Monocacy National Battlefield 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2008/051 

National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 

Monocacy National Battlefield 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2008/051 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 

September 2008 

U.S. Department of the Interior 

Washington, D.C.

COVER: Visitor Center Creek, Monocacy National Battlefield 

INSIDE COVER: Thomas Farm Pond, Monocacy National Battlefield 

NPS Photos by National Capital Region Network Staff 
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the back cover. 

Please cite this publication as: 

Thornberry-Ehrlich, T. 2008. Monocacy National Battlefield Geologic Resource Evaluation 

Report. Natural Resource Report NPS/NRPC/GRD/NRR—2008/051. National Park Service, 

Denver, Colorado. 

NPS D-78, September 2008 
 MONO Geologic Resource Evaluation Report iii 

Table of Contents 

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

Executive Summary ...................................................................................................... 1

Introduction ................................................................................................................... 2

Purpose of the Geologic Resource Evaluation Program ............................................................................................2

History of Monacacy National Battlefield ....................................................................................................................2

Geologic Setting .........................................................................................................................................................2

Geologic Issues............................................................................................................. 6

Erosion and Slope Processes.....................................................................................................................................6

Sediment Load and Channel Storage.........................................................................................................................6

Water Issues...............................................................................................................................................................6

Recreational Demands ...............................................................................................................................................8

Soil .............................................................................................................................................................................9

Paleontology...............................................................................................................................................................9

Geology Education and Research..............................................................................................................................9

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

Geologic Setting and Military History of Monocacy National Battlefield....................................................................10

Flooding of the Monocacy River ...............................................................................................................................10

The Blue Ridge Anticlinorium and Frederick Valley..................................................................................................11

Caves and Karst Formation......................................................................................................................................11

Geology and Archaeology ........................................................................................................................................11

Historical Preservation..............................................................................................................................................12

Map Unit Properties .................................................................................................... 15

Map Unit Properties Table........................................................................................................................................16

Geologic History.......................................................................................................... 17

Glossary....................................................................................................................... 22

References................................................................................................................... 26

Appendix A: Geologic Map Graphic .......................................................................... 28

Appendix B: Scoping Summary................................................................................. 31

Attachment 1: Geologic Resource Evaluation Products CD 
iv NPS Geologic Resources Division 

List of Figures 

Figure 1. Map of Monocacy National Battlefield.............................................................................................................4

Figure 2. Location of Monocacy National Battlefield relative to geologic features..........................................................5

Figure 3. Regional map of Confederate Troop movement in 1864...............................................................................12

Figure 4. Map of Monocacy area showing troop movement during 1864 battle ...........................................................13

Figure 5. The Monocacy Aqueduct ..............................................................................................................................14

Figure 6. Monocacy Junction .......................................................................................................................................14

Figure 7: Geologic time scale.......................................................................................................................................20

Figure 8. Evolution of the landscape in the Monocacy area.........................................................................................21
 MONO Geologic Resource Evaluation Report 1 

Executive Summary 

This report accompanies the digital geologic map for Monocacy National Battlefield in 

Maryland, which the Geologic Resources Division produced in collaboration with its 

partners. It contains information relevant to resource management and scientific research. 

Monocacy National Battlefield is preserved to 

commemorate the men who fought on its soil in 1864 

during the American Civil War. The landscape reflects a 

unique geologic history that spans from the ancient 

Precambrian through the formation of the Appalachian 

Mountains, and from the more recent Ice Age events to 

the modern day. Every landscape is determined by its 

past and present underlying geologic structure. The 

landscape begins with the geology, and the processes that 

shaped today’s environments, history, and scenery. 

Knowledge of geologic resources can directly support 

resource management decisions that address geologic 

issues, air and water quality, urbanization, flood risk, 

wildlife populations, invasive species, future scientific 

research projects, and interpretive needs associated with 

the park. 

Geologic processes give rise to a landscape composed of 

rock formations, hills and valleys, waterfalls, and 

wetlands. This landscape played a prominent role in the 

movement of troops and battle locations during the Civil 

War. Local geology dictated the placement of bridges, 

fords, and railroads, which in turn informed military 

strategy. Today, geologic processes continue to develop a 

landscape that influences human use patterns. The 

connection between history and geology inspires visitors, 

and emphasis on geologic resources will enhance the 

visitor’s experience. 

The rocks of central Maryland reflect the powerful 

tectonic forces responsible for the Appalachian 

Mountains. Precambrian gneiss, metavolcanic rocks, and 

younger (Paleozoic) quartzite and phyllite underlie the 

hills visible to the west of Monocacy. The entire region 

was compressed during three separate tectonic events, 

the Taconic, Acadian, and Alleghenian orogenies. 

Following this compression, a series of fault-bounded 

extension basins, such as Frederick Valley, developed in 

the Triassic. These basins filled with sediment shed from 

the mountains. 

Humans have significantly modified the landscape of 

Monocacy by developing dams, trails, buildings and 

farms, roads, bridges and streamworks, as well as 

polluting the air and water. Geologic processes continue 

to change the landscape. The need to balance historic 

and natural preservation and restoration with recreation 

makes resource management a challenge. 

The following issues have geologic significance for 

management of the park: 

• Erosion and slope processes 

The relatively wet climate of the eastern United States, 

combined with severe storms, loose soils along slopes, 

and active streams at Monocacy National Battlefield, 

creates a setting that is especially susceptible to 

slumping, slope creep, and erosion of stream banks. 

Increased runoff can dramatically alter the landscape, 

creating new hazardous areas in the process, and may 

also clog streams with excess sediment, which affects 

hydrologic systems and aquatic life. 

• Sediment load and channel storage 

Erosion of the landscape at Monocacy leads to 

increases in the sediment carried by the rivers in the 

park. Sediment loads and distribution affect aquatic 

and riparian ecosystems (including drinking-water 

supplies). Sediment loading can result in changes to 

channel morphology and increased frequency of 

overbank flooding. Fine-grained sediments also serve 

to transport contaminants in a water system. 

• Water issues 

Floods are a natural process along many rivers, 

creating fertile floodplains and washing away 

accumulated debris. However, seasonal flooding of the 

Monocacy River threatens the historic context of the 

battlefield and surrounding areas. Protecting these 

features and cultural resources along the banks of the 

river requires an understanding of the relationships 

between geology, the hydrologic system, and biology 

throughout the park. 

