o rapid downslope transport of surficial materials or 

n an inclined failure surface that separates the displaced 

At the scale of this map, only the larger, well-defined 

ows, rock and earth slumps, translational slides, debris 

x slides) (Varnes, 1978). Areas of talus (rockfall) and 

LIDE RECOGNITION

eviously unrecognized and unmapped deposits have 

quadrangle by reconnaissance surficial geologic mapping. 

thflows and rock slumps (less than 0.10 km2) to large 

debris avalanches, and complex landslides greater than 

underlie about 4 percent of the map area, and about 230 

lides or are within 100 m of a landslide. This estimate 

dicated on the Los Alamos 30′ × 60′ quadrangle base 

ighways, light-duty roads, unimproved roads, and trails).

ere identified and mapped by a variety of methods 

ogic maps, (2) stereoscopic analysis of 1:40,000-scale 

econnaissance fieldwork. Low sun angle in the early 

bdued topography of many older landslide deposits and 

ield. Physical characteristics common to landslides that 

dwall scarps, (2) hummocky topography, including closed 

toes, (4) deflection of stream channels by landslide toes, 

nd adjacent stable areas, (6) bedrock blocks with 

 coherent masses of geologic units downslope from their 

y, and topographic relief between the head and toe 

osits are more than 200 m thick (Reneau and Dethier, 

NDSLIDES IN THE MAP AREA

mos 30′ × 60′ quadrangle. East of the Sierra 

edges of volcanic mesas above major canyons. These 

nt volcanic rock are underlain by weakly indurated 

many cases, large blocks of volcanic rock have broken 

 the top of the block rotating back toward the mesa. In 

many of the failures occur in clay-rich units within the 

s in White Rock Canyon were mapped by Smith and 

 Mountains and later studied in detail by Reneau and 

and Dethier and Reneau (1996). Massive landslides also 

n de San Diego, (2) Vallecito Creek, and (3) the Rio 

 Rio Cebolla and the Rio de las Vacas. Here, landslides 

strength within the Pennsylvanian Madera and Triassic 

 Along the flanks of the Sierra Nacimiento, where 

alline rocks, the landslides occur mainly in the Madera 

and Chinle Formations (Woodward, 1987). In places, landslides form continuous, or nearly continuous, deposits for as much as 10 km along the sides of these canyons.

AGE OF LANDSLIDES

Landsliding on the Los Alamos 30′ × 60′ quadrangle probably began in the early to middle 

Pleistocene and was probably more active during the Pleistocene Epoch, which ended about 10,000 years ago, when the climate was relatively wetter than the present day. Hence, many of the landslide deposits shown on the map may now be relatively stable. In White Rock Canyon, extensive landsliding is thought to have begun in the middle Pleistocene, after the Rio Grande had incised through Pleistocene volcanic rocks and into weakly indurated sediments of the Santa Fe Group (Reneau and Dethier, 1996a). However, landsliding continues to be an ongoing process, as indicated by the damage to State highway 126 along the western side of the San Antonio Creek valley during the spring of 1998. Active slides also occur along the margin of Cochiti Lake and at Otowi along the Rio Grande.

FACTORS CONTRIBUTING TO LANDSLIDES

Several factors are thought to be responsible for many of the landslides in the Los Alamos 30′ × 

60′ quadrangle including: (1) downcutting of canyons through volcanic rocks exposing underlying weakly indurated sedimentary rocks of low shear strength, (2) continued downcutting and removal of lateral support during times of high stream flow, resulting in the maintenance of steep slopes, and (3) increases in pore water pressure in bedrock and surficial deposits, particularly during pluvial periods of the Pleistocene Epoch (Reneau and Dethier, 1996a). Because the map area is traversed by part of the Rio Grande rift, a seismically active area containing numerous faults with Pleistocene offset (Olig and others, 1996), many of the landslides may have been triggered by earthquakes.

IMPORTANCE OF LANDSLIDE RECOGNITION

Recognition of these landslides is important because natural and human-induced factors can 

influence slope stability. Reduction of lateral support (by excavations or roadcuts), removal of vegetation (by fire or development), or an increase in pore pressure (by irrigation or lake-level fluctuations) may result in reactivation of these landslides or parts of these landslides. The damming of a drainage by a landslide can create a temporary lake that overflows and bursts the dam, flooding downstream areas. Landsliding in White Rock Canyon is known to have dammed the Rio Grande at least four times between 12,000 and 18,000 radiocarbon years ago, and at about 40,000 radiocarbon years ago, and doubtless many times before that (Reneau and Dethier, 1996a).

LIMITATIONS OF MAP

Landslide deposits shown on this map are thought to underrepresent the actual number and 

aerial extent of landslides present for several reasons: (1) many small landslide deposits (<0.01 km2) 

probably were not recognized because of the scale (1:40,000) of the air photos used in this study, (2) extensive areas of shadows on some air photos made interpretation difficult, and some landslide deposits in these shadowed areas may not have been identified, (3) small or shallow landslide deposits in the higher parts of the map area, covered by thick forest, may not have been recognized, (4) older 

landslide deposits whose original topography has been extensively modified by erosion may not have been identified, and (5) various types of mass movement deposits are clearly underrepresented on this map. Because of the small scale of the map, talus and debris flow deposits are not shown.

