Virgin Islands National Park 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/226 

National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 
THIS PAGE: 

Underwater ecosystems including coral reefs 

are a primary natural resource at Virgin

Islands National Park. National Park Service 

photograph.

ON THE COVER:

This view of Trunk Bay shows the steep 

slopes characteristic of Virgin Islands National Park. National Park Service photograph courtesy Rafe Boulon (Virgin Islands 

National Park).
Virgin Islands National Park 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/226 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 

July 2010 

U.S. Department of the Interior 

National Park Service 

Natural Resource Program Center 

Fort Collins, Colorado
The National Park Service, Natural Resource Program Center publishes a range of reports that 

address natural resource topics 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 high-priority, current natural 

resource management information with managerial application. The series targets a general, 

diverse audience, and may contain NPS policy considerations or address sensitive issues of 

management applicability. 

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. 

Printed copies of this report are produced in a limited quantity and they are only available as 

long as the supply lasts. This report is available from the Geologic Resources Inventory website 

(http://www.nature.nps.gov/geology/inventory/gre_publications.cfm) and the Natural 

Resource Publications Management website (http://www.nature.nps.gov/publications/

NRPM). 

Please cite this publication as: 

Hall, K. and K. KellerLynn. 2010. Virgin Islands National Park: geologic resources inventory 

report. Natural Resource Report NPS/NRPC/GRD/NRR—2010/226. National Park Service, 

Fort Collins, Colorado. 

NPS 161/104872, July 2010 

ii NPS Geologic Resources Division 
VIIS Geologic Resources Inventory Report iii

Contents

List of Figures................................................................................................................ iv

Executive Summary ....................................................................................................... v

Acknowledgements...................................................................................................... vi

Credits........................................................................................................................................................................ vi

Introduction ................................................................................................................... 1

Purpose of the Geologic Resources Inventory ...............................................................................................................1

Park Setting .................................................................................................................................................................1

Geologic Issues .............................................................................................................. 5

Slope Stability and Erosion ...........................................................................................................................................5

Windblown Dust..........................................................................................................................................................5

Sea Level Rise...............................................................................................................................................................6

Anthropogenic Modifications.......................................................................................................................................6

Recreational Impacts....................................................................................................................................................6

Benthic Habitat Mapping .............................................................................................................................................7

Geologic Features and Processes................................................................................ 10

Beach Types...............................................................................................................................................................10

Coastal Sediments......................................................................................................................................................10

Coral Reefs ................................................................................................................................................................10

Igneous and Volcanic Features and Processes.............................................................................................................10

Salt Ponds..................................................................................................................................................................11

Seismic Activity ..........................................................................................................................................................12

Paleontological Resources ..........................................................................................................................................12

Map Unit Properties .................................................................................................... 19

Geologic History .......................................................................................................... 23

Lameshur Volcanic-Intrusive Complex.........................................................................................................................23

Louisehoj Formation...................................................................................................................................................23

Outer Brass Limestone ...............................................................................................................................................23

Tutu Formation..........................................................................................................................................................23

Dikes, Narrows Pluton, and Virgin Gorda Batholith.....................................................................................................24

Surficial Deposits........................................................................................................................................................24

Glossary........................................................................................................................ 25

Literature Cited............................................................................................................ 28

Additional References ................................................................................................. 31

Appendix A: Overview of Digital Geologic Data....................................................... 32

Appendix B: Scoping Meeting Participants................................................................ 35

Attachment 1: Geologic Resources Inventory Products CD
iv NPS Geologic Resources Division

List of Figures

Figure 1. Map of Virgin Islands National Park, St. John, U.S. Virgin Islands........................................................................3

Figure 2. Tectonic map of the Caribbean plate .................................................................................................................4

Figure 3. Seismicity map of Central America and the Caribbean........................................................................................4

Figure 4. Rockslide...........................................................................................................................................................7

Figure 5. Relative coastal vulnerability ..............................................................................................................................8

Figure 6. Geomorphologic areas......................................................................................................................................9

Figure 7. Cobbles and beachrock ...................................................................................................................................13

Figure 8. Cobblestone beach .........................................................................................................................................13

Figure 9. Rocky shoreline ...............................................................................................................................................14

Figure 10. Elkhorn coral.................................................................................................................................................14

Figure 11. Columnar jointing .........................................................................................................................................15

Figure 12. White Cliffs...................................................................................................................................................15

Figure 13. Pillow basalt..................................................................................................................................................16

Figure 14. Metamorphosed and interlayered sandstone and shale..................................................................................16

Figure 15. Salt ponds.....................................................................................................................................................17

Figure 16. Geologic timescale ........................................................................................................................................18

Figure 17. Taino trading bead........................................................................................................................................24

Figure 18. Marble..........................................................................................................................................................24
VIIS Geologic Resources Inventory Report v

Executive Summary

This report accompanies the digital geologic map for Virgin Islands National Park in St. 

John, U.S. Virgin Islands, produced by the Geologic Resources Division in collaboration 

with its partners. It contains information relevant to resource management and scientific 

research. This document incorporates preexisting geologic information and does not include 

new data or additional fieldwork.

Virgin Islands National Park is world-renowned for its 

pristine beaches, clear turquoise waters, and remarkable 

natural and cultural resources. The park is home to a vast 

array of ecosystems, including coral reefs, mangrove 

forests, salt ponds, sea grass beds, subtropical forests, dry 

forests, and sandy (and “rocky”) beaches. 

Virgin Islands National Park is located primarily on the 

island of St. John in the Caribbean Sea. Virgin Islands 

Coral Reef National Monument, established in 2001,

encompasses 5,143 ha (12,708 ac) of submerged lands 

adjacent to St. John.

More than 100 million years ago, complex geologic 

processes began forming the setting of Virgin Islands 

National Park. Many of the important resource-related

issues currently faced by park managers are connected to 

past and ongoing geologic and hydrologic features and 

processes. A variety of physical processes such as 

seismicity, slope stability, oceanographic variables, and 

climatic conditions can drastically alter the landscape. 

Geology also plays a significant role in the protection and 

preservation of biological and cultural resources. Thus, a

general knowledge of the geologic resources within the 

park is crucial for effective park management, scientific 

research, and interpretation. 

Virgin Islands National Park is an ideal venue for 

studying the links between geologic, biologic, and 

cultural resources. Park visitors are afforded an 

exceptional opportunity to learn about the park’s 

geologic resources during interpretive hikes and talks.

The rich landscape provides a fitting backdrop for

discussing the geologic history of the area and its 

ongoing physical processes, which continue to alter the 

landscape yearly, seasonally, and even daily.

The following geologic issues, features, and processes are 

of primary importance and have the highest level of 

management significance to Virgin Islands National 

Park:

• Slope stability and erosion. The park is characterized 

by rugged terrain and steep, rocky slopes. More than 

three-quarters of St. John is covered with hillsides in 

excess of 30% slope. Slope failure is common during 

storm events and can devastate terrestrial, coastal, and 

marine habitats. In addition, rockfalls and mudslides

can pose serious hazards to park visitors and 

infrastructure (including roads, which can be rendered 

impassable). Unpaved roads throughout the park are 

easily eroded, creating an additional management 

concern. Grazing is another cause of slope failure; feral 

animals such as goats and hogs heavily graze on steep 

hillsides within the park, increasing erosion and 

sedimentation into adjacent coastal and marine 

ecosystems. Even small increases in sediment supply 

can have devastating effects on fragile environments 

such as coral reefs and sea grass beds. 

• Windblown contaminants. Park employees are

investigating the effects of dust particulates on park 

resources. Findings suggest that imported particulates, 

primarily from Africa, carry dust-borne pathogens that 

can harm fragile marine habitats such as coral reefs 

and sea grass beds. Dust from alternate sources (e.g., 

ash fall from the 1995 Montserrat eruption) could also 

negatively impact these habitats.

• Coastal features and processes. The park is known for 

its beautiful beaches and unique coastal ecosystems; 

thus, the protection and preservation of these valuable 

resources is a primary concern. Many of the threats to 

these resources result from visitor use and human 

activities, but also from natural coastal dynamics. 

Immediate management concerns include beach 

erosion, sea level rise, anthropogenic modifications, 

and salt pond infilling.

• Marine features and processes. Participants at the 2004 

scoping meeting identified a need for additional 

marine mapping products—in particular, mapping that 

targets geologic features and processes such as 

sediment characteristics, oceanographic variables, and 

benthic habitats. Monitoring of recreational impacts 

from boating and surfing would also help to minimize 

detrimental effects on marine resources. 

The glossary contains explanations of many technical 

terms used in this report, including terms used in the 

Map Unit Properties Table. A geologic time scale is 

provided as figure 16.
vi NPS Geologic Resources Division 

Acknowledgements 

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

Park Service Inventory and Monitoring Program. The GRI is administered by the 

Geologic Resources Division of the Natural Resource Program Center. 

The Geologic Resources Division relies heavily on 

partnerships with institutions such as the U.S. 

Geological Survey, Colorado State University, state 

geologic surveys, local museums, and universities in 

developing GRI products. 

Special thanks to Rafe Boulon (Virgin Islands 

National Park) who provided additional information 

and many photographs used in the report. 

Credits 

Authors 

Kim Hall (NPS Geologic Resources Division) 

Katie KellerLynn (Colorado State University) 

Review 

Douglas Rankin (U.S. Geological Survey) 

Bruce Heise (NPS Geologic Resources Division) 

Editing 

Bonnie Dash (Envirocal) 

Digital Geologic Data Production 

Georgia Hybels (NPS Geologic Resources Division) 

Stephanie O’Meara (Colorado State University) 

Digital Geologic Data Overview Layout Design 

Phil Reiker (NPS Geologic Resources Division) 

John Gilbert (Colorado State University) 
VIIS Geologic Resources Inventory Report 1

Introduction

The following section briefly describes the National Park Service Geologic Resources 

Inventory and park setting of Virgin Islands National Park.

Purpose of the Geologic Resources Inventory 

The Geologic Resources Inventory (GRI) is one of 12 

inventories funded by the National Park Service (NPS) 

Inventory and Monitoring Program. The GRI, 

administered by the Geologic Resources Division of the 

Natural Resource Program Center, is designed to 

provide and enhance baseline information available to 

park managers. The GRI team relies heavily on 

partnerships with institutions such as the U.S. Geological 

Survey, Colorado State University, state geologic surveys, 

local museums, and universities in developing GRI 

products.

The goals of the GRI are to increase understanding of the 

geologic processes at work in parks and to provide sound 

geologic information for use in park decision making. 

Sound park stewardship requires an understanding of 

the natural resources and their role in the ecosystem. 

Park ecosystems are fundamentally shaped by geology. 

The compilation and use of natural resource information 

by park managers is called for in section 204 of the 

National Parks Omnibus Management Act of 1998 and in 

NPS-75, Natural Resources Inventory and Monitoring 

Guideline. 

To realize these goals, the GRI team is systematically 

conducting a scoping meeting for each of the 270 

identified natural area parks and providing a parkspecific digital geologic map and geologic report. These 

products support the stewardship of park resources and 

are designed for nongeoscientists. Scoping meetings 

bring together park staff and geologic experts to review 

available geologic maps and discuss specific geologic 

issues, features, and processes. 

The GRI mapping team converts the geologic maps 

identified for park use at the scoping meeting into digital 

geologic data in accordance with their Geographic 

Information Systems (GIS) Data Model. These digital 

data sets bring an interactive dimension to traditional 

paper maps. The digital data sets provide geologic data 

for use in park GIS and facilitate the incorporation of 

geologic considerations into a wide range of resource 

management applications. The newest maps contain 

interactive help files. This geologic report assists park 

managers in the use of the map and provides an overview 

of park geology and geologic resource management 

issues.

For additional information regarding the content of this 

report and current GRI contact information please refer 

to the Geologic Resources Inventory web site 

(http://www.nature.nps.gov/geology/inventory/).

Park Setting

The Virgin Islands are situated at the northern end of the 

Lesser Antilles island chain. The Lesser Antilles are one 

of three island groups in the Caribbean Sea, along with 

the Greater Antilles and the Bahamas.

The U.S. Virgin Islands are composed of three primary 

islands—St. Thomas, St. John, and St. Croix—and several 

smaller surrounding islands. St. Croix has the largest land 

mass, at 207 km2 (80 mi2), and a relatively high western 

mountainous tip. St. Croix features coral growth along 

much of its insular shelf. St. Thomas is the second largest

of the U.S. Virgin Islands, at 83 km2 (32 mi2). St. John is 

the smallest, at 52 km2 (20 mi2) (Turgeon et al. 2002).