Other geologic parameters and issues, such as 

recreational demands, water issues, agricultural 

pollution, and geologic education and research, have also 

been identified as critical management issues for 

Monocacy National Battlefield. These are described 

further in the Geologic Issues section of this report. 
2 NPS Geologic Resources Division 

Introduction 

The following section briefly describes the National Park Service Geologic Resource 

Evaluation Program and the regional geologic setting of Monocacy National Battlefield. 

Purpose of the Geologic Resource Evaluation Program 

The Geologic Resource Evaluation (GRE) Program is 

one of 12 inventories funded under the NPS Natural 

Resource Challenge designed to enhance baseline 

information available to park managers. The program 

carries out the geologic component of the inventory 

effort from the development of digital geologic maps to 

providing park staff with a geologic report tailored to a 

park’s specific geologic resource issues. The Geologic 

Resources Division of the Natural Resource Program 

Center administers this program. The GRE team relies 

heavily on partnerships with the U.S. Geological Survey, 

Colorado State University, state surveys, and others in 

developing GRE products. 

The goal of the GRE Program is to increase 

understanding of the geologic processes at work in parks 

and provide sound geologic information for use in park 

decision making. Sound park stewardship relies on 

understanding natural resources and their role in the 

ecosystem. Geology is the foundation of park 

ecosystems. 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 this goal, the GRE team is systematically 

working towards providing each of the identified 270 

natural area parks with a geologic scoping meeting, a 

digital geologic map, and a geologic report. These 

products support the stewardship of park resources and 

are designed for non-geoscientists. During scoping 

meetings the GRE team brings together park staff and 

geologic experts to review available geologic maps and 

discuss specific geologic issues, features, and processes. 

The GRE mapping team converts the geologic maps 

identified for park use at the scoping meeting into digital 

geologic data in accordance with their innovative 

Geographic Information Systems (GIS) Data Model. 

These digital data sets bring an exciting interactive 

dimension to traditional paper maps by providing 

geologic data for use in park GIS and facilitating the 

incorporation of geologic considerations into a wide 

range of resource management applications. The newest 

maps come complete with interactive help files. As a 

companion to the digital geologic maps, the GRE team 

prepares a park-specific geologic report that aids in use 

of the maps and provides park managers with an 

overview of park geology and geologic resource 

management issues. 

For additional information regarding the content of this 

report and up to date GRE contact information please 

refer to the Geologic Resource Evaluation Web site 

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

History of Monacacy National Battlefield 

Monocacy National Battlefield is located in Frederick 

County, Maryland. It was established as a National 

Memorial Park on June 21, 1934, and redesignated a 

National Battlefield on October 21, 1976, by an act of 

Congress in order to preserve and commemorate the 

sacrifices made during the American Civil War. 

The name Monocacy comes from the Shawnee name for 

the river “Monnockkesey” which means “river with 

many bends.” This winding river set the stage for the 

battle fought there in 1864. The 1864 Battle of Monocacy 

Junction was fought on the east bank of the Monocacy 

River on July 9, 1864, along what is now Maryland Route 

355. Union troops attempted to burn all bridges across 

the river, but the Confederates were able to cross late in 

the day. 

The landscape of the park consists of rolling hills and 

river valleys. Brooks Hill provides a scenic view of much 

of the battlefield area (fig. 1). Over this hill the 

Confederate attacks proceeded towards Union troops at 

the Thomas Farm. The attack stretched from the 

Monocacy River almost to Baker Valley Road to the 

southeast. Fighting continued over to Georgetown Pike, 

and the Union retreat crossed the Baltimore and Ohio 

(B&O) Railroad towards Baltimore. 

The boundaries of the park have changed several times 

since its beginning. Though created in the 1930s, land 

was not purchased until the 1980s and the park was not 

opened until 1991. The 1,647 acre park attracted 22,125 

visitors in 2007. In addition to its rich historical context, 

the park provides recreational opportunities and a 

sanctuary for many species in the urbanized Frederick 

area. 

Geologic Setting 

The geology affected the 1864 Battle of Monocacy 

Junction on regional and local levels. Two large rivers, 

the Monocacy and the Potomac, shaped the course of 

military movements in the area before the battles. Safe 

river crossings were vital to military success during the 

Civil War. 

The Monocacy River is the third largest tributary of the 

Potomac River. The free-flowing river is approximately 

93 km (58 mi) long and is fed by a drainage area of 

1,927 km2

 (744 mi2). The river begins at the confluence of 

Marsh Creek and Rock Creek in Adams County, 

Pennsylvania, and ends at its confluence with the 

Potomac near Dickerson, Maryland. Tributaries of the 

river in the battlefield area include Furnace Branch, 

Double Pipe Creek, and Stony Creek in Maryland and 

Tom’s Creek in Pennsylvania. 
 MONO Geologic Resource Evaluation Report 3 

The area’s smaller streams played a significant role in the 

actual fighting at Monocacy by creating important 

topographic differences and tactical targets such as 

railroad bridges, crossings, gaps, gulleys, and protective 

cover. On the gentle landscape of Monocacy, even the 

smallest swell or depression was utilized for tactical 

advantage. 

Monocacy National Battlefield is located east of the 

Catoctin Mountains, part of the northern end of the Blue 

Ridge, a physiographic subprovince of the Appalachian 

Mountains (fig. 2). Forming the easternmost part of the 

Blue Ridge province of Maryland and northern Virginia, 

the Catoctin Mountains are a belt of Lower Cambrian 

sediments and older metavolcanic rocks. The mountain 

ridge extends 80 km (50 mi) along a discontinuous linear 

trend from Emmitsburg, Maryland to Leesburg, Virginia. 

The park is in the Frederick Valley and is underlain by 

thick Triassic sediments just east of the Blue Ridge. The 

downdropped Frederick Valley is bordered on the west 

by a large normal fault. 

The following is a general description of several of the 

region’s physiographic provinces. 

Atlantic Coastal Plain Province 

The Atlantic Coastal Plain province is primarily flat 

terrain with elevations ranging from sea level to about 

100 m (300 ft) in northern Virginia. It extends from New 

York to Mexico. Sediments eroding from the 

Appalachian Highland areas to the west were 

intermittently deposited on the Atlantic Coastal Plain 

over the past 100 million years, forming a wedge-shaped 

sequence during periods of higher sea level. These 

deposits were then reworked by fluctuating sea levels 

and the continual erosive action of waves along the 

coastline. 

The Atlantic Coastal Plain province stretches from the 

Fall Line east to the Chesapeake Bay and Atlantic Ocean. 