This map has been prepared to provide a regional overview of the distribution of landslide 

deposits in the Los Alamos 30′ × 60′ quadrangle, and as such constitutes an inventory of landslides in 

the area. The map is suitable for regional planning to identify broad areas where landslide deposits and processes are concentrated. It should not be used as a substitute for detailed site investigations. Specific areas thought to be subject to landslide hazards should be carefully studied before development. S.L. Reneau and other investigators from Los Alamos National Laboratory have discussed landslides and rates of slope retreat with respect to environmental remediation work (for example, Reneau and others,1995). Additional studies are described in the 1996 New Mexico Geological Society field trip guidebook to the Jemez Mountains (Goff and others, 1996).

SELECTED REFERENCES

Brabb, E.E., Guzzetti, F., Mark, R.K., and Simpson, R.W., Jr., 1989, The extent of landsliding in 

northern New Mexico and similar semi-arid and arid regions, in Sadler, P.M., and Morton, D.M., 

eds., Landslides in a semi-arid environment: Inland Geological Society, v. 2, p. 163–173.

Cardinali, M., Guzzetti, F., and Brabb, E.E., 1990, Preliminary maps showing landslide deposits and 

related features in New Mexico: U.S. Geological Survey Open-File Report 90–293, 4 sheets, scale 1:500,000.

Dethier, D.P., 1997, Geology of White Rock quadrangle, Los Alamos and Santa Fe Counties, New 

Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 73, scale 1:24,000.

Dethier, D.P., and Reneau, S.L., 1996, Lacustrine chronology links late Pleistocene climate change 

and mass movements in northern New Mexico: Geology, v. 24, p. 539–542.

Gardner, J.N., and Goff, F., 1996, Geology of the northern Valles Caldera and Toledo embayment, 

New Mexico: New Mexico Society Guidebook, 47th Field Conference, Jemez Mountains Region, p. 225–230.

Goff, F., Gardner, J.N., Baldridge, W.S., Hulen, J.B., Nielson, D.L., Vaniman, D., Heiken, G., 

Dungan, M.A., and Broxton, D., 1989, Volcanic and hydrothermal evolution of Valles caldera and Jemez volcanic field: New Mexico Bureau of Mines and Mineral Resources, Memoir 46, Excursion 17B, p. 381–434.

Goff, F., Gardner, J.N., and Valentine, G., 1990, Geology of St. Peter’s Dome area, Jemez 

Mountains, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 69, scale 1:24,000.

Goff, F., Kues, B.S., Rogers, M.A., McFadden, L.D., and Gardner, J.N., eds.,1996, The Jemez 

Mountain Region: New Mexico Geological Society Guidebook no. 47, 484 p.

Kelley, V.C., 1977, Geology of Albuquerque Basin, New Mexico: New Mexico Bureau of Mines and 

Mineral Resources, Memoir 33, 59 p. (geologic map in pocket, scale 1:190,000).

——1978, Geology of Española Basin, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources, Geologic Map 48, scale 1:125,000.

Olig, S.S., Kelson, K.I., Gardner, J.N., Reneau, S.L., and Hemphill-Haley, M., 1996, The earthquake 

potential of the Pajarito fault system: New Mexico Geological Society Guidebook, 47th Field Conference, Jemez Mountain Region, p. 143–152.

Reneau, S.L., and Dethier, D.P., 1996a, Late Pleistocene landslide-dammed lakes along the Rio 

Grande, White Rock Canyon, New Mexico: Geological Society of America Bulletin, v. 108, p. 1492–1507.

——1996b, Pliocene and Quaternary history of the Rio Grande, White Rock Canyon and vinicity, 

New Mexico: New Mexico Geological Society Guidebook, 47th Field Conference, Jemez Mountain Region, p. 317–324.

Reneau, S.L., Dethier, D.P., and Carney, J.S., 1995, Landslides and other mass movements near 

Technical Area 33, Los Alamos National Laboratory: Los Alamos National Laboratory Report LA-12955-MS, 48 p.

Reneau, S.L., Gardner, J.N., and Forman, S.L., 1996, New evidence for the age of the youngest 

eruptions in the Valles caldera, New Mexico: Geology, v. 24, p. 7–10.

Smith, G.A., and Kuhle, A.J., 1998a, Geologic map of the Santo Domingo Pueblo quadrangle, 

Sandoval County, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Open-file Digital Geologic Map OFDM 15, scale 1:24,000.

——1998b, Geologic map of the Santo Domingo Pueblo Southwest quadrangle, Sandoval County, 

New Mexico: New Mexico Bureau of Mines and Mineral Resources, Open-file Digital Geologic Map OFDM 26, scale 1:24,000.

Smith, R.L., Bailey, R.A., and Ross, C.S., 1970, Geologic map of the Jemez Mountains, New 

Mexico: U.S. Geological Survey Miscellaneous Investigations Series Map I–571, scale 1:125,000.