Virgin Islands National Park covers much of the island of 

St. John, the least developed of the three main U.S. Virgin 

Islands (fig. 1). The park envelopes 3,893 ha (9,620 ac) in 

its entirety—including more than three-quarters of St. 

John, part of St. Thomas, part of the smaller Hassel 

Island, and 229 ha (5,650 ac) of underwater marine area.

Steep rocky slopes, many in excess of 30%, characterize 

St. John. The highest peaks on the island are Camelberg 

Peak (364 m [1,193 ft]) and Bordeaux Mountain (389 m

[1,277 ft]) (fig. 1). The northern slopes of St. John are 

covered in moist subtropical forests, while dry forests 

characterize the south and east sides of the island. 

Fringing coral reefs and sea grass beds surround the 

island. 

Because of its incredible array of water resources, land 

resources, and biodiversity, in 1976, the United Nations 

declared Virgin Islands National Park a biosphere 

reserve. This designation is recognized under the United 

Nations Educational, Scientific, and Cultural 

Organization (UNESCO) Man and the Biosphere 

Program. The biosphere reserve serves as a “living 

laboratory,” utilizing an integrative approach to the 

responsible management of natural resources while 

promoting sustainable economic and human 

development (UNESCO 2000).

The establishment of Virgin Islands Coral Reef National 

Monument in 2001 added 5,143 ha (12,708 ac) of 

submerged land to the National Park System, and

approximately doubled the amount of acreage in and 

around St. John under NPS stewardship. 

Cultural History 

St. John’s cultural history is colorful and complex, with 

the first humans arriving in 1000 BCE (Before Common 

Era). The first village settlements developed from 200 

BCE to CE 600 (Common Era), with rapid population 

growth and village expansion across the landscape 

between 600 and 1200. Between 1200 and 1492, the 

Taino culture developed. Living within the sheltered 
2 NPS Geologic Resources Division

bays of the island, the Taino people practiced agriculture, 

introducing nonnative foods such as manioc (cassava) to 

the island. They also hunted and gathered food from 

primarily marine resources. For unknown reasons, the 

Taino vanished from the island before 1492 (Zanhniser 

1999). Archaeological sites associated with the Taino 

culture, as well as Danish occupation (1718–1850) and 

African-slave communities, are contained within Virgin 

Islands National Park. Many sites on St. John are listed in 

the National Register of Historic Places. 

Following the Taino, human habitation on St. John 

existed as follows:

• 1450 to 1550—Contact between Taino and Carib 

cultures, followed by Spanish and the demise of preColumbian culture

• 1580 to 1700—European expansion into the Caribbean 

and the age of Piracy and Privateers 

• 1665 to 1733—Early European settlement of St. 

Thomas/Hassel Island and St. John

• 1733 to 1840s—Expansion of sugar, cotton, slavery,

and maritime commerce

• 1801 to 1815—The Napoleonic War and British 

occupation

• 1839 to 1848—Underground Railway period marked 

by guardhouses and escape routes

• 1840s to 1917—Emancipation, signaling the end of the 

sugar and cotton industry and the introduction of bay 

rum, cattle, and charcoal production during a new era 

of maritime commercial expansion (National Park 

Service 2010a).

In 1917, the United States purchased the Virgin Islands 

from Denmark, beginning the American “Naval Regime” 

(with military installations on Hassel Island) and

continuing through World War II. Starting in the 1920s,

tourism blossomed as visitors from the United States 

began to discover and move to the Virgin Islands. In the 

1950s, tourism became the islands’ major source of 

commerce and industry. Nearly 416,000 people visited 

Virgin Islands National Park in 2009. The community of 

St. John strives to balance the demands of tourism and 

economic growth while preserving this Caribbean 

paradise. 

Establishment of Virgin Islands National Park 

On August 2, 1956, President Eisenhower signed a bill 

that established Virgin Islands National Park. The 

creation of the park was in large part due to a generous 

donation by Laurence S. Rockefeller, who witnessed the 

beauty of St. John during a Caribbean cruise in the 1950s. 

Rockefeller and his family acquired more than 2,000 ha 

(5,000 ac) on St. John with the intention of preserving the 

pristine and untamed beauty of the area. Rockefeller

donated more than half of the initial acreage of the park,

including the acquisition of private inholdings, as they 

become available (Rockefeller Archive Center 2004).

Establishment of Virgin Islands Coral Reef National Monument

On January 17, 2001, President Clinton proclaimed

Virgin Islands Coral Reef National Monument to protect 

and preserve the delicate coral resources. The

monument encompasses submerged lands adjacent to St.

John, including Hurricane Hole, a well-developed 

tropical marine ecosystem. On July 20, 2002, NPS 

Director Mainella stated before the Subcommittee on 

National Parks, Recreation and Public Lands that the 

monument should “provide for a recovery of coral reefs 

and associated habitats, facilitate an increase in the 

abundance of reef fish, sustain traditional cultural fishing 

practices in surrounding waters, enhance the quality of 

the visitor experience to the Virgin Islands, and 

contribute to economic growth from tourism” (Mainella 

2002).

Geologic Setting

The Virgin Islands and Virgin Islands National Park are 

geographically part of the Lesser Antilles but are more 

akin geologically with the Greater Antilles (Rankin 2002). 

The Greater Antilles, which rise from a marine plateau,

include Cuba, Hispaniola (Haiti and the Dominican 

Republic), Jamaica, and Puerto Rico. The Greater 

Antilles are situated along the northern margin of the 

Caribbean tectonic plate (fig. 2), which is moving 

eastward at about 2 cm (0.8 in) per year with respect to 

both the North American and South American plates. 

The Caribbean plate is bounded on the north by a leftlateral, strike-slip fault, and on the south by a rightlateral, strike-slip fault. The eastern boundary of the 

Caribbean plate is a subduction zone, where oceanic 

crust under the Atlantic Oceans is being forced beneath

oceanic crust beneath the Caribbean Sea. This 

subduction zone fuels the volcanoes of the Lesser 

Antilles, such as the Soufriere Hills volcano that has 

buried much of Montserrat beginning in the mid 1990s. 

Volcanic activity occurs as far north as the island of Saba 

about 160 km (100 mi) southeast of St. John (Rankin 

2002). St. John is in the northeastern corner of the 

Caribbean plate where motion on the plate boundary is 

transitional from subduction to strike-slip. Plate 

boundaries are seismically active (fig. 3) with the 

potential for large earthquakes in the Caribbean as 

evidenced by the January 12, 2010 earthquake that 

devastated Haiti. 

The Greater Antilles are part of an older subductionrelated magmatic arc, most likely built on oceanic crust 

beginning in the Lower Cretaceous Period and lasting 

through the Eocene Epoch (Pindell and Barrett 1990; 

Rankin 2002) (see fig. 16 for a geologic time scale). The

arc hosts two distinct magmatic series. The oldest rocks 

formed in an extensional (Earth’s crust pulling apart) 

environment, and include keratophyre (sodium-rich 

rhyolite lava), basalt, and sheeted dikes. The character of 

the volcanism changed after deposition of the Water 

Island Formation (see Map Unit Properties Table) to the 

more typical island-arc volcanism represented on St. 

John by andesite and basalt in the Louisenhoj and Tutu 

formations.
VIIS Geologic Resources Inventory Report 3Figure 1. Map of Virgin Islands National Park, St. John, U.S. Virgin Islands. National Park Service map. 
4 NPS Geologic Resources Division

Figure 2. Tectonic map of the Caribbean plate. The Virgin Islands are situated along a zone of left-lateral, strike-slip faults that define the 

plate boundary between the Caribbean and North American plates. The eastern margin of the Caribbean plate is a subduction zone. The 

southern and northern margins are transform faults. From ESRI Arc Image Service USA Prime Imagery, compiled by Jason Kenworthy (NPS 

Geologic Resources Division). Plate boundaries after Lillie (2005).

Figure 3. Seismicity map of Central America and the Caribbean. Recorded seismic activity outlines the boundary of the oval-shaped Caribbean 

plate. Colored dots on the figure record 16 years (1990–2006) of earthquakes and their depths. The orange star indicates the location of the 

January 12, 2010, earthquake in Haiti. Yellow lines show plate boundaries. Modified from U.S. Geological Survey (2009) by Jason Kenworthy 

(NPS Geologic Resources Division).
VIIS Geologic Resources Inventory Report 5

Geologic Issues

The Geologic Resources Division held a Geologic Resources Inventory scoping session for 

Virgin Islands National Park on April 7–9, 2004, to discuss geologic resources, address the 

status of geologic mapping, and assess resource management issues and needs. This section

synthesizes the scoping results, in particular those issues that may require attention from 

resource managers. Contact the Geologic Resources Division for technical assistance.

Slope Stability and Erosion

St. John is characterized by rugged terrain and steep 

rocky slopes. More than 80% of the island is covered 

with hillsides in excess of 30% (CH2M Hill 1979). 

Runoff and slope failure are common during storm 

events, and can impact the park’s terrestrial, coastal, and 

marine habitats. Slope failure—caused by a variety of 

factors, including climatic conditions, geologic 

processes, and anthropogenic modification to the 

landscape—can pose serious hazards to park visitors, 

employees, and infrastructure. Wieczorek and Snyder 

(2009) suggest methodology for monitoring slope 

movements.

Severe storm events and seismic activity cause rockslides 

and rockfalls within the park (fig. 4). In turn, these 

processes can severely impact federally protected 

species. During Tropical Storm Frances (2002), unstable 

slopes decimated numerous nesting sites of the 

endangered brown pelican (Pelecanus occidentalis). In 

addition, roads are often impassable during storm events 

because of rockslides and mudslides. During and after 

severe storms in 2003, mud and hillside debris, some as 

much as 4 m (12 ft) thick, made road travel impossible in 

parts of the park. More recent storms have caused less 

damage. In 2007, Tropical Storm Olga passed 6 km (4 mi) 

from St. John, with maximum sustained winds of only 40 

mph (65 kph) and caused minor impacts (Zengerle 2007; 

Caribbean Hurricane Network 2009). In 2008, Hurricane 

Omar passed 79 km (49 mi) from St. John, and the island 

escaped significant damage (Burnett 2008; Caribbean 

Hurricane Network 2009).

Overgrazing also causes slope failure. A variety of 

nonnative species (e.g., hogs, goats, and donkeys) have 

been introduced to the island of St. John, and many of 

these animals have escaped or have been released into 

park boundaries. These invasive animals have created 

large feral populations that exacerbate sedimentation 

rates within the park. Feral animals graze heavily on 

native vegetation, which is an important sediment 

retainer; thus, a decrease in vegetation promotes an 

increase in localized sedimentation rates. Heavy grazing 

on steep hillsides increases erosion into adjacent coastal 

and marine ecosystems. Even small increases in 

sedimentation can have devastating effects on sensitive 

environments such as coral reefs and sea grass beds. 

The National Park Service is currently working in 

cooperation with non-profit organizations and 

numerous federal, state, and territorial agencies to safely 

and humanely reduce the number of feral animals within 

the boundaries of Virgin Islands National Park (National 

Park Service 2010b).

Coastal erosion may also threaten infrastructure on the 

island. In 2005, the NPS Geologic Resources Division 

responded to a technical assistance request regarding 

erosion impacts for a structure along Maho Bay (Beavers 

2005). Due to large cracks in the walls, a non-historic 

portion of the structure is slated for demolition, pending 

funding (R. Boulon, Virgin Islands National Park, 

personal communication, July 15, 2010). Beavers (2005) 

provided guidance and recommendations for installation 

of erosion control structures. However, erosion at the 

site appears to have stabilized and erosion control 

structures have not yet been constructed (R. Boulon, 

Virgin Islands National Park, personal communication, 

July 15, 2010).

Windblown Dust

The U.S. Geological Survey estimates that eolian 

processes transport several hundred million tons of dust 

yearly from western Africa into the Caribbean basin and 

the southeastern United States. African dust storms 

travel quickly across the Atlantic Ocean at altitudes as 

high as 4,570 m (15,000 ft). The intercontinental journey, 

which transports a wide variety of particulates and

organisms, takes approximately 5 to 7 days to complete 

(Kellogg and Griffin 2003). Dust particulates can harbor 

a wide spectrum of toxic substances, nutrients, organic 

pollutants, hydrocarbons, and polychlorinated 

biphenyls. In addition, African dust carries a high 

percentage of microbes, including bacteria, fungi, and 

viruses, which may have a detrimental effect on 

ecosystem health. Many of the microbes carried within 

the windblown particulates are destroyed by ultraviolet 

radiation; however, as many as 100 microbes per gram of 

soil survive the journey. During dust pulses, air samples 

contain 3 to 10 times more microbes than normal levels 

in the Virgin Islands (Kellogg and Griffin 2003); 

approximately 30% of these microbes are pathogenic 

and are potentially dangerous to people and the 

environment (Kellogg and Griffin 2003).