The province continues as the submerged Continental 

Shelf province for another 120 km (75 mi) to the east. 

Atlantic Coastal Plain surface soils are commonly sandy 

or sandy-loams that are well-drained. Large streams and 

rivers in the Atlantic Coastal Plain province, including 

the James, York, and Potomac Rivers, are often 

influenced by tidal fluctuations. 

Piedmont Province 

The “Fall Line,” or “Fall Zone,” marks a transitional zone 

where the softer, less-consolidated sedimentary rocks of 

the Coastal Plain to the east intersect the harder, more 

resilient metamorphic rocks to the west to form an area 

of ridges and waterfalls and rapids. This zone covers 

more than 27 km (17 mi) of the Potomac River from 

Little Falls Dam, near Washington, D.C., west to Seneca, 

Maryland. Examples of this transition are present in the 

Potomac Gorge of the Chesapeake and Ohio Canal 

National Historic Park. Encompassing the Fall Line, 

westward to the Blue Ridge Mountains, is the Piedmont 

physiographic province. 

The eastward-sloping Piedmont Plateau was formed 

through a combination of folding, faulting, uplift and 

erosion. These processes resulted in an eastern landscape 

of gently rolling hills starting at 60 m (200 ft) in elevation 

that becomes gradually steeper towards the western edge 

of the province at 300 m (1,000 ft) above sea level. The 

Piedmont Plateau is composed of hard, crystalline 

igneous and metamorphic rocks such as schist, phyllite, 

slate, gneiss, and gabbro. 

Within the Piedmont are a series of Triassic extensional 

basins formed by normal faults during crustal extension. 

The faults opened basins (grabens) that were rapidly 

filled with roughly horizontal layers of sediment. 

Examples of these basins include the Frederick Valley, 

which hosts the park, and the Culpeper Valley of 

northern Virginia. 

Blue Ridge Province 

The Blue Ridge Province extends from Pennsylvania to 

Georgia along the eastern edge of the Appalachian 

Mountains. It contains the highest elevations in the 

Appalachian Mountain system in North Carolina, near 

Great Smoky Mountains National Park. Precambrian 

and Paleozoic igneous, sedimentary, and metamorphic 

rocks were uplifted during several mountain building 

events to form the steep, rugged terrain. Resistant 

Cambrian quartzite forms Blue Ridge, Bull Run 

Mountain, South Mountain, and Hogback Ridge in 

Virginia (Nickelsen 1956). South Mountain and Catoctin 

Mountain, both anticlines, are two examples of the 

pervasive folding in the Blue Ridge province. 

Eroding streams have caused the narrowing of the 

northern section of the Blue Ridge Mountains into a thin 

band of steep ridges, climbing to heights of 

approximately 1,230 m (4,000 ft). The Blue Ridge 

province is typified by steep terrain covered by thin, 

shallow soils, resulting in rapid runoff and low groundwater recharge rates. 

Valley and Ridge Province 

The landscape of the Ridge and Valley physiographic 

province is characterized by long, parallel ridges of 

resistant sandstone separated by valleys formed in more 

easily eroded shale and carbonate rocks. This province 

contains strongly folded and faulted sedimentary rocks 

in western Maryland. 

Areas dominated by carbonate formations exhibit karst 

topography. “Karst” is a term used to describe a region of 

irregular topography characterized by sinks, 

underground streams, caves, and springs formed by 

water percolating through water-soluble rock. 

The eastern part of the Ridge and Valley province is part 

of the Great Valley (Shenandoah Valley). It is connected 

to the Piedmont province by streams that cut through the 

Blue Ridge Mountains. 
4 NPS Geologic Resources Division 

Figure 1. Map of Monocacy National Battlefield. 
 MONO Geologic Resource Evaluation Report 5 

Figure 2. Location of Monocacy National Battlefield relative to geologic features of the Blue Ridge Province in Maryland. Note also the 

locations of the Piedmont and Valley and Ridge physiographic provinces. Graphic adapted from a figure in Whitaker (1955). 
6 NPS Geologic Resources Division 

Geologic Issues 

A Geologic Resource Evaluation scoping session was held for Monocacy National 

Battlefield on April 30−May 2, 2001, 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. 

Erosion and Slope Processes 

The topographic relief within and surrounding the park 

is small. However, the likelihood of landslides and 

slumps increases with precipitation and undercutting of 

slopes by streams, roads, trails, and other development. 

Landslide hazard models and maps could help park 

managers assess specific areas relative risk for landslide 

occurance. These tools use information about geology, 

topology, and climate to identify hazardous areas. 

Severe weather is difficult to predict. The Monocacy 

National Battlefield area of Maryland can receive large 

amounts of snow (e.g., 208 cm [82 in] in 1996) and is in a 

hurricane-affected zone. Periodic flooding of the 

Monocacy River results from sudden, large inputs of 

precipitation. Extreme weather combined with moderate 

slopes and loose, unconsolidated soils and substrate can 

lead to sudden, catastrophic slope failures. On slopes 

that lack stabilizing vegetation, rock and soil may 

mobilize and slide downhill, resulting in a massive slump 

or debris flow. In the vicinity of streams and rivers, this 

leads to shoreline erosion, increased sediment load, 

gullying, and the threat of destruction for trails, bridges, 

and other features of interest. 

Increased erosion along the outer banks of bends in 

streambeds (where stream velocity is higher) causes the 

bank to retreat, leading to undercutting and washout. 

Trees, trails, and other features along these banks are 

undermined. Trees fall across the stream, and trails are 

washed out. Remedial structures such as cribbing, log 

frame deflectors, jack dams, stone riprap, and/or log 

dams can shore up the bank, deflect the flow, and help to 

slow erosion (Means 1995). However, these same 

structures may have deleterious effects when used at 

inappropriate sites causing eddying and further 

degradation of the banks beyond the margins of the 

structures. 

Inventory, Monitoring, and Research Suggestions for 

Erosion and Slope Processes 

• Monitor unstable slopes and streambanks for hazards 

to staff and visitors. 

• Monitor erosion rates at key sites using repeated 

profile measurements. 

• Develop a landslide hazard map or model for the park. 

Sediment Load and Channel Storage 

Erosion at Monocacy leads to increases in sediment 

carried by the park’s rivers. Sediment loads and 

distribution affect aquatic and riparian ecosystems and 

can result in changes to channel morphology and 

increase overbank-flooding frequency. 

High suspended sediment load continues to be a 

management problem at Monocacy National Battlefield. 