Varnes, D.J., 1978, Slope movement types and processes, in Schuster, R.L., and Krizek, R.J., eds., 

Landslides; analysis and control: Transportation Research Board Special Report 176, p. 12–33.

Woodward, L.A., 1987, Geology and mineral resources of Sierra Nacimiento and vicinity, New 

Mexico: New Mexico Bureau of Mines and Mineral Resources, Memoir 42, 85 p. (geologic map in pocket, scale 1:100,000).

Woodward, L.A., Anderson, J.B., Kaufman, W.H., and Reed, R.K., 1973, Geologic map and 

sections of San Pablo Quadrangle, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 26, scale 1:24,000.

Woodward, L.A., DuChene, H.R., and Martinez, R., 1977, Geology of Gilman Quadrangle, New 

Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 45, scale 1:24,000.

Woodward, L.A., DuChene, H.R., and Reed, R.K., 1974, Geologic map and sections of San Miguel 

Mountain Quadrangle, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 33, scale 1:24,000.

Woodward, L.A., Kaufman, W.H., and Reed, R.K., 1973, Geologic map and sections of Rancho del 

Chaparral Quadrangle, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 27, scale 1:24,000.

Woodward, L.A., and Martinez, R., 1974, Geologic map and sections of Holy Ghost Quadrangle, 

New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 33, scale 1:24,000.

Woodward, L.A., and Ruetschilling, R.L., 1976, Geology of San Ysidro Quadrangle, New Mexico: 

New Mexico Bureau of Mines and Mineral Resources, Geologic Map 37, scale 1:24,000.

Woodward, L.A., and Schumacher O.L., 1973, Geologic map and sections of La Ventana 

Quadrangle, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 28, scale 1:24,000.

MISCELLANEOUS FIELD STUDIES

MAP MF–2328

Any use of trade names in this publication is fordescriptive purposes only and does not imply endorsement by the U.S. Geological SurveyThis map was produced on request, directly fromdigital files, on an electronic plotterFor sale by U.S. Geological Survey Information ServicesBox 25286, Federal Center, Denver, CO 802251-888-ASK-USGSThis map is also available as a PDF at http://greenwood.cr.usgs.gov

PRELIMINARY MAP OF LANDSLIDE DEPOSITS IN THE LOS ALAMOS 30′ × 60′ QUADRANGLE, NEW MEXICO

By

P.E. Carrara1 and D.P. Dethier2

1999

Geology mapped by P.E. Carrara, July–September 1997.

Manuscript approved for publication August 27, 1999

1 0 1 2 3 4 5 6 7 8 9 10 KILOMETERS

SCALE 1:100 000

1 0 1 2 3 4 5 6 7 8 MILES

CONTOUR INTERVAL 50 METERS

NATIONAL GEODETIC VERTICAL DATUM OF 1929

NEW MEXICO

QUADRANGLE LOCATION

12°

APPROXIMATE MEAN

DECLINATION, 1978

TRUE NORTH

MAG

N

ETIC NO

RTH

1U.S. Geological Survey, Denver, Colo.2Department of Geosciences, Williams College, Williamstown, Mass.

152119

6

181716

20

4

3

13

14

11 12b 12a

10

5

8

7

12c

9

INDEX MAP SHOWING SOURCES OF GEOLOGIC DATA

[Sources 1 and 2 encompass entire quadrangle]

SOURCES OF GEOLOGIC DATA

1. Cardinali and others (1990); Kelley, (1977, 1978).2. Carrara, P.E., unpublished reconnaissance surficial geologic mapping, scale 1:100,000; Kelley, (1977, 1978).3. Dethier, (1997).4. Dethier, D.P., unpublished geologic mapping, scale 1:24,000, 1998.5. Dethier, D.P., and Thompson, R.A., unpublished geologic mapping, scale 1:24,000, 1998.6. Formento-Trigilio, M.L., unpublished geologic mapping, scale 1:24,000, 1997.7. Gardner and Goff, (1996).8. Goff and others, (1990).9. Pazzaglia, F.J., unpublished geologic mapping, scale 1:24,000, 1997.

10. Reneau and others, (1995).11. Sawyer, D.A., Shroba, R.R., Minor, S.A., Thompson, R.A., and Blossom, J.C., unpublished geologic mapping, scale 

1:24,000, 1998–1999.

12a. Smith and Kuhle, (1998a).12b. Smith and Kuhle, (1998b).12c. Smith, G.A. and Kuhle, A.J., unpublished geologic mapping, scale 1:24,000, 1997–1998.

13. Smith and others, (1970).14. Thompson, R.A., and Shroba, R.R., unpublished geologic mapping, scale 1:24,000, 1998, 1999.15. Woodward, Anderson, and others (1973).16. Woodward and others (1977).17. Woodward and others (1974).18. Woodward, Kaufman, and Reed (1973).19. Woodward and Martinez (1974).20. Woodward and Ruetschilling (1976).21. Woodward and Schumacher (1973).

107°00′ 106°00′

36°00′35°30′

13