Recent studies show that African dust may be directly 

linked to the decline of many Caribbean marine species, 

including coral, sea fans, and sea urchins. Studies 

demonstrate a direct correlation between African dust 

pulses and marine ecosystem deterioration. Increased 

drought conditions in the Sahara and Sahel deserts since 

the 1970s correspond to increased disease and bleaching 

in Caribbean corals. In addition, Caribbean air samples 

contain many diseases such as the soil fungi Aspergillus. 
6 NPS Geologic Resources Division

One particular strain, Aspergillus sydowii, is directly 

responsible for the sea fan aspergillosis, which is a major 

Caribbean epizootic (similar to an “epidemic” in 

humans) (Kellogg and Griffin 2003).

The NPS Air Resources Division is an additional contact 

for technical assistance.

Sea Level Rise

The NPS Geologic Resources Division is working in 

conjunction with the U.S. Geological Survey and Woods 

Hole Oceanographic Institute to examine how future sea 

level rise will affect coastal areas within national parks. 

The Coastal Vulnerability Index (CVI) is a quantitative 

tool used by park managers and scientists to predict 

future changes to park shorelines (Pendleton et al. 2004). 

The geologic factors and physical processes considered 

in the CVI include relative sea level, wave height, tidal 

range, coastal erosion rate, slope, and geomorphology. 

Data collected at Charlotte Amalie on St. Thomas 

indicate a sea level rise of 0.5 ± 0.74 mm (0.02 ± 0.03 in) 

per year, wave heights from 1.0 to 1.9 m (3.3 to 6.2 ft), 

and a mean tidal range of 0.262 m (0.860 ft) at Virgin 

Islands National Park (Pendleton et al. 2004). As climate 

warms over the coming decades, globally averaged sea 

level may rise between 0.19 and 0.58 m (7.5 in and 1.9 ft) 

by 2100 (Meehl et al. 2007; Karl et al. 2009). The CVI 

indicates that 13% of the coast within Virgin Islands 

National Park is highly vulnerable to shoreline change 

resulting from future sea level rise. The research shows 

that Trunk Bay, Cinnamon Bay, and Ram Head are the 

beaches most likely to experience extreme shoreline 

change. In addition, the CVI designates 29% of the coast 

within the park as highly vulnerable, 28% as moderately 

vulnerable, and 29% as minimally vulnerable (fig. 5). 

As ranked by Pendleton et al. (2004), geomorphology, 

regional coastal slope, and wave energy are the most 

important variables in determining the spatial variability 

of the CVI for the park. Shoreline change rate, tidal 

range, and sea level rise rate do not contribute to the 

spatial variability in the CVI (Pendleton et al. 2004). 

Vulnerability based on geomorphology indicates that

sandy beach shoreline areas are very highly vulnerable to 

change, gravel beaches are highly vulnerable, alluvium or 

cliffs with fringing reefs are moderately vulnerable, and 

rock and cliff features are minimally vulnerable (fig. 6). 

In addition, areas of intense wave action—especially 

shorelines open to the Atlantic Ocean, such as the stretch 

from Hawksnest Bay to Cinnamon Bay—are more likely 

to experience change as compared to protected 

shorelines on the north side of St. John, such as Leinster 

Bay (Pendleton et al. 2004).

Anthropogenic Modifications

The National Park Service generally allows natural 

coastal processes to occur without interference; 

however, if natural processes threaten the preservation 

of cultural resources, park managers may elect to modify 

a shoreline in an attempt to achieve a balance between 

preserving a historic landmark and protecting a natural 

ecosystem. For example, managers at Virgin Islands 

National Park have modified some of the park’s 

shoreline to protect important cultural resources from 

coastal erosion and storm events. In the 1970s, the 

National Park Service placed riprap on Cinnamon Bay to 

protect Taino and Dutch archaeological sites. Although 

the riprap has slowed the rate of erosion, it has done little 

to diminish natural shoreline processes. The loss of 

adjacent shoreline vegetation, due to both erosion and 

recreational impacts, is another management concern. 

Structures such as docks and visitor facilities at 

Lameshur, Caneel, Cruz Bay, and Red Hook could alter 

hydrodynamics and affect shoreline geomorphology, and 

changes in sediment transport could lead to beach 

erosion or accretion. Beaches naturally migrate landward 

to compensate for sea level rise, and the presence of 

anthropogenic structures hinders this natural process, 

potentially causing catastrophic habitat loss. Monitoring 

changes in oceanographic variables (i.e., temperature, 

salinity, and current patterns) created by anthropogenic 

modifications could help in preventing the loss of natural 

resources. 

Dredging adjacent to park boundaries could cause 

significant impacts within the park as a result of changes 

to sediment transport and flow. Dredging is often 

conducted in Cruz Bay to benefit shipping, transport,

and recreation. Coastal dredging increases turbidity and 

sediment loads, thereby damaging marine resources. In 

addition, dredged sediments can contain contaminants 

and pollutants that are harmful to marine and coastal 

environments. 

Additional management concerns include the following:

(1) the detrimental effects of light pollution on sea turtle 

nesting patterns and hatchling emergence and (2) the 

rapid erosion rates of beaches at many visitor parking 

areas.

Recreational Impacts 

According to the NPS Public Use Statistics Office, a total 

of 7,608,944 people visited Virgin Islands National Park 

between 1998 and 2009 (National Park Service 2010c), 

and the recreational impacts from these visitors are

degrading natural resources. For example, recreational 

boating activities have damaged many fragile and 

cherished resources, such as coral reefs, sea grass beds, 

and mangrove forests. Although anchoring is permissible 

in certain areas of the park, illegal anchoring and anchor 

dragging can destroy marine habitat (Hall 2005). In 

addition, vessel groundings resulting from inexperienced 

boaters may critically damage large sections of coral reefs

(Hall 2005). Minor damage to the reef occurs when 

boats, unable to maneuver, run into the reef (Gladfelter 

et al. 1977).

The National Park Service has taken great strides to 

prevent anchor scouring of the seabed at Virgin Islands 

National Park and Virgin Islands Coral Reef National 

Monument. In 2000, park staff initiated a buoy program 

to aid in the recovery of the seafloor and to prevent 

future damage caused by boat anchoring and grounding. 

Park managers maintain more than 400 floating objects,
VIIS Geologic Resources Inventory Report 7

including overnight, day, scuba, and fishing moorings. 

This program has been highly successful, allowing sea

grass beds and mangroves to recover from previous 

damage. Investigators are analyzing data that will 

document recovery rates of sea grass in the park (Loomis 

2006).

Surfing is another concern for park resource managers

because it poses hazards to both visitors and resources. 

Recreational kite surfing is prohibited in boat exclusion 

areas and mooring areas (Chapter 1, Title 36, Code of 

Federal Regulations) but occurs at many park locations, 

including Johnson’s Reef, Fish Bay, and Cinnamon Bay.

Visitors have been critically injured while body surfing at 

Cinnamon Bay, which has a rapid change in beach slope

(K. N. Hall, written communication, November 2006). In 

addition to causing personal injuries, surfing can damage 

marine habitat when surfers brush up against fragile 

coral reefs.

Social trails near beaches are another management 

concern. Projects in the early 2000s along Trunk and 

Hawksnest beaches blocked off social trails which were 

revegetated with seagrapes (R. Boulon, Virgin Islands 

National Park, personal communication, July 15, 2010). 

Articulating ramps were installed to provide beach 

access.

Benthic Habitat Mapping

During GRI scoping in 2004, participants identified the 

need for coordination between the U.S. Geological 

Survey (USGS), National Oceanographic and 

Atmospheric Administration (NOAA), and the National 

Park Service in completing mapping of the benthic 

habitats at Virgin Islands National Park and Virgin 

Islands Coral Reef National Monument. Such mapping 

compliments the surficial and bedrock geology map of 

the park (see “Map Unit Properties” section and 

Appendix A). 

Through the implementation of a multi-year, interagency 

agreement between the National Park Service and the 

National Oceanic and Atmospheric Administration, 

NOAA’s Biogeography Branch mapped 53 km2 (20 mi2) 

of shallow-water habitats around St. John and 90 km2

(35mi2) of moderate-depth habitats south of St. John;

Zitello et al. (2009) mapped 32 distinct benthic habitat 

types within 12 zones. This effort is an expansion of 

ongoing mapping and monitoring in the U.S. Caribbean. 

The GIS products originating from this work include (1) 

accuracy assessment data, (2) ground validation data, (3) 

habitat maps, (4) source imagery, and (5) associated 

metadata. These data and accompanying reports, which 

describe the classification scheme, thematic accuracy, 

and methods used to create the maps, are available at 

http://ccma.nos.noaa.gov/ecosystems/coralreef/benthic_

usvi.html. 

Figure 4. Rockslide. Rockslides are common along the steep slopes of Virgin Islands National Park; this slide occurred near Hawksnest Bay. The 

disturbed area (lighter colors and debris at bottom of slope) is approximately 12 m (40 ft) tall, road cone for scale. National Park Service 

photograph by Rafe Boulon (Virgin Islands National Park).
8 NPS Geologic Resources Division A B DC E

H

Figure 5. Relative coastal vulnerability. This figure shows the relative coastal vulnerability index (CVI) and locations of geomorphologic features (see fig. 6) that investigators assessed for Virgin Islands National Park. The six variables assessed to determine the relative CVI are geomorphology, historical shoreline change rate, regional coastal slope, relative sea-level change, mean significant wave height, and mean tidal range. The photographs of locations A through H are presented in 

figure 6. U.S. Geological Survey graphic from Pendleton et al. (2004).

G

F
VIIS Geologic Resources Inventory Report 9

Figure 6. Geomorphologic areas. These different geomorphologic areas in Virgin Islands National Park were assessed as one of six variables 

that make up the coastal vulnerability index (CVI). See figure 5 for locations of photographs. (A) Trunk Bay from the east, very high 

vulnerability; (B) shoreline at Cinnamon Bay experiencing erosion, very high vulnerability; (C) Maho Bay from the east, very high 

vulnerability; (D) Mary Point, low vulnerability; (E) Annaberg Mill ruins in an area ranked as high vulnerability with respect to 

geomorphology; (F) shoreline surrounding Watermelon Bay (cobble beach), high vulnerability; (G) Ram Head (rocky headland), low 

vulnerability; and (H) White Cliffs near Reef Bay, low vulnerability. U.S. Geological Survey photographs, figure 5 in Pendleton et al. (2004).
10 NPS Geologic Resources Division

Geologic Features and Processes

This section describes the most prominent and distinctive geologic features and processes 

in Virgin Islands National Park.

Beach Types

The beaches of Virgin Islands National Park are worldrenowned. Factors such as bedrock composition, 

climate, and wave action create a diversity of beach types

within the park. Although the park is famous for its 

sandy beaches, the park shorelines are also adorned by 

areas of cobbles and beachrock (fig. 7), cobblestone (fig.

8), and steep rocky slopes (fig. 9).

Resistant igneous rock combined with high-energy wind 

and wave activity creates areas with a steep coastal 

profile. Easily eroded rock found in low-energy 

environments forms a gradual coastal profile. This 

creates the fine-grained sandy beaches at the park such 

as those at Trunk, Cinnamon, and Solomon bays. Sandy 

beaches are also formed in pockets between rocky 

headlands. These pockets are sheltered areas of reduced 

wave action. The fine-grained sandy beaches are almost 

all “coral” sands (Douglas W. Rankin, U.S. Geological 

Survey, written communication, January 22, 2010).

Cobble beaches commonly occur on the exposed 

southern and eastern shores of St. John, including Ram 

Head Point and Dittlif Point. A relatively dry climate, 

intense wave action, and hard bedrock define these 

areas. While hiking on Ram Head Trail, visitors can see a 

classic example of a cobble beach south of Salt Pond.

Coastal Sediments

Sediments that naturally supply the park’s shoreline are 

derived from a variety of terrestrial and marine sources 

(see Map Unit Properties Table). How quickly sediments 

weather and erode is strongly influenced by 

composition. For example, granitic rocks are less 

susceptible to erosion than those made of limestone.

Variations in chemical and mechanical weathering result 

in a variety of sediment sizes. In addition, wind and wave 

action influences sediment size and transport. Finer 

sediments such as the white sandy beaches at Trunk Bay 

need less energy for transport than the cobbles and 

pebbles on the beaches south of Saltpond Bay.

Longshore transport, one of the most important 

mechanisms for sediment movement and coastal change, 

is driven by waves that arrive at an angle to the coast. 