Seasonal floods and storms can increase sediment load to 

levels unsuitable for drinking-water suppliers, causing 

occasional closure of drinking water-supplies upstream 

and increasing the need for chemical treatment in 

drinking water from the lower reaches of the watershed. 

(http://www.acb-online.org/pubs/projects/deliverables150-4-2003.pdf [Accessed August 2008]). 

However, fine-grained sediments are vital in the overall 

fluvial transport of contaminants in a water system. 

Channel storage of fine sediment (and the contaminants 

contained therein) follows a seasonal cycle. This cycle is 

subject to hydrologic variability, with increased 

availability during the high stands of spring and 

decreased availability during the low stands of autumn. 

Fine-grained sediments do not travel downstream in a 

single pulse, but are often resuspended bottom material 

(Miller et al. 1984). This intermittent transport of 

contaminants and fine-grained sediment increases the 

affected area and could pose a threat to the park if 

focused, severe contamination were to occur within the 

Monocacy River Basin in Maryland. 

Inventory, Monitoring, and Research Suggestions for 

Sediment Load and Channel Storage 

• Study channel morphology of intense seasonal runoff. 

Consult professional geomorphologists about 

erosional processes. 

• Inventory morphological characteristics of channels 

and monitor changes. 

• Encourage reforestation along the Monocacy River to 

act as a buffer to erosion and to filter incoming 

nutrients and pollution. 

Water Issues 

In the humid eastern climate of Maryland, water seems 

present everywhere in streams, rivers, runoff, springs, 

and groundwater wells. Annual precipitation at 

Monocacy National Battlefield averages ≈97 cm (38 in) 

per year with almost half of the rain coming in the 

summer months during short intense storms. Because of 

the development of the surrounding areas, water 

resources are under constant threat of contamination 

and overuse. The most severe threats to park streams are 

from impacts of existing and future development in the 

rapidly growing Frederick area. The population of the 
 MONO Geologic Resource Evaluation Report 7 

Monocacy watershed increased 55% between 1970 and 

1990 alone (http://www.hood.edu/academic/biology/ 

monocacy/Watershed/monocacy_watershed.htm 

[Accessed July 2005]). 

Anthropogenic effects from road salts, runoff from 

impervious surfaces, septic systems, tilled fields, 

agricultural and residential fertilizers, pesticides, and 

herbicides, animal waste, overuse, and acid rain can 

considerably alter groundwater chemistry (Trombley 

and Zynjuk 1985; Dyer and Logan 1995). As 

suburbanization of the entire region increases, a decrease 

in agriculture and an increase in residential activites will 

lead to growth in landscaping-derived chemical input (L. 

McClelland 2005, personal communication). 

The preservation of the integrity of the watershed is a 

major management objective at Monocacy and for the 

City of Frederick (the Monocacy is the principal water 

resource for the city) (www.cityoffrederick.com/ 

departments/Planning [Accessed July 2005]). Local 

groups advocating a Riverbank Buffer Plan have stirred 

controversy among landowners (Kunkle 2004). 

The integrity of the watershed is directly reflected in the 

quality of the river water. Differences in water quality 

stem from a variety of natural and non-natural sources. 

For instance, major geochemical differences exist 

between water sampled from areas underlain by different 

lithologic units as controlled by hydrolysis, or the 

process that controls the chemical composition of most 

natural waters (Bowser and Jones 2002). Studies stress 

the importance of knowing the mineral compositions of 

both the aqueous phase and the host rock. 

Ground-water chemistry in silicate-dominated rocks 

seems particularly sensitive to compositions of 

plagioclase (albite), smectite (clay), and mafic minerals 

(mica, amphibole, and pyroxene), whereas the presence 

of quartz or potassium feldspar has very little effect 

(Logan and Kivimaki 1998; Bowser and Jones 2002). 

Similarly, it was determined that vein calcite and 

dolomite contribute calcium to the system and that 

chlorite contributes magnesium (Logan and Dyer 1996). 

Many of these minerals contributing to chemical 

variations of groundwater are present in the map units 

within and surrounding Monocacy. 

The hydrogeologic system at Monocacy National 

Battlefield is dominated by a karst aquifer. Karst features 

are formed by the dissolution of carbonate rocks such as 

limestone and dolomite. Karst aquifers can be highly 

permeable. In tests of mass-balance models in the area, 

Field and Mose (1998) determined that the median 

conduit apertures ranged from 1.16–1.24 m (3.80–4.07ft). 

Median macrofissures (narrower than conduits) ranged 

from 5.53–5.88 cm (2.18–2.31 in.). This implies rapid flow 

of groundwater through the aquifer after rainstorms, 

reducing the capacity of the substrate to filter impurities 

from the groundwater. 

The hydrogeologic system changes in response to 

increased surface runoff as well. This increase is a result 

of the further development of impervious surfaces, such 

as parking lots, roads, and buildings. Sedimentation also 

increases due to clearing land for development and water 

temperature increases because of the insulating nature of 

impervious surfaces. However, base flows of streams 

decrease because impervious surfaces prevent infiltration 

into the aquifer. Thus, the difference between base and 

peak streamflows typically increases as a consequence of 

development in the absence of runoff mitigation 

measures, such as detention ponds. 

Where agricultural runoff, construction materials, and 

other human pollutants are present, nitrogen (and other 

contaminant) levels in the water may reach dangerous 

levels. Runoff from roadways commonly contains high 

levels of oil and other car emissions that are carried into 

park waterways and seep into the soil. Salt used to keep 

roads clear of snow and ice in winter contaminates soil 

along ditches. Knowledge of the chemicals used in 

regional agriculture and development, combined with an 

understanding of the hydrogeologic system, including 

groundwater flow patterns, is essential to protect the 

ecosystem of the watershed for the park. 

The movement of nutrients and contaminants through 

the hydrogeologic system can be modeled by monitoring 

the composition of system inputs, such as rainfall, and 

outputs, such as streamflow. Other input sources include 

wind, surface runoff, ground-water transport, sewage 

outfalls, landfills, and fill dirt. Streams in effect integrate 

the surface runoff and ground-water flow of their 

watersheds. Thus, they provide a measure of the status 

forthe watershed’s hydrologic system. Consistent 

measurement of these parameters is crucial to 

establishing baselines for comparison. 

