon 

Formation 

Two-pyroxene 

andesite, undivided

(Tpa) 

Consists of domes, flows, flow breccia, spatter deposits, 

and scoria of andesite. Maximum exposed thickness about 

150 m (490 ft).

Jemez Mountains Volcanic Field—Tpa erupted from 

multiple, widely scattered vents in the southern part of the 

volcanic field.

None reported. Jemez Mountains Volcanic Field—erupted from 

9.4 million to 8.2 million years ago (40Ar/39Ar ages).

TERTIARY

(Miocene)

Keres Group

Canovas Canyon 

Rhyolite

(Tcct) 

White to pink tuffs, consisting of several distinct deposits, 

including lowermost unit of pink, lithic-rich tuff containing 

abundant fragments of flow banded rhyolite (informally 

named the "pink tuff”). Consists of as ash-fall and ashflow tuffs. Maximum exposed thickness about 10 m (30 ft).

Jemez Mountains Volcanic Field—Tcct erupted from 

vents in the southern part of the volcanic field. None reported. Jemez Mountains Volcanic Field—erupted 

10 million years ago.

about

TERTIARY

(Late Miocene)

Basalt flows and cinders

(Tsfb) 

Black alkali basalt and basanite (category of basaltic 

volcanic rocks). Consists of thin discontinuous flows, pillow 

basalt, and palagonite tuff. Maximum observed thickness 

about 5 m (16 ft).

Rio Grande Rift—Tsfb represents basaltic volcanism 

associated with formation of the Rio Grande rift. 

Interbedded with Santa Fe Group deposits

None reported.

Rio Grande Rift—part of minor basaltic volcanism that 

erupted into sediments of the Santa Fe Group

16.5 ± 1.4 million years ago (K-Ar age).

TERTIARY

(Miocene)

Chamita Formation

Lower Vallito Member

(Tscv) 

Buff colored, strongly to weakly cemented fine to coarse 

grained sandstone. Locally cross-bedded to planar 

laminated, otherwise massive. Contains two light gray to 

white chert beds in the lower 100 m (330 ft). Thickness 

about 250 m (820 ft).

Rio Grande Rift—Tesuque and Chamita formations are 

part of the Santa Fe Group. Tscv was deposited by the 

ancestral Rio Grande (river) in the Rio Grande rift.

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported.

Rio Grande Rift—Tscv was deposited by the ancestral Rio 

Grande (river) in the Rio Grande rift as Earth’s crust pulled 

apart.

TERTIARY

(Miocene)

Tesuque Formation

Chama-El Rito Member

(Tstc) 

Orange to pinkish quartz-rich sandstone with a few thin 

lenses of volcanic pebbles derived from volcanic fields to 

the north (Latir). Dominated by a sandy bed load. At least 

200 m (660 ft) thick.

Rio Grande Rift—Tesuque and Chamita formations are 

part of the Santa Fe Group. Tstc was deposited by the 

ancestral Rio Grande (river) in the Rio Grande rift. 

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported. Rio Grande Rift—deposited in the rift by a south-flowing 

(from the San Luis Basin) ancestral Rio Grande (river). 

TERTIARY

(Miocene)

Olivine andesite

(Tpoa) 

Black to gray slightly porphyritic andesite. Flows massive to 

sheeted, commonly with vesicular flow tops. Maximum 

observed thickness about 70 m (230 ft). 

Rio Grande Rift—domes, flows, and minor red cinder 

deposits associated with the formation of the Rio Grande 

rift.

None reported. Rio Grande Rift—basaltic volcanism in the 

Ages of various flows unknown.

Rio Grande rift. 

TERTIARY

(Miocene to upper Oligocene)

Tesuque Formation

Basalt flow

(Tstb) 

Exposures of flow and pillow-palagonite tuff east of St. 

Peter's Dome of black alkali basalt. Thickness about 3 m 

(10 ft).

Rio Grande Rift—Tesuque and Chamita formations are 

part of the Santa Fe Group. Tstb represents basaltic 

volcanism in sediments of the Santa Fe Group.

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

None reported.

Rio Grande Rift—deposited in the rift between

25.48 ± 0.84 million and 20.83 ± 0.63 million years ago, as 

estimated from interbedded basalt lava (40Ar/39Ar ages).
These units were mapped within Bandelier National Monument. A full list and descriptions of all 251 units in the GRI GIS data set for the monument are included in the GRI ancillary map information document (band_geology.pdf). Bold text in the table 

highlights sections in the report. Rocks of the Jemez Mountains volcanic field are divided into two major groups: Keres and Tewa. Rocks of the Santa Fe Group filled the Rio Grande rift. Rocks of the Cerros del Rio volcanic field are peripheral to the Jemez

Mountains volcanic field. The units in this table are ordered chronologically and, in some instances, vary from the order provided in the GRI GIS data and band_geology.pdf, which are grouped by formation name and/or geomorphologic type.

Map Unit Properties Table: Bandelier National Monument, Page 11 of 11

Age Map Unit

(Symbol) Geologic Description Geologic Features and Processes Geologic Resource Management Issues Geologic History

TERTIARY

(Miocene to upper Oligocene)

Volcaniclastic sediments

(Tstv) 

Black alkali basalt. Exposures of flow and pillow palagonite 

tuff. Thickness about 3 m (10 ft).

Rio Grande Rift—Tstv represents basaltic volcanism 

associated with formation of the Rio Grande rift. None reported.

Rio Grande Rift—Tstv is interbedded with Santa Fe 

Group deposits between 25.48 ± 0.84 million and

20.83 ± 0.63 million years ago (40Ar/39Ar ages).

PALEOGENE

(Eocene)

Galisteo Formation

(Tgs) 

Orange to tan to brick red beds of well-indurated 

sandstone, siltstone, arkose, and conglomerate. Maximum 

observed thickness about 200 m (660 ft). Base of unit not 

exposed.

Paleontological Resources—likely to contain fossils, 

though none reported within Bandelier National 

Monument to date.

Seismic Activity—Tgs is exposed on rotated fault block 

with beds dipping steeply west.

Tgs predates development of the Jemez Mountains 

volcanic field and formation of the Rio Grande rift. 

Deposited by rivers in a broad, deep inland basin,

56 million–33 million years ago.