These waves force currents along the shore, carrying 

sediments. The sediment budget is the sum of the 

sediment supply (gains) and the sand removed (losses) 

from a system. Cumulative net loss is indicated by coastal 

erosion, whereas net growth is demonstrated by coastal 

expansion.

Coral Reefs

Caribbean coral reefs are one of the world’s most 

treasured marine resources. The brilliant blue waters at

Virgin Islands National Park are home to a wide variety

of corals, including elkhorn (Acropora palmata, fig. 10) 

and staghorn (Acropora cervicornis).

Coral reefs serve important geologic functions. During 

storm events and periods of high wave activity, coral 

reefs serve as a barrier against coastal erosion. They also 

act as an obstruction to reduce wave and wind impacts 

on inland environments. Elkhorn and staghorn corals 

have undergone particularly drastic decline in the past 30 

years, and in 2006 were the first coral species to be 

protected under the Endangered Species Act (Lundgren 

2008). Decline in coral has exposed shorelines to greater 

wave energies. 

In addition, coral reefs alter flow dynamics and initiate 

the deposition of fine-grained sediments on the 

downside of reefs. The reduction in suspended 

sediments helps to improve water quality in the 

surrounding waters. 

Igneous and Volcanic Features and Processes

Virgin Islands National Park hosts both volcanic and 

intrusive igneous rocks. These rocks display many 

distinctive features worthy of interpretation. 

Columnar Jointing

The Careen Hill Intrusive Suite contains many fine 

examples of columnar jointing—a geologic feature 

associated with the slow cooling and contraction of 

igneous rock. As magma of a tabular body (e.g., dike or 

sill) crystallizes and continues to cool, it contracts. 

Cooling cracks or joints develop perpendicular to the 

cooling surface (e.g., dike walls) and extend through the 

igneous body. The intersection of these fractures results 

in the formation of columns. Columnar joints generally 

develop a hexagonal pattern, but patterns of four, five, 

seven, or eight sides are also relatively common. This 

form of jointing develops in lava flows, sills, dikes, 

ignimbrites, and shallow intrusions of all compositions. 

Most columns are straight with parallel sides and 

diameters from a few centimeters to 3 m (10 ft).

A prime example of columnar jointing occurs on Leduck 

Island, located on the southeastern side of St. John 

adjacent to John’s Folly Beach (fig. 11). The columnar 

jointing on Leduck Island is composed of light-colored 

granitic rock called trondhjemite. The Water Island 

Formation hosts other examples of columnar jointing 

(see Map Unit Properties Table). 
VIIS Geologic Resources Inventory Report 11

Hydrothermal Alteration

Hydrothermal alteration created the beautifully colored 

(white, red, and brown) igneous rocks of south and 

central St. John. The presence of hot solutions—e.g., the 

fluids that generally accompany magmatic intrusions—

alter the chemical composition of the preexisting rocks, 

resulting in changes in mineralogy. The resulting rocks 

and colors have been further modified by modern 

weathering.

Hydrothermal alteration is evident in the Water Island 

Formation on St. John. The White Cliffs provide a 

beautiful example of this alteration (fig. 12).

Hydrothermal alteration includes the addition of water, 

silica, potassium, iron, and, in places, copper, sulfur, 

kaolinite, and limonite. The latter two minerals are, in 

part, also the product of recent oxidation and weathering 

of the already hydrothermally altered rocks; combined 

with alunite, they give the White Cliffs their distinctive 

white and red colors (Douglas W. Rankin, U.S. 

Geological Survey, written communication, January 22, 

2010).

Pillow Basalts

Pillow basalts are formed during the rapid underwater 

cooling of the surface of lava. The surface in contact with 

water cools quickly and forms a hard crust. Further 

cooling and contracting produces cracks through which 

still-molten lava emerges into the water in bulbous 

masses. These bulbous masses, called pillows, are quickly 

encased in a crust that itself cracks and allows the escape 

of another bulbous mass of lava. The result is layers and 

stacks of masses of pillows. In places, the rapid cooling 

causes shattering of the pillow, which results in rock 

composed of pillow fragments called hyaloclastite 

(Douglas W. Rankin, U.S. Geological Survey, written 

communication, January 22, 2010).

Most basalt in the Water Island Formation is pillow or 

hyaloclastite. Classic pillows occur to the west of Ram 

Head Trail, on Harbor Point, and on the peninsula of 

Turner Point (fig. 13). Because pillows are formed with 

the convex side up, geologists commonly use pillow 

basalt “bedding” to define a stratigraphic “way up.” 

Observations of the layering in pillow basalt and the way 

up have been helpful in working out the overall structure 

and stratigraphy of the Water Island Formation (Rankin 

2002).

Plutons 

Igneous intrusions called plutons form when molten 

magma cools and hardens underground. Size and 

mineral composition determine the specific type of 

pluton. The most common igneous intrusions located on 

and adjacent to the island of St. John are dikes, sills, and 

batholiths.

Dikes are small, tabular, intrusive bodies that form when 

magma is forced into fractures that cut across preexisting 

bedrock. The magma then cools and crystallizes, forming 

a dike. In many cases, a multitude of dikes form in a 

localized area, creating a “swarm.” Successive intrusions 

that lie adjacent and parallel to one another are “sheeted 

dikes.” Sheeted dikes are significant in that they indicate 

crustal extension—measured in miles—perpendicular to 

the walls of the dikes. The Tertiary (now officially called 

“Neogene;” International Commission on Stratigraphy 

2009) rocks of Virgin Islands National Park contain both 

dike swarms and sheeted dikes (see Map Unit Properties

Table).

Sills are another form of igneous intrusion common to St.

John. Sills are created when magma intrudes and hardens 

between preexisting rock layers. Similar to dikes, sills are 

tabular or sheetlike in shape, but form parallel to 

preexisting layering. Both dikes and sills are common 

features of the Careen Hill Intrusive Suite and intrude 

the Water Island Formation. In addition, excellent 

examples of dikes and sills occur within the Louisenhoj 

and Tutu formations. The dikes and sills are likely of 

more than one age.

A batholith is the largest type of igneous intrusion. This 

feature is formed by the slow underground cooling of a 

massive magma plume within the overlying country rock. 

The extreme temperature changes brought on by these 

large, molten rock bodies change the preexisting rock via 

the process of contact metamorphism. Through contact 

metamorphism, both the Narrows pluton and the Virgin 

Gorda batholith have transformed the surrounding rocks 

of northern St. John (see “Geologic History” section)—

portions of the Outer Brass Limestone have become 

marble; garnets are abundant in the Tutu Formation on 

Mary Point; and skarn has developed locally in the Tutu 

Formation (fig. 14).

Salt Ponds

Salt ponds are the primary wetland ecosystem of the U.S. 

Virgin Islands (Stengel 1998). Virgin Islands National 

Park hosts 34 salt ponds within its boundaries (fig. 15). 

Salt ponds serve many valuable functions. They act as a 

nursery, providing food and shelter for many terrestrial 

and aquatic species. Salt ponds also serve as a sediment 

trap for storm runoff and pollution, thereby reducing the 

amount of siltation and suspended sediments in adjacent 

marine environments. In addition, these vital habitats 

protect the mainland from storm events, acting as a 

barrier against inland erosion (Stengel 1998; Gangemi 

2003).

Salt ponds are created when a bay or inlet is closed off via 

berm formation on an existing obstruction such as a 

coral reef or sandbar. Geologically, ponds form by the 

gradual closing of sheltered bays as fringing reefs grow 

upwards and create rubble berms over which mangroves 

grow (Jarecki 1999; Gangemi 2003). These berms

eventually close the salt pond from the sea (Stengel 

1998), drastically reducing seawater interchange.

Mangroves are necessary for salt pond productivity and 

function. White and black mangroves (Laguncularia 

racemosa and Avicennia germinans) grow in salt ponds

and in the soil and sediment upland from the distinctive 

red mangroves (Rhizophora mangle), which grow in 

saltwater or brackish water in the mudflats near 

shorelines (National Park Service 2009). More than half 
12 NPS Geologic Resources Division

of the mangroves in the U.S. Virgin Islands have been 

destroyed by natural or human causes. Because this 

vegetation type is a vital component of the salt pond 

ecosystem, mangrove species are now protected by the 

Territory of the U.S. Virgin Islands (Gangemi 2003).

Salt ponds host a wide range of physical conditions, 

including major fluctuations in temperature, salinity, 

dissolved oxygen, and turbidity (Gangemi 2003). These 

“extremes” present a challenge for many wetland 

species, but provide a perfect habitat for a variety of fish, 

invertebrate, and bird species. Both terrestrial and 

migratory birds, many threatened or endangered, rely on 

food and protection found within salt ponds (Stengel 

1998). In addition, larval and juvenile species rely on the 

nursery function provided by these ecosystems. 

Mangrove roots provide refuge for a variety of fish and 

invertebrates species, and mangrove leaf litter (organic 

detritus) shelters small invertebrates (Stengel 1998).

The expanding coastal development on St. John has 

increased awareness of the importance of salt ponds. 

Specifically, salt ponds act as an effective sediment trap 

for storm runoff and terrestrial pollution. Sediments and 

pollutants are filtered through a salt pond prior to 

deposition in adjacent marine environments. This 

decreases siltation and suspended sediments in adjacent 

marine habitats, including coral reefs and sea grass beds. 

The decrease in sediments in the marine environment 

can improve water quality (Stengel 1998).

Salt ponds also protect inland environments from 

storms. They serve as a buffer that effectively lessens 

storm erosion and reduces habitat loss in adjacent areas. 

In addition, salt ponds cushion wave action and provide 

a catchment basin for rising tides, thereby acting as a 

flood control agent (Stengel 1998).

Seismic Activity

The Caribbean is a seismically active region (fig. 2). As 

mentioned in the “Geologic Setting,” Virgin Islands 

National Park is situated on the tectonically active 

Caribbean plate, which is moving eastward at about 2 cm 

(0.8 in) per year with respect to both the North American 

and South American plates (fig. 3). The Caribbean plate 

is bounded on the north by a left-lateral, strike-slip fault. 

The southern margin of the plate is marked by a rightlateral, strike-slip fault. The eastern boundary of the 

Caribbean plate is a west-dipping subduction zone, 

down which Atlantic oceanic crust is descending and in 

turn fueling the volcanoes (island arc) of the Lesser 

Antilles. Volcanic activity occurs as far north as the 

island of Saba (Rankin 2002). 

The Virgin Islands are situated between the Greater 

Antilles and the Lesser Antilles. This location (i.e., the 

northeastern corner of the Caribbean plate) is an 

important tectonic position in the Caribbean region. It 

marks a transition from transform (strike-slip) plate 

motion, which is indicative of the Greater Antilles, to the 

convergent (subduction) plate motion represented by the 

volcanic arc of the Lesser Antilles.

Periodic seismic activity, including earthquakes, 

submarine landslides, submarine volcanic eruptions, 

subaerial pyroclastic flows, and tsunamis are common 

throughout the region. Two features are of interest for 

Virgin Island National Park: the Puerto Rico Trench and 

the Anegada Trough. The Puerto Rico Trench, located 

on the boundary between the Caribbean and North 

American plates, is an active fault zone. The trench is a 

depression in the ocean floor that reaches depths of 

9,219 m (30,249 ft), making it the deepest known part of 

the Atlantic Ocean (Miller et al. 1999). The Anegada 

Trough is situated on the Caribbean plate and separates 

St. Croix from the other Virgin Islands. The trough poses 

a significant threat of tsunami (Office of Disaster 

Preparedness 1997). Currently, a U.S. Geological Survey 

(USGS) seismic station in Puerto Rico monitors 

earthquake activity in the U.S. Virgin Islands (U.S. 

Geological Survey 2010).

Paleontological Resources

Paleontological resources (fossils) require science-based 

resource management as directed by the 2009 

Paleontological Resources Preservation Act (Public Law 

111-11). The National Park Service is currently 

developing regulations associated with the Act (J. 

Brunner, Geologic Resources Division, personal 

communication, May 2010). Santucci et al. (2009) suggest 

strategies for monitoring in situ paleontological 

resources.

The NPS conducted a paleontological inventory from 

literature of known and potential fossil occurrences in 

Virgin Islands National Park (Toscano et al. 2010). 

Paleontological resources are not common with the park. 