Flooding Issues 

Much of Monocacy National Battlefield comprises 

floodplains along the Monocacy River. The visitor center 

and surrounding fields are often flooded during sudden 

and seasonal high stands. This flooding has damaged 

foundations of buildings and electrical wiring and has 

affected crops in surrounding fields. The floodplain of 

the Monocacy River is described in greater detail in the 

following Features and Processes section. 

Agricultural Pollution 

The Monocacy River is categorized as a Maryland Wild 

and Scenic River (passed by the Maryland General 

Assembly in 1968, Monocacy River inclusion April 30, 

1974). However, it has one of the greatest non-point 

source pollution problems in the region, largely due to 

agricultural runoff. Agriculture combined with easily 

eroded soil has the potential to degrade both surface and 

groundwater. 

By increasing nutrient levels such as nitrogen and 

phosphorous, introducing other agrichemicals, and 

increasing suspended sediment, agricultural practices 

pose a serious threat to the Monocacy watershed and by 

extension the Potomac River and Chesapeake Bay 

systems. 

The Environmental Protection Agency rated the 

Monocacy watershed (Hydrologic Unit Code 2070009) a 
8 NPS Geologic Resources Division 

3 overall on a scale of 1–6 for water quality. This score 

indicates moderately serious water-quality problems 

with aquatic conditions below state goals 

(http://www.hood.edu/academic/biology/monocacy/Wa

tershed/monocacy_watershed.htm [Accessed July 

2005]). 

As much as 60% of the watershed is dedicated to 

agricultural use on the fertile soils of the Frederick 

Valley, including large areas of Monocacy National 

Battlefield. About 33% remains forested (mixed-oak 

deciduous forest). Urban areas such as Frederick, 

Maryland, complete the watershed. More than 3,500 

farms, dairies, and livestock operations contribute 

polluting runoff and eroded sediment to the system 

(http://www.acb-online.org/pubs/projects/deliverables150-4-2003.pdf [Accessed August 2008]). 

The U.S. Department of Agriculture, as well as the 

Maryland Department of Agriculture, is addressing this 

problem in a water-quality demonstration project 

designed to help reduce degradation from agricultural 

operations. Improved water quality depends upon better 

farming techniques, termed Best Management Practices 

(BMPs), which should address nutrient and agrichemical 

use as well as soil conservation in the area. 

Across the watershed, soil erosion from open fields 

ranges from 2–35 tons of soil per acre per year. This 

affects the land surrounding Monocacy National 

Battlefield as well as the river flowing through it. The Tvalue (a measure of how much soil can be eroded and 

still maintain agricultural productivity) is a mere 3 tons 

per acre per year throughout the watershed. Erosion 

control is needed to improve productivity as well as 

preserve the watershed (http://www.acbonline.org/pubs/projects/deliverables-150-4-2003.pdf 

[Accessed August 2008]). 

Runoff from nearby farms combined with all septic 

systems enrich nutrients in the Monocacy watershed. 

Livestock operations produce nearly 1,119,400 tons of 

manure containing the equivalent of 4,400 tons of 

nitrogen and 900 tons of phosphorous. Inorganic 

nitrogen fertilizer use has increased more than four-fold 

since 1960. Pesticide use has tripled since 1964. Fecal 

coliform, an indicator of disease-causing organisms in 

water, has been a persistent problem for the section of 

river below the Frederick Sewage Treatment plant, very 

close to Monocacy National Battlefield (http://www.acbonline.org/pubs/projects/deliverables-150-4-2003.pdf 

[Accessed August 2008]). 

Geologic and climatic factors play a significant role in the 

overall condition and health of the watershed. 

Precipitation, slope, soil type, soil permeability, and 

water-recharge rates all significantly affect the amount of 

nitrogen and other pollutants leached below plant root 

zones. The overall pollution problem is complicated by 

properties such as solubility and absorption rate. Once 

the contaminant moves below the soil and into the 

underlying karst aquifer, little chance for filtering exists 

in the highly permeable substrate. Karst terrane 

commonly has interconnected conduits, and water 

typically moves rapidly through the system. 

Pilot programs in which farmers utilized BMPs have 

produced promising results for the Monocacy 

conservation projects. In 1991, 42 demonstration plots 

resulted in reduced soil erosion on land covering 3,500 

acres. Erosion was reduced by an average of 6 tons of soil 

per acre per year. This early work prevented nearly 5,600 

tons of sediment from flowing into the targeted streams 

(Israel Creek, Piney/Alloway Creeks, and Linganore 

Creek). More farmers are being invited to join the 

incentives program. 

In 2007 the NPS Water Resources Division (WRD) 

completed a Water Resources Stewardship Report for 

Monocacy National Battlefield. The goal of this report is 

to develop comprehensive strategies for water resources 

that help the park achieve or maintain desired conditions 

using measurable and objective indicators. The report is 

available on the Web (http://www.nature.nps.gov/water/ 

planning/Stewardship_Reports/MONO_WRSR_final_pd

f.pdf) (Accessed September 2008). 

Inventory, Monitoring, and Research Suggestions for Water 

Issues 

• Work with the NPS WRD, the U.S. Geological Survey, 

and the Maryland Geological Survey to design and 

implement appropriate monitoring programs in the 

watershed. 

• Map and quantify subterranean recharge zones, 

focusing specifically on karst-related conduits. 

• Work with local officials to encourage development 

and maintenance of a buffer zone along the river to 

help protect the watershed by facilitating natural river 

processes. 

• Prepare educational exhibits explaining the natural 

processes of floods, including the benefits to soil 

fertility. 

• Reference - the Water Quality Inventory for 

Watershed Monocacy at the following EPA site: 

http://yosemite.epa.gov/water/adopt.nsf/c2e50050353

1739e85256a71005550c8/4a7150b0ee01226e85256f9c0

06c838c!OpenDocument (Accessed August 2008). 

• Reference - the Maryland Department of the 

Environment’s (MDE) list of documents regarding 

various conservation, restoration, and monitoring 

projects, as well as water quality, physical habitat 

condition, and other biological measures in the Lower 

Monocacy River watershed: 

http://mddnr.chesapeakebay.net/wsprofiles/surf/prof/

wsprof.cfm?watershed=02140302 (Accessed August 

2008). 

Recreational Demands 

Monocacy National Battlefield provides numerous 

recreational possibilities, including Civil War study, 

hiking, fishing, bicycling, picnicking, and photography. 

The park promotes activities that do not damage the 

park’s resources or endanger other visitors. 
 MONO Geologic Resource Evaluation Report 9 

The park receives many visitors, especially during the 

summer months; visitors totaled 22,125 in 2007. Visitors 

are placing increasing demands on the resources of the 

park. Management concerns vary from trail erosion to 

streambank erosion. 