Nevertheless microfossils called radiolarians were 

discovered in chert of the Cretaceous-aged Water Island 

Formation (Rankin 2002). Limestone clasts in the 

Louisenhoj Formation occasionally preserve fossil 

fragments (Rankin 2002). Holocene (younger than 

11,700 years) coral reef deposits also contain fossil 

fragments. Modern fossil-forming ecosystems exist 

within the park, including nearshore marine mangrove 

areas, shallow seagrass beds, and coral reefs (Toscano et 

al. 2010). 
VIIS Geologic Resources Inventory Report 13

Figure 7. Cobbles and beachrock. The shoreline of Saltpond Bay displays dark-colored cobbles and lighter-colored beachrock. The beachrock 

formed when calcium carbonate precipitated from seawater, causing sand grains to cement together into a calcareous sandstone crust. 

Photograph by K. N. Hall.

Figure 8. Cobblestone beach. Different lithologies create the variety of color of beach sediments at Saltpond Bay along Ram Head Trail. The 

darker cobbles are pieces of basalt of the Water Island Formation derived from the breakup of adjacent ledges and then rounded by wave 

action. The white cobbles are pieces of modern coral, also rounded by wave action. Photograph by K. N. Hall.
14 NPS Geologic Resources Division

Figure 9. Rocky shoreline. Steep rocky slopes (e.g., Ram Head Point) characterize the topography at Virgin Islands National Park. Photograph 

by K. N. Hall.

Figure 10. Elkhorn coral. Most reefs in the Caribbean are “fringing reefs” that grow close to the shore or in small patches. Coral species at 

Virgin Islands National Park include elkhorn (Acropora palmata) and staghorn (Acropora cervicornis). National Park Service photograph 

courtesy Rafe Boulon (Virgin Islands National Park).
VIIS Geologic Resources Inventory Report 15

Figure 11. Columnar jointing. On Leduck Island, exposures of light-colored granitic rock (called trondhjemite) display columnar jointing. This 

feature is commonly exhibited within the Careen Hill Intrusive Suite. The eastern shoreline of St. John is visible in the background. 

Photograph by K. N. Hall.

Figure 12. White Cliffs. Hydrothermal alteration has changed the mineralogy of the Water Island Formation exposed on the east side of Reef 

Bay, St. John. National Park Service photograph by Carolyn Stengel.
16 NPS Geologic Resources Division

Figure 13. Pillow basalt. Water Island Formation, Harbor Point in Coral Bay. A) View looking east. Pillows are as large as a meter across. Pillow 

asymmetry indicates that layers are right side up. B) View looking north shows that pillows in (A) are cross sections of tubes elongated down

dip. Hammer is 28.5 cm (11 in) long. U.S. Geological Survey photographs, figure 4 in Rankin (2002).

Figure 14. Metamorphosed and interlayered sandstone and shale. The adjacent Narrows pluton provided the heat source that 

metamorphosed the Mandal Member of the Tutu Formation at Mary Point. Metamorphism also caused the growth of abundant garnet, 

biotite, and tremolite. Tectonic forces have tilted the rocks, resulting in vertical bedding. Photograph by K. N. Hall.
VIIS Geologic Resources Inventory Report 17

Figure 15. Salt ponds—a primary wetland type at Virgin Islands National Park—serve many ecosystem functions, providing food and shelter 

for both terrestrial and aquatic species. This salt pond is located near Newfound Bay. National Park Service photography courtesy Rafe 

Boulon (Virgin Islands National Park).
18 NPS Geologic Resources Division

Figure 16. Geologic timescale. Included are major life-history and tectonic events occurring on the North American continent. Red lines 

indicate major boundaries between eras. Isotopic ages shown are in Ma. Compass directions in parentheses indicate the regional location of 

individual geologic events. Adapted from the U.S. Geological Survey (http://pubs.usgs.gov/fs/2007/3015/) with additional information from 

the International Commission on Stratigraphy (http://www.stratigraphy.org/view.php?id=25).
VIIS Geologic Resources Inventory Report 19

Map Unit Properties

This section identifies characteristics of map units that appear on the Geologic Resources 

Inventory digital geologic map of Virgin Islands National Park. The accompanying table

is highly generalized and is provided for background purposes only. Ground-disturbing 

activities should not be permitted or denied on the basis of information in this table. 

Geologic maps facilitate an understanding of Earth, its 

processes, and the geologic history responsible for its 

formation. Hence, the geologic map for Virgin Islands 

National Park provided information for the “Geologic 

Issues,” “Geologic Features and Processes,” and 

“Geologic History” sections of this report. Geologic 

maps are two-dimensional representations of complex 

three-dimensional relationships; their color coding 

illustrates the distribution of rocks and unconsolidated 

deposits. Bold lines that cross or separate the color 

patterns mark structures such as faults and folds. Point 

symbols indicate features such as dipping strata, sample 

localities, mines, wells, and cave openings. 

Incorporation of geologic data into a Geographic 

Information System (GIS) increases the usefulness of 

geologic maps by revealing the spatial relationships 

among geologic features, other natural resources, and 

anthropogenic features. Geologic maps are indicators of 

water resources because they show which rock units are 

potential aquifers and are useful for finding seeps and 

springs. Geologic maps are not soil maps, and do not 

show soil types, but they do show parent material—a key 

factor in soil formation. Furthermore, resource managers 

have used geologic maps to make connections between 

geology and biology; for instance, geologic maps have 

served as tools for locating sensitive, threatened, and 

endangered plant species, which may prefer a particular 

rock unit. 

Although geologic maps do not show where earthquakes 

will occur, the presence of a fault indicates past 

movement and possible future seismic activity. Similarly, 

map units show areas that have been susceptible to 

hazards such as landslides, rockfalls, and volcanic 

eruptions. Geologic maps do not show archaeological or 

cultural resources, but past peoples may have inhabited 

or been influenced by depicted geomorphic features. For 

example, alluvial terraces may have been preferred use 

areas and formerly inhabited alcoves may occur at the 

contact between two rock units.

The geologic units listed in the following table 

correspond to the accompanying digital geologic data. 

Map units are listed in the table from youngest to oldest. 

Please refer to the geologic timescale (fig. 16) for the age 

associated with each time period. The table highlights 

characteristics of map units such as: susceptibility to 

erosion and hazards; the occurrence of paleontological 

resources (fossils), cultural resources, mineral resources, 

and caves or karst; and suitability as habitat or for 

recreational use. Some information on the table is 

conjectural and meant to serve as suggestions for further 

investigation.

The GRI digital geologic maps reproduce essential 

elements of the source maps including the unit 

descriptions, legend, map notes, graphics, and report. 

The following reference is the source for the GRI digital 

geologic data for Virgin Islands National Park: 

Rankin, D. W. 2002. Geology of St. John, U.S. Virgin 

Islands. Scale 1:24,000. Professional Paper 1631. U.S. 

Geological Survey, Reston, Virginia, USA.

The GRI team implements a geology-GIS data model 

that standardizes map deliverables. This data model 

dictates GIS data structure including data layer 

architecture, feature attribution, and data relationships 

within ESRI ArcGIS software, increasing the overall 

utility of the data. GRI digital geologic map products 

include data in ESRI shapefile and coverage GIS formats, 

Federal Geographic Data Committee (FGDC)-compliant 

metadata, a Windows help file that contains all of the 

ancillary map information and graphics, and an ESRI 

ArcMap map document file that easily displays the map 

with appropriate symbology. GRI digital geologic data 

are included on the attached CD and are available 

through the NPS Data Store at 

http://science.nature.nps.gov/nrdata/. 

VIIS Geologic Resources Inventory Report 21

Map Unit Properties Table: Virgin Islands National Park

Gray-shaded units are not mapped within Virgin Islands National Park.

Age Map Unit

(Symbol) Features and Description Mineral Occurrence Paleontological and Cultural Resources Resistance to Erosion

QUATERNARY

Surficial 

deposits

(Qs)

Alluvium, swamp deposits, beach deposits, beachrock, and artificial fill None documented

Archaeological 

artifacts including 

Taino, Dutch, and 

African-slave 

cultural resources

Low—Coastal erosion will 

likely continue to damage 

anthropogenic structures 

and cultural artifacts located 

on various beaches

TERTIARY (PALEOGENE AND NEOGENE)

Red Hook 

Tonalite 

Porphyry

(Tr)

Dikes and small hypabyssal intrusions of porphyritic tonalite with as much as 45% phenocrysts; characterized by quartz phenocrysts 1 cm (0.4 in) or 

larger; named for prominent dikes at Red Hook (Eastern St. Thomas quadrangle) where dikes are intruded along brittle faults

Quartz, biotite, hornblende, 

apatite, plagioclase, and vermiculite None documented High

Explosion 

breccias

(Te)

Mafic dike with 60% or more xenoliths; occurs only on east side of Dittlif Point where it spans about 20 m (66 ft) across an outcrop of Water Island 

Formation; cuts diabase dike that is interpreted to be unit Td but could be unit Kcm (gabbro) of Careen Hill Intrusive Suite;

15 to 20 cm (6 to 8 in) thick

Xenoliths include keratophyre, 

greenstone, gabbro, and tonalite None documented High

Hornblende 

lamprophyre 

(Tl)

Dark, magnetite-bearing, aphanitic dikes with prominent hornblende phenocrysts; most Tl dikes are younger than dikes of unit Td, but some Td 

mafic dikes cut Tl

Hornblende, clinopyroxene, and 

plagioclase None documented High

Biotitehornblende 

tonalite

(Tt)

Biotite-hornblende tonalite and minor gabbro, diorite, granite, and pegmatite; produces contact-metamorphic aureole as wide as 2 km (1.2 mi)

Quartz, plagioclase, biotite, 

chlorite, hornblende, orthoclase, 

zircon, clinopyroxene, apatite, 

pyrite, magnetite, diopside, sphene, 

allanite, and calcite

None documented High

Diabase, 

gabbro, and 

diorite

(Td)

Nearly vertical dikes; chilled margins typical, columnar jointing not typical; dikes intrude all stratified units except surficial deposits and are intruded 

by tonalite (Tt); likely includes dikes of more than one age; some may be intrusive equivalents of extrusive rocks in enclosing or overlying stratified 

units, while others may be part of tonalite (Tt) intrusive cycle; a very few cut hornblende lamprophyre (Tl); most interpreted to be part of early 

Tertiary pre-tonalite (Tt) magmatic cycle (Donnelly et al. 1990)

Plagioclase, clinopyroxene, 

hornblende, magnetite, pyrite, 

quartz, amphibole, chlorite, and 

epidote

None documented High

CRETACEOUS

Tutu Formation

(Ktm, Ktmc, 

Ktml, Ktp, Ktpl)

Volcanic wacke, shale, sandstone, conglomerate, calcareous siltstone, limestone, marble, and rare basalt and andesite or their metamorphosed 

equivalents; all rocks are within contact aureole of tonalite (Tt); graded beds, slump folds, and disrupted slabs of metasandstone and metasiltstone in 

metaconglomerate indicate deposition by turbidity currents on an unstable slope, perhaps a trench wall; basal contact not exposed, but it is in 

apparent conformity with underlying Outer Brass Limestone (Ko)

Includes Mandal Member (Ktm) with Congo Cay Limestone Lens (Ktmc) and marble, calc-silicate rock, and marble conglomerate (Ktml); as well as

Picara Member (Ktp) with marble conglomerate and calc-silicate-rich beds north of Maho Point (Ktpl); overall the Mandal Member is finer grained 

than the Picara Member

Calc-silicate rocks contain 

combinations of calcite, quartz, 

plagioclase, tremolite, diopside, 

phlogopite, garnet, epidote, 

wollastonite, sphene, pyrite, and 

other sulfides

None documented Moderate to high

Outer Brass 

Limestone

(Ko)

Thin-bedded (3-m [10-ft]) calc-silicate rock, with beds of white to blue-gray calcite marble (sulfurous odor when broken), and metamorphosed, 

matrix-supported cobble conglomerate with andesite clasts in carbonate matrix; total thickness about 100 m (330 ft)

Calcite, plagioclase, epidote, brown 

isotropic garnet, diopside, 

vesuvianite, and wollastonite

Possible Taino 

quarry source

Moderate to high

Louisenhoj 

Formation

(Kl)

Strongly cemented volcanic conglomerate, breccia, volcanic wacke, and shale in graded beds as thick as 6 m (20 ft); rare chert and limestone; minor 

pillow basalt and possible aa lava; basalt and andesite—both as the dominant clasts in the strata and as extrusive rocks—are characterized by about 

20% prominent phenocrysts of stubby plagioclase and clinopyroxene; differences in clast populations suggest local sources; from central St. John to 

the north and east, most rocks are foliated; at least 1.5 km (0.9 mi) thick on west coast of St. John, and may be as thin as 0.5 km (0.3 mi) at Leinster Bay; 

overlies the Water Island Formation with apparent conformity

Includes porphyritic, locally vesicular andesite lava (Kla) and porphyritic, locally amygdaloidal basalt and pillow basalt (Klb)

Clinopyroxene and plagioclase; 

biotite, pale amphibole and epidote 

may appear in andesite; epidote, 

hornblende and biotite may appear 

in basalt

Limestone clasts, 

some fossiliferous, 

on Rata and 

Ramgoat Cays

Moderate to high
VIIS Geologic Resources Inventory Report 22

Age Map Unit

(Symbol) Features and Description Mineral Occurrence Paleontological and Cultural Resources Resistance to Erosion

CRETACEOUS

Lameshur 

VolcanicIntrusive 

Complex

(Klm)

Dominantly keratophyre and volcaniclastic rock derived from it; also includes basalt and basaltic andesite, trondhjemite, gabbro, and chert. 

Keratophyre occurs as lava flows, breccia, layered tuff, dikes, and small hypabyssal intrusive rock; several varieties of keratophyre are distinguished by 

the size and type of phenocrysts. Mafic rocks occur as pillow lava, pillow breccia, dikes, and rare small plutons. Local hydrothermal alteration may 

include boxwork texture and gossan. Named for Lameshur on the southern coast of St. John.

Quartz and plagioclase None documented Low to high

Lameshur Volcanic-Intrusive Complex

Careen 

Hill 

Intrusive 

Suite

(Kct, Kcc, 

Kcp, Kca, 

Kcf, Kcm, 

Kcsd)

Trondhjemite, keratophyre (intrusive equivalents of all keratophyre units of the Water Island Formation), and gabbro; distinct columnar jointing 

present on Leduck Island and in many dikes and sills; no sequence of intrusion recognized. Named from Careen Hill in Charlotte Amalie.

Includes trondhjemite (Kct), coarsely porphyritic keratophyre (Kcc), porphyritic keratophyre (Kcp), phenocryst-poor keratophyre (Kca), plagioclasephyric keratophyre (Kcf), gabbro (Kcm), and sheeted dike complex (Kcsd). Trondhjemite and keratophyre form sharp hills on the south coast of St. 

John.

None documented None documented Low to high

Water 

Island 

Formation

(Kwp, 

Kwa, Kwf, 

Kws, 

Kww, 

Kwr)

Dominantly extrusive keratophyres and volcaniclastics rocks derived from it; about 20% basaltic lava (mostly pillowed), breccia, and hyaloclastite; 

minor radiolarian chert; no through-going stratigraphic order recognized; extrusive equivalent of Careen Hill Intrusive Suite; ash-flow tuffs notably 

sparse; groundmass of keratophyre commonly spherulitic; excellent exposures of pillow breccias and hyaloclastites are found west of Ram Head Trail, 

on Harbor Point, and on the peninsulas of Turner and Dittlif points; base of the Water Island Formation not exposed but it was likely deposited on 

oceanic plateau crust

Includes porphyritic keratophyre (Kwp) (superbly exposed in a series of cascades along Battery Gut), phenocryst-poor keratophyre (Kwa) (dominant 

unit of the Water Island Formation on St. John and well exposed along Fish Gut Bay), plagioclase-phyric keratophyre (Kwf), basalt and basaltic 

andesite (Kws), volcanic wacke and bedded tuff (Kww), and radiolarian chert (Kwr)

None documented

Radiolaria within 

bedded chert at 

Kiddel Point and 

Saltpond Bay

Moderate to high
VIIS Geologic Resources Inventory Report 23

Geologic History

This section describes the rocks and unconsolidated deposits that appear on the digital 

geologic map of Virgin Islands National Park, the environment in which those units were 

deposited, and the timing of geologic events that created the present landscape.

More than 100 million years of geologic history are

exposed on the island of St. John. This history ranges

from Lower Cretaceous submarine volcanic eruptions to 

modern-day surficial deposits that form the island’s 

magnificent beaches.

Most of St. John is composed of volcanic rocks (e.g., 

keratophyres, basalt, and andesite) or sedimentary 

material derived from these rocks (Rankin 2002).

Calcareous rocks and chert are also present in small 

amounts. Stratified rocks, except for recent deposits, are 

Cretaceous age. Dikes, sills, and batholiths of Tertiary 

(now officially called “Neogene;” International 

Commission on Stratigraphy 2009) age have intruded 

these rocks.

Lameshur Volcanic-Intrusive Complex

Excellent exposures of the oldest rocks in Virgin Islands 

National Park occur on southern and southeastern St.

John. Renamed the Lameshur Volcanic-Intrusive 

Complex by Rankin (2002), these rocks are among the 

oldest in the Caribbean and predate the development of 

early island-arc volcanism in the Greater Antilles. 

Geologically, the Virgin Islands constitute the eastern 

extremity of the Greater Antilles and are part of the same 

magmatic arc (Rankin 2002). The complex of rocks is 

estimated to be at least 2 km (1.2 mi) thick (Rankin 2002);

although the base is not visible, it is presumed to be 

underlain by oceanic crust (Donnelly 1989). The 

Lameshur Volcanic-Intrusive Complex includes both the 

Water Island Formation and the Careen Hill Intrusive 

Suite. 

Keratophyres and volcaniclastic rocks account for more 

than 80% of the Water Island Formation, which 

represents quiet eruptions in relatively deep water 

(indicated by the presence of radiolarian chert) in an 

extensional (pulling apart) oceanic environment.

Additionally, the formation contains basaltic lavas, 

breccias, and hyaloclastites. 

The Careen Hill Intrusive Suite is the intrusive equivalent 

of the Water Island Formation; these rocks did not flow 

onto the ocean floor, rather they cooled below the ocean 

floor. This suite is composed mainly of trondhjemites, 

porphyritic keratophyres, and gabbros (Rankin 2002).

Louisehoj Formation

The Late Cretaceous Louisehoj Formation was 

deposited onto the Water Island Formation during 

development of an island arc. Subduction-related 

volcanism in shallow marine waters created more than 

2,100 m (7,000 ft) of greenish-gray or grayish-blue green

andesite ash beds and pyroclastic breccia. Graded 

bedding throughout the formation records submarine 

slides and slumps of volcanic material. The variety of 

clast compositions and sizes, particularly in the 

conglomeratic beds of the formation, suggests that 

numerous volcanic vents were located nearby.

The Louisenhoj Formation dominates the western half of 

St. John, including Cruz Bay, Trunk Bay, and Cinnamon 

Bay. Louisenhoj rock has inherent strength, creating 

difficulties during construction projects. 

Outer Brass Limestone

During a time of volcanic quiescence, the Outer Brass 

Limestone was deposited on top of the Louisenhoj 

Formation in a quiet marine environment. Deposition of 

the limestone likely occurred on moderate slopes at a few 

hundred feet in depth. The Outer Brass Limestone is 

about 100 m (330 ft) thick on St. John and consists of 

thinly interlayered calc-silicate rock, white to blue-gray 

calcite marble, and calcareous-matrix andesite 

conglomerate. Contact metamorphism of the calcareous 

rocks by Neogene plutons produced an interesting 

assemblage of minerals, including tremolite, diopside, 

phlogopite, garnet, epidote, wollastonite, vesuvianite, 

sphene, pyrite, and other sulfides (Rankin 2002). The 

marble beds, which are up to 3 m (10 ft) thick, may be the 

source of Taino trading beads (figs. 17, 18). This unit 

forms a discontinuous belt extending from Maho Bay to 

Brown Bay, with excellent exposures at Annaberg Point

on the north shore of St. John.

Although the Outer Brass Limestone is a thin, minor unit 

on St. John, it is useful for stratigraphically separating the 

conglomeratic Louisenhoj Formation from the lesser 

conglomeratic Tutu Formation (Rankin 2002).

Tutu Formation

After deposition of the Outer Brass Limestone, 

volcanism resumed and the Tutu Formation formed in 

an island-arc setting. Characterized by volcanic wacke, 

shale, conglomerate, calcareous siltstone, limestone, and 

rare basalt and andesite (or their metamorphic 

equivalents), most of the material seems to have been 

deposited by turbidity currents, suggesting deposition on 

an unstable slope such as a trench wall leading into an 

accretionary wedge (Rankin 2002). Volcaniclastic 

fragments within the Tutu Formation are generally sand 

and silt size, suggesting that the volcanic source was 

farther away than the Louisenhoj vents (Rankin 2002).

Additionally, a distinct fining upward implies 

increasingly distant volcanic sources. The extrusive 

igneous rocks of the Tutu Formation are the last 

evidence of volcanism on St. John.
24 NPS Geologic Resources Division

The Tutu Formation is divided into two components: the 

older Picara Member and the overlying, finer grained 

Mandal Member. A thin limestone lens referred to as the 

Congo Cay Limestone Lens is a subcomponent of the 

Mandal Member. The Tutu Formation extends from 

Whistting Cay to Leinster Point.

Dikes, Narrows Pluton, and Virgin Gorda Batholith

The Neogene Period on St. John is marked by intrusive 

activity that included a mafic dike swarm followed by 

plutons of biotite-hornblende tonalite and minor gabbro, 

diorite, granite, and pegmatite. The latter includes the 

Narrows pluton and the Virgin Gorda batholith, which 

produced a contact metamorphosed aureole as wide as 2 

km (1.2 mi). Individual dikes range in thickness from a 

few centimeters to several meters. 

Surficial Deposits

Today, Quaternary alluvium, swamp deposits, beach 

deposits, beachrock, bay mouth bars, playa deposits,

boulder fields, and artificial fill compose the sand 

beaches and low-lying areas of Virgin Islands National 

Park (Rankin 2002).

Figure 17. Taino trading bead. The Taino used marble to create trading beads and jewelry. Beds of marble occur in the Outer Brass Limestone. 

Photograph by K. N. Hall.

Figure 18. Marble. Contact metamorphism transformed beds of the Outer Brass Limestone into marble. This figure shows a marble boulder 

near Annaberg Point. Note the folded beds, which are indicative of contact metamorphism. Photograph by K. N. Hall.
VIIS Geologic Resources Inventory Report 25

Glossary

This glossary contains brief definitions of technical geologic terms used in this report. Not all 

geologic terms used are referenced. For more detailed definitions or to find terms not listed 

here please visit: http://geomaps.wr.usgs.gov/parks/misc/glossarya.html. Definitions are 

based on those in the American Geological Institute Glossary of Geology (fifth edition; 2005).

accretionary prism (or wedge). A wedge-shaped body of 

deformed rock consisting of material scraped off of 

subducting oceanic crust at a subduction zone. 

Accretionary prisms form in the same manner as a pile 

of snow in front of a snowplow. 

allanite. A brownish-black silicate mineral of the epidote 

group. Found in igneous rocks, allanite contains a 

significant amount of rare earth elements.

amphibole. A common group of rock-forming silicate 

minerals. Hornblende is the most abundant type.

andesite. Volcanic rock commonly associated with 

subduction zone volcanoes. Named for the subduction 

zone volcanoes of the Andes Mountains.

apatite. A group of variously colored phosphate

minerals. Tooth enamel and bones contain minerals 

from the apatite group.

ash (volcanic). Fine material ejected from a volcano (also 

see “tuff”).

asthenosphere. Earth’s relatively weak layer or shell 

below the rigid lithosphere.

augite. A dark-green to black pyroxene mineral that 

contains large amounts of aluminum, iron, and 

magnesium. Found in igneous and high-temperature 

metamorphic rocks.

aureole. A zone surrounding an igneous intrusion in 

which the country rock shows the effects of contact 

metamorphism from the high temperature, molten 

material.

basin (sedimentary). Any depression, from continental to 

local scales, into which sediments are deposited.

batholith. A massive, discordant pluton, larger than 100 

km2 (40 mi2

), and often formed from multiple 

intrusions of magma.

beach. A gently sloping shoreline covered with sediment, 

commonly formed by the action of waves and tides.

beachrock. A poorly-cemented to well-cemented 

sedimentary rock formed in the intertidal zone 

consisting of sand and gravel (fragments of rocks, 

marine invertebrate shells, or coral) cemented with 

calcium carbonate.

bed. The smallest sedimentary strata unit, commonly 

ranging in thickness from one centimeter to a meter or 

two and distinguishable from beds above and below.

bedrock. A general term for the rock that underlies soil 

or other unconsolidated, surficial material.

berm. A low, impermanent, nearly horizontal or 

landward-sloping bench, shelf, or ledge on the 

backshore of a beach.

biotite. A widely distributed and important rock-forming 

mineral of the mica group. Forms thin, flat sheets.

boxwork. Usually in caves; a network of resistant 

intersecting fins, usually of calcite, that project 

outward from the intervening, more deeply weathered 

bedrock.