Many trails wind through preserved biological, 

historical, and geologic environments at the park. Many 

of these are especially fragile, and off-trail hiking 

promotes their degradation. The park encourages 

recreation within designated trails and picnic areas. 

Prohibited use in non-designated areas increases the area 

of impact and places delicate ecosystems at risk. 

The Monocacy River enhances the natural beauty of the 

park. As with hiking, overuse of certain areas can lead to 

contamination and degradation of the ecosystem and 

increased erosion of stream banks. The Works Progress 

Administration (WPA) built stone walls in the 1930s to 

combat flooding along the Monocacy River. These and 

other efforts by the park have attempted to protect 

certain sensitive reaches of the river and locations near 

visitor areas. These supports are meant to reduce streambank erosion, but such measures are temporary. In 

addition to the large river and local streams (Bush Creek, 

Harding’s Run, among other unnamed tributaries), there 

are two manmade ponds in the park (on the Gambrill 

and Thomas Farms) intended to provide water for 

livestock. 

Inventory, Monitoring, and Research Suggestions for 

Recreational Demands 

• Design wayside exhibits to encourage responsible use 

of park resources. 

• Promote stabilizing vegetation along slopes at risk for 

slumping and erosion. 

• Promote topographic and geologic mapping in the 

park linked to recreational use patterns to determine 

areas at high risk for resource degradation. 

Soil 

The Soil Resources Inventory (SRI) Program of the NPS 

Geologic Resources Division partnered with the Natural 

Resources Conservation Service (NRCS) to complete a 

soil survey for Monocacy National Battlefield in 2005. 

The SRI Program provides user-friendly products to 

park managers to facilitate effective resource 

management, as well as baseline information on soil 

resources for the Vital Signs Monitoring Program. Soil 

resource inventories equip parks with maps showing the 

locations and extent of soils; data about the physical, 

chemical, and biological properties of those soils; as well 

as information regarding potential uses and limitations of 

each kind of soil type. The products also can be used for 

park interpretive programs and to identify emerging Soil 

Program needs. 

Paleontology 

Monocacy National Battlefield has not had a formal 

paleontological inventory and no paleontological 

material has been collected within the park. However, 

there may be potential for future fossil discoveries within 

the fossiliferous geologic formations exposed within the 

park (Kenworthy and Santucci 2004). 

The Araby Formation of early to mid Cambrian age, has 

yielded fragments of trilobite fossils from a location 

northeast of Monocacy National Battlefield. These are 

considered significant because they are among the oldest 

Piedmont fossils found in Maryland. The Rocky Springs 

Station Member of the Fredrick Formation (late 

Cambrian in age) has also produced trilobite fossils from 

a location northwest of the park (Kenworthy and 

Santucci 2004). 

Fossils are non-renewable resources that bring geologic 

history to life from an interpretive perspective and would 

require park protection if discovered. Scientific interest 

in the paleontology of Monocacy National Battlefield 

may afford the park an opportunity to partner with 

researchers and develop interpretive programs and 

materials explaining this aspect of the parks geologic 

history. 

Inventory, Monitoring, and Research Suggestions for 

Paleontology 

• Collaborate with the scientific community to 

investigate potential paleontological sites. 

• Be aware of formations containing potential fossil 

resources when planning infrastructure projects in the 

park. 

Geology Education and Research 

Monocacy National Battlefield has the opportunity to 

improve geologic interpretation by educating park 

visitors about role of geology in the environment and 

history. A detailed geologic map and a road or trail log, 

along with a guidebook linking Monocacy National 

Battlefield to the other parks in the Central Appalachian 

region would enhance a visitor’s appreciation of the 

geologic history and dynamic processes that created the 

natural landscape and played a role in the Civil War 

battle showcased at the park. Strategically placed 

wayside exhibits would also help explain the geology and 

the role that geology played in park history to visitors. 

Inventory, Monitoring, and Research Suggestions for 

Geology Education and Research 

• Research the surficial geologic story at Monocacy and 

develop an interpretive program to relate the current 

landscape, ecosystem, history, and biology to the 

geology. 
10 NPS Geologic Resources Division 

Geologic Features and Processes 

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

in Monocacy National Battlefield. 

Geologic Setting and Military History of Monocacy 

National Battlefield 

The Confederate army’s 2nd Corps, under the command 

of Lieutenant General Jubal A. Early, set out with 10,000 

men, 4,000 cavalry, and 40 guns towards Washington, 

D.C., from the Shenandoah Valley, crossing the Potomac 

at Shepherdstown, in June of 1864 (fig. 3). They were 

attempting to divert Union forces from the quagmire at 

Petersburg. Union Major General Lewis Wallace 

traveled west with a small force (≈5,000 men) to meet the 

Confederates. His defensive position was east of the 

Monocacy River, directly facing three bridges spanning 

the river (http://usa-civil-war.com/Monocacy/ 

monocacy.html [Accessed August 2008]). 

On July 9, the Confederates began crossing the river at a 

downstream ford to advance on the Union left flank (fig. 

4). The Battle of Monocacy Junction had begun. 

Approximately 2,400 men fell in the struggle also known 

as the “Battle that Saved Washington.” In the end, the 

Confederates won the day, diverting Union attention 

away from General Robert E. Lee’s forces at Petersburg, 

Virginia. However, the battle delayed the Confederate 

advance on Washington, D.C. Although they reached 

Fort Stevens within the city’s boundaries by July 12, 

Early’s troops were forced to retreat by the arrival of 

Union reinforcements to defenses around the capital city 

(www.nps.gov/mono). 

Geology played a vital role in military success and failure 

in the Battle of Monocacy Junction. In the area around 

Monocacy, the parallel valleys and ridges of the 

Piedmont, Blue Ridge, and Valley and Ridge 

physiographic provinces directed troop and supply 

movement along predictable routes. Gaps such as 

Thoroughfare Gap and Harper’s Ferry through the Blue 

Ridge were often the only means of crossing the 

mountains from east to west. These were strategic points 

to defend. Many early railroads and roads followed the 

trends of these natural geologic features. The confluence 

of several major roads and railroads at Monocacy 

Junction made it a focal point of defense from a southern 

approach towards Washington, D.C., or Baltimore. 