breccia (volcanic). A coarse-grained, generally unsorted 

volcanic rock consisting of partially welded angular 

fragments of ejected material such as tuff or ash.

calcite. A common rock-forming mineral: CaCO3 

(calcium carbonate).

cementation. Chemical precipitation of material into 

pores between grains that bind the grains into rock.

chemical sediment. A sediment precipitated directly from 

solution (also called nonclastic).

chert. A extremely hard sedimentary rock with 

conchoidal (smooth curved surface) fracturing. It

consists chiefly of interlocking crystals of quartz Also 

called “flint.”

clastic. Describes rock or sediment made of fragments of 

pre-existing rocks (clasts).

clay. Can be used to refer to clay minerals or as a 

sedimentary fragment size classification (less than 

1/256 mm [0.00015 in]).

clinopyroxene. A group name for pyroxene minerals 

crystallizing in the monoclinic system. Important rockforming minerals; common in igneous and 

metamorphic rocks.

columnar joints. Parallel, prismatic columns, polygonal in 

cross section, in basaltic flows and sometimes in other 

extrusive and intrusive rocks; they form as a result of 

contraction during cooling.

concordant. Strata with contacts parallel to the 

orientation of adjacent strata.

conglomerate. A coarse-grained, generally unsorted, 

sedimentary rock consisting of cemented, rounded 

clasts larger than 2 mm (0.08 in).

contact metamorphism. Changes in rock as a result of 

contact with an igneous body.

convergent boundary. A plate boundary where two 

tectonic plates are colliding.

country rock. The rock surrounding an igneous intrusion 

or pluton. Also, the rock enclosing or traversed by a 

mineral deposit.

deformation. A general term for the processes of faulting, 

folding, and shearing of rocks as a result of various 

Earth forces such as compression (pushing together) 

and extension (pulling apart).

dike. A narrow igneous intrusion that cuts across 

bedding planes or other geologic structures.

diopside. A mineral of the pyroxene group. Found in 

mafic, ultramafic igneous rocks and some areas of 

contact metamorphism.

diorite. A type of plutonic igneous rock. It is the 

approximate intrusive equivalent of andesite.
26 NPS Geologic Resources Division

discordant. Describes contacts between strata that cut 

across or are set at an angle to the orientation of 

adjacent rocks.

divergent boundary. An active boundary where tectonic 

plates are moving apart (e.g., a spreading ridge or 

continental rift zone).

eolian. Describes materials formed, eroded, or deposited 

by or related to the action of the wind. Also spelled 

“Aeolian.”

epidote. A yellow-green, pistachio-green, or blackishgreen mineral (calcium, aluminum, iron silicate).

Common rock-forming mineral, found in 

metamorphic rocks.

extension. A type of strain resulting from forces “pulling 

apart.” Opposite of compression.

extrusive. Describes igneous material that has erupted 

onto Earth’s surface.

fault. A break in rock along which relative movement has 

occurred between the two sides.

feldspar. A group of abundant (more than 60% of Earth’s 

crust), light-colored to translucent silicate minerals 

found in all types of rocks. Usually white and gray to 

pink. May contain potassium, sodium, calcium, 

barium, rubidium, and strontium along with 

aluminum, silica, and oxygen.

felsic. Describes an igneous rock having abundant lightcolored minerals such as quartz, feldspars, or 

muscovite. Compare to “mafic.”

foliation. A preferred arrangement of crystal planes in 

minerals. In metamorphic rocks, the term commonly 

refers to a parallel orientation of planar minerals such 

as micas.

fracture. Irregular breakage of a mineral; also any break 

in a rock (e.g., crack, joint, or fault).

gabbro. A group of dark-colored, intrusive igneous 

rocks. The intrusive equivalent of basalt. 

garnet. A hard mineral that has a glassy luster, often with 

well defined crystal faces, and a variety of colors, dark 

red being characteristic. Common in metamorphic 

rocks.

geology. The study of Earth including its origin, history, 

physical processes, components, and morphology.

gossan. An iron-bearing weathered product overlying a 

sulfide deposit.

granite. An intrusive igneous (plutonic) rock composed 

primarily of quartz and feldspar. Mica and amphibole 

minerals are also common. Intrusive equivalent of 

rhyolite.

graben. A down-dropped structural block bounded by 

steeply dipping, normal faults (also see “horst”).

greenstone. A general term for any compact dark green 

altered or metamorphosed basic igneous rock owing 

its color to chlorite, actinolite, or epidote minerals.

hornblende. The most common mineral of the 

amphibole group. Hornblende is commonly black and 

occurs in distinct crystals or in columnar, fibrous, or 

granular forms.

horst. Areas of relative “up” between grabens, 

representing the geologic surface left behind as 

grabens drop. The best example is the Basin-andRange province of Nevada. The basins are grabens 

and the ranges are weathered horsts. Grabens become 

a locus for sedimentary deposition (also see “graben”).

hyaloclastite. A deposit formed by the flow or intrusion 

of lava or magma into water, ice, or water-saturated 

sediment, and its consequent shattering into small 

angular fragments.

hypabyssal. An igneous rock formed at a shallow depth. 

igneous. Refers to a rock or mineral that originated from 

molten material; one of the three main classes of 

rocks—igneous, metamorphic, and sedimentary.

intrusion. A body of igneous rock that invades (pushes 

into) older rock. The invading rock may be a plastic 

solid or magma.

island arc. A line or arc of volcanic islands formed over 

and parallel to a subduction zone.

keratophyres. A term applied to salic (silicon or 

aluminum-rich minerals) or hypabyssal rocks.

landslide. Any process or landform resulting from rapid, 

gravity-driven mass movement.

limestone. A sedimentary rock consisting chiefly of 

calcium carbonate, primarily in the form of the mineral 

calcite.

lithology. The physical description or classification of a 

rock or rock unit based on characters such as its color, 

mineral composition, and grain size.

lithosphere. The relatively rigid outmost shell of Earth’s 

structure, 50 to 100 km (31 to 62 mi) thick, that 

encompasses the crust and uppermost mantle.

mafic. Describes dark-colored rock, magma, or minerals 

rich in magnesium and iron. Compare to “felsic.”

magma. Molten rock beneath Earth’s surface capable of 

intrusion and extrusion. 

mantle. The zone of Earth’s interior between the crust 

and core.

member. A lithostratigraphic unit with definable 

contacts; a member subdivides a formation.

meta–. A prefix used with the name of a sedimentary or 

igneous rock, indicating that the rock has been 

metamorphosed.

metamorphic. Describes the process of metamorphism 

or its results. One of the three main classes of rocks—

igneous, metamorphic, and sedimentary.

metamorphism. Literally, a change in form. 

Metamorphism occurs in rocks through mineral 

alteration, formation, and/or recrystallization from 

increased heat and/or pressure.

mica. A prominent rock-forming mineral of igneous and 

metamorphic rocks. It has perfect basal cleavage 

meaning that it forms flat sheets.

microplate. A small lithospheric plate.

mineral. A naturally occurring, inorganic crystalline solid 

with a definite chemical composition or compositional 

range.

monoclinic. One of the six crystal systems for classifying 

minerals.

mud flat. A relatively level area of fine silt along a shore, 

alternately covered and uncovered by the tide or 

covered by shallow water.

oceanic crust. Earth’s crust formed at spreading ridges 

that underlies the ocean basins. Oceanic crust is 6 to 7 

km (3 to 4 miles) thick and generally of basaltic 

composition.

parent rock. Rock from which soil, sediments, or other 

rocks are derived.
VIIS Geologic Resources Inventory Report 27

pebble. Generally, small rounded rock particles from 4 to 

64 mm (0.16 to 2.52 in) in diameter.

pegmatite. An exceptionally coarse-grained intrusive 

igneous rock, with interlocking crystals, usually found 

in irregular dikes, lenses, and veins, especially at the 

margins of batholiths.

phenocryst. A coarse (large) crystal in a porphyritic

igneous rock.

phlogopite. A magnesium-rich mineral of the mica 

group.

plastic. Capable of being deformed permanently without 

rupture.

plateau. A broad, flat-topped topographic high 

(terrestrial or marine) of great extent and elevation 

above the surrounding plains, canyons, or valleys.

plagioclase. A group of feldspars and common rockforming mineral.

playa (coastal). A small generally sandy land area at the 

mouth of a stream or along the shore of a bay.

plume. A persistent, pipe-like body of hot material 

moving upward from Earth’s mantle into the crust.

pluton (plutonic). A body of intrusive igneous rock that 

crystallized at some depth beneath Earth’s surface.

porphyry. An igneous rock consisting of abundant coarse 

crystals in a fine-grained matrix.

pyrite. A common, pale-bronze or brass-yellow, cubic 

mineral.

radiolarian. Occurring from the Cambrian Period to the 

present, radiolarians are zooplankton that occurs 

throughout the ocean; their skeletal remains (often 

siliceous) cover large portion of the ocean bottom.

radiolarian chert. A well-bedded, microcrystalline rock 

composed primarily of Radiolaria with well-developed 

siliceous cement or groundmass.

sand. A clastic particle smaller than a granule and larger 

than a silt grain, having a diameter in the range of 1/16 

mm (0.0025 in) to 2 mm (0.08 in).

sandstone. Clastic sedimentary rock of predominantly 

sand-sized grains.

sediment. An eroded and deposited, unconsolidated 

accumulation of rock and mineral fragments.

sedimentary rock. A consolidated and lithified rock 

consisting of clastic and/or chemical sediment(s). One 

of the three main classes of rocks—igneous, 

metamorphic, and sedimentary.

shale. A clastic sedimentary rock made of clay-sized 

particles that exhibit parallel splitting properties.

silicate. A compound whose crystal structure contains 

the SiO4 tetrahedra.

sill. An igneous intrusion that is of the same orientation 

as the surrounding rock.

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay (1/256 to 

1/16 mm [0.00015 to 0.002 in]).

siltstone. A variably lithified sedimentary rock composed 

of silt-sized grains.

skarn. Calcium-bearing silicates derived from nearly pure 

limestone and dolomite with the introduction of large 

amounts of silica, aluminum, iron, and magnesium.

slope. The inclined surface of any geomorphic feature or 

measurement thereof. Synonymous with “gradient.”

slump. A generally large, coherent mass movement with a 

concave-up failure surface and subsequent backward 

rotation relative to the slope.

spherulitic. Volcanic igneous texture dominated by 

spherical bodies of radiating mineral fibers.

strata. Tabular or sheetlike masses or distinct layers of 

rock.

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. 

Said to be “sinistral” (left-lateral) if relative motion of 

the block opposite the observer appears to be to the 

left. “Dextral” (right-lateral) describes relative motion 

to the right.

subduction zone. A convergent plate boundary where 

oceanic lithosphere descends beneath a continental or 

oceanic plate and is carried down into the mantle.

sulfide. A mineral compound characterized by the 

linkage of sulfur with a metal or semimetal such a 

galena or pyrite.

tectonic. Relating 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.

tonalite. A type of plutonic (intrusive) rock.

topography. The general morphology of Earth’s surface, 

including relief and locations of natural and 

anthropogenic features.

transform boundary. A type of plate boundary at which

lithosphere is neither created or destroyed, and plates 

slide past each other on a strike-slip fault.

tremolite. A white to dark-gray monoclinic mineral of 

the amphibole group.

triclinic. One of the six crystal systems for classifying 

minerals.

tuff. Generally fine-grained, igneous rock formed of 

consolidated volcanic ash.

turbidite. A sediment or rock deposited from a turbidity 

current.

turbidity current. A density current in water, air, or other 

fluid, caused by different amounts of matter in 

suspension; specifically a bottom-flowing current 

laden with sediment, moving swiftly under the 

influence of gravity down a subaqueous slope and 

spreading horizontally on the floor of a body of water.

vent. An opening at Earth’s surface where volcanic 

materials emerge.

vermiculite. A group of mica-rich clay minerals related to 

chlorite and montmorillonite.

vesuvianite. A dense, brittle mineral, usually brown, 

yellow, or green, commonly found in contactmetamorphosed limestone.

wackestone. A “dirty” sandstone that consist of a 

mixture of poorly sorted mineral and rock fragments 

in an abundant matrix of clay and fine silt.

wollastonite. A mineral (CaSiO3) found in contactmetamorphism limestone; it may be white, gray, 

brown, red, or yellow.

xenolith. A rock particle, formed elsewhere, entrained in 

magma as an inclusion.
28 NPS Geologic Resources Division

Literature Cited

This section lists references cited in this report. A more complete geologic bibliography is

available from the NPS Geologic Resources Division.

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Lakewood, Colorado, USA. 

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Donnelly, T. W. 1989. Geologic history of the Caribbean 

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An Overview. Geological Society of America, Boulder, 

Colorado, USA.

Donnelly, T. W., D. Beets, M. J. Carr, T. Jackson, G.

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G. Wadge, and D. Westercamp. 1990. History and 

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of North America: The Caribbean Region, volume H. 

Geological Society of America, Boulder, Colorado, 

USA.

Gangemi, A. 2003. Ecological assessment of salt ponds on 

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Institute of Technology, Cambridge, Massachusetts, 

USA. 

Gladfelter, W. B., E. H. Gladfelter, R. K. Monahan, J. C. 

Ogden, and R. F. Dill. 1977. Environmental studies of 

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U.S.V.I. Fairleigh Dickinson University, West Indies 

Laboratory, St. Croix, U.S. Virgin Islands.

Hall, K. N. 2005. Buck Island Reef National Monument: 

Geologic resource management issues, scoping 

summary. Geologic Resource Evaluation. National 

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Colorado, USA. http://www.nature.nps.gov/

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March 5, 2010).

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Symposium. University of the Virgin Islands, Eastern 

Caribbean Center, St. Thomas, U.S. Virgin Islands. 

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2009. Global climate change impacts in the United 

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July 15, 2010).

Kellogg, C. A., and D. W. Griffin. 2003. African dust 

carries microbes across the ocean: Are they affecting 

human and ecosystem health? Open-File Report 03-

028. U.S. Geological Survey, Reston, Virginia, USA. 

http://coastal.er.usgs.gov/african_dust/ofr-2003-

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national parks, monuments, and seashores. W. W. 

Norton & Company, Inc., New York, New York, USA.

Loomis, C. 2006. GIS in the Virgin Islands National Park 

and the Coral Reef National Monument. Presentation 

at ESRI Federal User Conference, January 31–

February 2, 2006, Washington, D.C., USA. 

Lundgren, I. 2008. The decline of elkhorn coral at Buck 

Island Reef National Monument: Protecting the first 

threatened coral species. Park Science 25(1):36-41.

Mainella, F. P. 2002. Statement of Fran P. Mainella, 

Director, National Park Service, Department of the 

Interior, before the Subcommittee on National Parks, 

Recreation and Public Lands, House Committee on 

Resources concerning the Virgin Islands National Park 

and the Virgin Islands Coral Reef National 

Monument, July 20, 2002.

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Watterson, and Z. –C. Zhao. 2007. Global Climate 

Projections. in Solomon, S., D. Qin, M. Manning, Z. 

Chen, M. Marquis, K. B. Averyt, M. Tignor, and H. L. 
VIIS Geologic Resources Inventory Report 29

Miller, editors. Climate Change 2007: The Physical 

Science Basis. Contribution of Working Group I to the 

Fourth Assessment Report of the Intergovernmental 

Panel on Climate Change. Cambridge University Press, 

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and P. G. Olcott. 1999. Ground water atlas of the 

United States: Segment 13—Alaska, Hawaii, Puerto 

Rico, and the U.S. Virgin Islands. HA 730-N. U.S. 

Geological Survey, Reston, Virginia, USA. 

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Park: Mangroves. http://www.nps.gov/viis/

naturescience/mangroves.htm (accessed February 17, 

2010).

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Park: People. 

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(accessed February 12, 2010).

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Park: Nonnative Species. 

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es.htm (accessed July 12, 2010).

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National Park recreational visitors. National Park 

Service, Public Use Statistics Office, Denver, Colorado, 

USA. http://www.nature.nps.gov/stats/ (accessed July 

15, 2010).

Nelson, K., and R. Beavers. 2002. Coastal geology 

mapping protocols for the Atlantic and Gulf Shore 

national park units. TIC #D-2269. National Park 

Service, Lakewood, Colorado, USA.

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for the island of Anegada. The British Virgin Islands 

Hazard and Risk Assessment Project. Department of 

Disaster Management, Tortola, British Virgin Islands. 

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%20Evacuation%20Plan%20(2).pdf (accessed March 

11, 2010).

Pendleton, E. A., E. R. Thieler, and S. J. Williams. 2004.

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National Park to sea-level rise. Open-File Report 2004-

1398. U.S. Geological Survey, Reston, Virginia, USA.

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11, 2010).

Pindell, J. L., and S. F. Barrett. 1990. Geological evolution 

of the Caribbean region: A plate tectonics perspective. 

Pages 405–432 in G. Dengo and J. E. Case, editors. The 

Geology of North America: The Caribbean Region,

volume H. Geological Society of America, Boulder, 

Colorado, USA.

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Islands. Scale 1:24,000. Professional Paper 1631. U.S. 

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Virgin Islands. Final report. Wetlands Protection C-21. 

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and Wildlife, Department of Planning and Natural 

Resources, Washington, D.C., USA.

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2010. Paleontological resource inventory and 

monitoring—South Florida / Caribbean Network. 

Natural Resource Technical Report 

NPS/NRPC/NRTR—2010/335. National Park Service, 

Fort Collins, Colorado, USA.

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W. Jaap, K. Banks, J. Delaney, B. D. Keller, R. Speiler, 

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N. Vander Velde. 2002. The state of coral reef 

ecosystems of the United States and Pacific Freely 

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Centers for Coastal Ocean Science, Silver Spring, 

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coralreef/coral2008/welcome.html (accessed February 

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Organization (UNESCO). 2000. The MAB Program, 

biosphere reserve information, United States of 

America, Virgin Islands. http://www.unesco.org/

mabdb/br/brdir/directory/biores.asp?code=USA+25&

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Central America. http://earthquake.usgs.gov/regional/

world/seismicity/m_america.php (accessed February 

12, 2010).

U.S. Geological Survey. 2010. Earthquake Hazards 

Program: Caribbean earthquake information. National 

Earthquake Information Center, Golden, Colorado, 

USA. 

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php?regionID=27 (accessed June 10, 2010).
30 NPS Geologic Resources Division

Wieczorek, G. F. and J. B. Snyder. 2009. Monitoring 

slope movements. Pages 245–271 in Young, R. and L. 

Norby, editors. Geological Monitoring. Geological 

Society of America, Boulder, Colorado, USA.

Zanhniser, E. 1999. U.S. Virgin Islands: A guide to 

national parklands in the United States Virgin Islands, 

United States. National Park Handbook Series 157. 

National Park Service, Division of Publications, 

Washington, D.C., USA.

Zengerle, P. 2007. Subtropical storm Olga forms in 

Caribbean. Reuters. 

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(accessed April 9, 2010).

Zitello, A. G., L. J. Bauer, T. A. Battista, P. W. Mueller, M. 

S. Kendall, and M. E. Monaco. 2009. Shallow-water 

benthic habitats of St. John, U.S. Virgin Islands. 

Technical Memorandum NOS NCCOS 96. National 

Oceanic and Atmospheric Administration, Silver 

Spring, Maryland, USA. 

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c_usvi.html (accessed April 19, 2010).
VIIS Geologic Resources Inventory Report 31

Additional References

This section lists additional references, resources, and Web sites that may be of use to 

resource managers.

Climate Change Information

Global change impacts in the United States (report): 

http://www.globalchange.gov/publications/reports/sci

entific-assessments/us-impacts

NPS Climate Change Response Program:

http://www.nature.nps.gov/climatechange/index.cfm

Geology of National Park Service Areas

National Park Service Geologic Resources Division 

(Lakewood, Colorado). http://nature.nps.gov/geology/

NPS Geologic Resources Inventory. 

http://www.nature.nps.gov/geology/inventory/gre_pu

blications.cfm

U.S. Geological Survey Geology of National Parks 

(includes 3D photographs). 

http://3dparks.wr.usgs.gov/

Harris, A. G., E. Tuttle, and S. D. Tuttle. 2003. Geology of 

National Parks. Sixth Edition. Kendall/Hunt 

Publishing Co., Dubuque, Iowa, USA.

Kiver, E. P. and D. V. Harris. 1999. Geology of U.S. 

parklands. John Wiley and Sons, Inc., New York, New 

York, USA.

Lillie, R. J. 2005. Parks and Plates: The geology of our 

national parks, monuments, and seashores. W.W. 

Norton and Co., New York, New York, USA.

[Geared for interpreters].

NPS Geoscientist-in-the-parks (GIP) internship and 

guest scientist program. 

http://www.nature.nps.gov/geology/gip/index.cfm

Resource Management/Legislation Documents

NPS 2006 Management Policies (Chapter 4; Natural 

Resource Management): 

http://www.nps.gov/policy/mp/policies.html#_Toc157

232681

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

R. Young and L. Norby, editors. Geological 

Monitoring. Geological Society of America, Boulder, 

Colorado.

[Web site under development]. Contact the Geologic 

Resources Division to obtain a copy.

NPS Technical Information Center (Denver, repository 

for technical (TIC) documents): http://etic.nps.gov/

Geological Survey Web Sites

Oregon Department of Geology and Mineral Industries 

(DOGAMI): 

http://www.oregongeology.org/sub/default.htm

U.S. Geological Survey: http://www.usgs.gov/

Geological Society of America: 

http://www.geosociety.org/

American Geological Institute: http://www.agiweb.org/

Association of American State Geologists: 

http://www.stategeologists.org/

Other Geology/Resource Management Tools

Bates, R. L. and J. A. Jackson, editors. American 

Geological Institute dictionary of geological terms (3rd 

Edition). Bantam Doubleday Dell Publishing Group, 

New York.

U.S. Geological Survey National Geologic Map Database 

(NGMDB): http://ngmdb.usgs.gov/

U.S. Geological Survey Geologic Names Lexicon 

(GEOLEX; geologic unit nomenclature and summary): 

http://ngmdb.usgs.gov/Geolex/geolex_home.html

U.S. Geological Survey Geographic Names Information 

System (GNIS; search for place names and geographic 

features, and plot them on topographic maps or aerial 

photos): http://gnis.usgs.gov/

U.S. Geological Survey GeoPDFs (download searchable 

PDFs of any topographic map in the United States): 

http://store.usgs.gov (click on “Map Locator”).

U.S. Geological Survey Publications Warehouse (many 

USGS publications are available online): 

http://pubs.usgs.gov

U.S. Geological Survey, description of physiographic 

provinces: http://tapestry.usgs.gov/Default.html
32 NPS Geologic Resources Division

Appendix A: Overview of Digital Geologic Data

The following page is an overview of the digital geologic data for Virgin Islands National 

Park. For a poster-size PDF of this overview and complete digital data, please see the

included CD or visit the Geologic Resources Inventory publications web site: 

http://www.nature.nps.gov/geology/inventory/gre_publications.cfm.

VIIS Geologic Resources Inventory Report 35

Appendix B: Scoping Meeting Participants

The following is a list of participants from the GRI scoping session for Virgin Islands 

National Park, held on April 7–9, 2004. The contact information and email addresses in 

this appendix may be outdated; please contact the Geologic Resources Division for 

current information. The scoping meeting summary was used as the foundation for this 

GRI report. The original scoping summary document is available on the GRI web site: 

http://www.nature.nps.gov/geology/inventory/gre_publications.cfm.

Name Affiliation Position Phone Email

Rebecca Beavers NPS, Geologic Resources 

Division

Coastal Geologist 303-987-6945 Rebecca_Beavers@nps.gov

Rafe Boulon NPS, Virgin Islands 

National Park

Chief, Natural 

Resources

340-693-8950

x 224

Rafe_Boulon@nps.gov

Tim Connors NPS, Geologic Resources 

Division

GRI Mapping 

Coordinator

303-969-2093 Tim_Connors@nps.gov

Melanie Harris U.S. Geological Survey Geographer mharris@usgs.gov

Bruce Heise NPS, Geologic Resources 

Division

GRI Program 

Coordinator

303-969-2017 Bruce_Heise@nps.gov

Christy Loomis NPS, Virgin Islands 

National Park and Virgin 

Islands Coral Reef National 

Monument

Data Manager Christy_Loomis@nps.gov

Mark Monaco National Oceanographic 

and Atmospheric 

Administration

Biologist 301-713-3028

x 160

mark.monaco@noaa.gov

Kim N. Hall NPS, Virgin Islands 

National Park and Virgin 

Islands Coral Reef National 

Monument

Biological Science 

Technician

rosydog@hotmail.com

Matt Patterson NPS, South 

Florida/Caribbean Network

Inventory and 

Monitoring 

Coordinator

305-252-0347 Matt_Patterson@nps.gov

Doug Rankin U.S. Geological Survey Geologist 703-648-6903 dwrankin@usgs.gov
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 161/104872, July 2010 
National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 

1201 Oakridge Drive, Suite 150 

Fort Collins, CO 80525 

www.nature.nps.gov 

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