The Monocacy River, the third largest tributary of the 

Potomac River, was another obstacle to Confederate 

advancement. Union Major General Lew Wallace chose 

Monocacy Junction as the site of a battle to halt 

Confederate troops. The Georgetown Pike to 

Washington, the National Road to Baltimore, and the 

Baltimore and Ohio (B&O) Railroad all crossed the river 

in the area. These, in addition to the natural Worthington 

McKinney Ford, were strategic targets for the Union 

army to defend. 

During the battle, troops used natural features such as 

ridges, low valleys and depressions, shallow fords, 

undercut banks, and other subtle topographic 

expressions to their advantage and for defense. 

Interpretive materials could emphasize geologic controls 

during troop movements as a way of educating the public 

about the interconnectedness between history and 

science. A deeper understanding of the landscape would 

also result from such information. 

In cooperation with the Chesapeake & Ohio Canal 

Association, visitors may also be directed to the 

neighboring Monocacy Aqueduct, in nearby Chesapeake 

& Ohio Canal National Historical Park (fig. 5). The 

aqueduct is one of eleven along the canal. It is more than 

157 m (515 ft) in length and has seven arches constructed 

of white and pink quartz sandstone quarried nearby at 

Sugarloaf Mountain. Construction began in 1829 and 

ended in 1833. This feature is threatened by floods and 

large storms such as Hurricane Agnes in 1972 

(http://www.geocities.com/Yosemite/3524/monocacy.ht

ml [Accessed August 2008]). 

Flooding of the Monocacy River 

Floods bring to mind terrible disasters, lost property, and 

lost resources. However, floods are a natural process and 

are vital to soil formation in fertile floodplain areas. 

Floodplains are defined as areas of land adjacent to rivers 

that are covered in water on a regular basis during river 

high stands. Much of the Monocacy Battle was fought on 

the floodplain. In the 1800s most of the riverbank was 

cleared of buffering trees for agriculture. Encourageing 

native plant life along the river will help buffer the 

erosive nature of floods as well as absorb (in part) 

potentially harmful nutrients, waste, and sediments from 

nearby developments and fields. 

The U.S. Geological Survey measures the streamflow of 

the Monocacy at several locations. Hydrographs are 

available at the following website: 

http://md.water.usgs.gov/surfacewater/streamflow/ 

(Accessed August 2008). These hydrographs detail the 

location, drainage area, gage, station type, peak 

streamflow, daily streamflow, and contact information. 

According to the National Oceanic and Atmospheric 

Administration (NOAA), from 1929–2001 there were 86 

floods that reached a flood stage of 5 m (16 ft). This is 

almost one per year with the potential to cause serious 

damage to low-lying areas along the river’s edge 

(http://www.erh.noaa.gov/marfc/Rivers/FloodClimo/M

onths/pot/FrederickPOT.pdf [Accessed August 2008]). A 

minor flood was defined as a crest from 5–5.2 m (16–17 

ft), a moderate flood as 5.2–6 m (17–20 ft), and a major 

flood as greater than 6 m (20 ft) above normal flow. 
 MONO Geologic Resource Evaluation Report 11 

Near the park, the floodplain of the Monocacy River was 

the site of the original Moravian settlement in 

Bethlehem. Many historic buildings are located on the 

floodplain. As part of the New Deal program in the 1930s 

the Works Progress Administration program erected 

stonewalls along the Monocacy to prevent further flood 

damage (http://home.moravian.edu/users/phys/mejjg01/ 

geology/images/Flood_1955/bethlehem_flood_of_1955.h

tm [Accessed August 2008]). In addition to the park area, 

the City of Frederick maintains areas of parkland along 

the floodplain itself, but the entire area is poorly drained 

and prone to seasonal flooding. 

The Blue Ridge Anticlinorium and Frederick Valley 

The northern terminous of the Blue Ridge is north of 

Monocacy, in southern Pennsylvania. At this northern 

end, the Blue Ridge consists of a northeast-plunging, 

asymmetric anticlinorium, locally referred to as the 

South Mountain anticlinorium (trending N20E) (Logan 

and Dyer 1996). It extends southwestward nearly 400 km 

(250 mi) to the Roanoke, Virginia, area (Mitra 1989). 

Monocacy National Battlefield is east of the eastern, 

upright limb of the anticlinorium, also known as the 

Catoctin Mountains. The normal, eastern limb of the 

anticline at the Catoctin Mountains exhibits open folds 

that show uniform strains (Mitra 1976). 

The entire anticlinorium is locally overturned to the 

northwest. The west limb dips steeply southeast, the 

crest is broad and flat, and the east limb dips 

approximately 50 degrees southeast. The anticlinorium 

exposes Grenville granodiorite and granitic gneiss in its 

core and is flanked on each side by Precambrian and 

Lower Paleozoic metasedimentary and metavolcanic 

rocks (Mitra 1989). The Swift Run (phyllite and 

quartzite), Fauquier and Mechum River 

(metamorphosed clastic sedimentary rocks), and 

Catoctin (greenstone, metarhyolite, and metasediments) 

Formations unconformably overlie the Precambrian 

gneissic rocks in central Maryland and northern Virginia. 

The structural style of the anticlinorium is continuous 

across the Great Valley and into the Valley and Ridge 

province. The anticlinorium is associated with 

Alleghenian thrusting above a detachment that extends 

eastward into the Piedmont province (Onasch 1986). 

The anticlinorium marks the easternmost extent of the 

Blue Ridge province in Maryland. The structure at 

Catoctin Mountain is truncated on the east by a Triassic 

border fault. The fault separates the early Paleozoic 

rocks to the west from the thick Triassic rocks filling the 

Frederick Valley. The fault is largely covered by debris 

and sediments shed from the Catoctin Mountains 

highlands (Whitaker 1955). The fault was likely active 

during the Triassic extension that was responsible for 

many large, narrow, northeast-trending, down-faulted 

basins along the foothills of the Appalachians following 

the Alleghenian orogeny. The Culpeper Basin, south of 

Catoctin Mountain in Virginia, is another example of a 

Triassic extensional basin. 

Caves and Karst Formation 

Large carbonate deposits, including the Frederick 

Limestone, underlie the Frederick Valley. Carbonate 

rock dissolves in acidic meteoric water to form fissures. 

With increased water flow and subsequent dissolution, 

these fissures can expand into passages and ultimately 

hollow caverns and rooms. Outside the park, north of 

Frederick, the Monocacy River Cave is developed in 

thin-bedded Frederick Limestone. The cave is small, 

having an entrance 1.2 m (4 ft) wide and extending for 

another 8 m (26 ft). The cave is located above the east 

bank of the Monocacy River, east of Harrisonville. River 

alluvium that covers the floor of the cave demonstrates 

the role of the river in cave formation 

(http://www.mgs.md.gov/esic/features/cave/monoc.html

[Accessed August 2008]). 

The presence of even a small cave in nearby areas is 

evidence of karst development in the geologic units 

beneath Monocacy National Battlefield. The dissolution 

of carbonate rocks by ground water flowing through 

fissures, cracks, or joints creates karst terrain. The 

presence of karst has had a dramatic effect on the 

hydrogeology of the area. Because Frederick Limestone 

underlies the Monocacy River basin almost entirely, its 

hydrogeologic regime has probably been altered by the 

dissolution of the carbonate below. Karst terrain can 

include underground streams, springs, caves, sinkholes, 

and pinnacles. Sinkholes are developed throughout most 

of the carbonate rock formations in the area. The karst 

features around Monocacy National Battlefield have not 

yet been inventoried. 

Karst landforms, like sinkholes and caves, occur 

elsewhere in the Frederick Valley area, including in the 

Great Valley, the Valley and Ridge, the Culpeper basin, 

and Westminster terrane in the western Piedmont 

province. These areas have abundant limestone, 

dolomite, and marble rock units (Southworth et al. 

2001). Karst is rare in the Blue Ridge province to the west 

because marble occurs only as small bodies. 

Karst occurs in three different sections of the Piedmont 

province. Kanawha Spring, just east of Point of Rocks, 

flows from the limestone of the Frederick Formation, 

which underlies the flood plain. Limestone cobbles 

within the conglomerate of the Leesburg Member of the 

Balls Bluff Siltstone dissolve to form hummocky 

topography with abundant sinkholes and springs just 

southeast of Point of Rocks. In addition, marble and 

limestone rock units of the Westminster terrane 

(exposed along Monocacy River north of Indian Flats) 

underlie linear valleys. These form abundant sinkholes to 

the north. 

Geology and Archaeology 

Long before Confederate and Union troops converged 

on the Monocacy area during the Civil War, people had 

been using the area’s abundant natural resources for 

hunting and farming. Hunting tools and animal 

(mastodon) teeth in Frederick County record local 

ancient Native American activity. Early settlers, in the 

mid 1600’s, reported an Indian hunting camp northwest 

of Frederick (Means 1995). The area provided the Native 

Americans with materials for tools, animals for food and 

clothing, and a variety of nuts, berries and other plants 

for gathering. 
12 NPS Geologic Resources Division 

The thick, rich soils shed from the highlands to the west 

and deposited in the floodplains, as well as an abundant 

annual water supply, attracted settlers and farmers to the 

area. This interest continues today with local agricultural 

comprising the bulk of the Monocacy watershed. 

Historical Preservation 

One of the major goals of the park is to preserve the 

historical context of the area; this includes preserving 

and restoring old buildings and the landscape around 

them. Maintaining this landscape often means resisting 

natural geologic changes, which presents several 

management challenges. For example, a proposal for 

restoration of a historic building may consist of removing 

surrounding natural materials. The streams in the park 

are also sometimes engineered to preserve fishing habitat 

and protect trails, buildings, and streambanks from being 

undercut. These efforts attempt to reverse many natural 

geologic changes. 

Geologic slope processes such as landsliding, slumping, 

chemical weathering, and slope creep are constantly 

changing the landscape at the park. Runoff erodes 

sediments from any open areas and carries them down 

streams and gullies. Historic structures and subtle 

topographic features are all vulnerable to change due to 

the geologic processes of weathering and erosion. 

Erosion naturally diminishes higher areas and fills in the 

lower areas and in the process distorts the historical 

context of the landscape. The park’s goal of preserving 

both the natural and historical context of the area is 

constantly compromised by the continuous natural 

processes of erosion and weathering as well as local 

urban development. 

Intense storms such as Hurricane Isabel in September 

2003 damaged many local historical features, including 

the Beatty-Kramer House, Derr House, the Visitor 

Center at Monocacy National Battlefield, cabins at 

Catoctin Mountain Park, and the Chesapeake and Ohio 

Canal National Historical Park 

(www.marylandhistoricaltrust.net/isabel_event_FR.html

[Accessed July 2005]). 

The history of the area is heavily influenced by its 

geology. The geology determined the local river 

crossings and fords, and localized construction of 

railroad grades (fig. 6). 

Figure 3. Regional map showing the path that Lieutenant General Jubal A. Early’s troops followed towards Washington, D.C. in the 

summer of 1864. 
 MONO Geologic Resource Evaluation Report 13 

Figure 4. Map of Monocacy area showing troop movement during 1864 battle. Gray arrows indicate Confederate forces. Blue arrows 

indicate Union forces. Note location of Monocacy Junction, the Worthington McKinney Ford, and Gambrill’s Mill (modern Visitor 

Center). 
14 NPS Geologic Resources Division 

Figure 5. The Monocacy Aqueduct, which carries the Chesapeake and Ohio Canal over the Monocacy River. Photograph by Robert 

Kroll (1964). 

Figure 6. Monocacy Junction (circle). This was the center of the Union infantry skirmish line. Photograph courtesy of: http://usa-civilwar.com/Monocacy/monocacy.html. 
 MONO Geologic Resource Evaluation Report 15 

Map Unit Properties 

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

Evaluation digital geologic map of Monocacy National Battlefield. The accompanying 

table is highly generalized and is provided for background purposes only. Grounddisturbing 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 Monocacy 

National Battlefield informed the “Geologic History,” 

“Geologic Features and Processes,” and “Geologic 

Issues” sections of this report. Geologic maps are 

essentially two-dimensional representations of complex 

three-dimensional relationships. The various colors on 

geologic maps represent rocks and unconsolidated 

deposits. Bold lines that cross and separate the color 

patterns mark structural features such as faults and folds. 

Point symbols indicate features such as dipping strata, 

sample localities, mine features, wells, and cave openings. 

Incorporation of geologic data into a geographic 

information system (GIS) increases the utility of geologic 

maps and clarifies spatial relationships to 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 do not show 

soil types and are not soil maps, but they do show parent 

material, a key factor in soil formation. Furthermore, 

resource managers have used geologic maps to make 

correlations between geology and biology. For instance, 

geologic maps have served as tools for locating 

threatened and endangered plant species. 

Although geologic maps do not show where future 

earthquakes will occur, the presence of a fault indicates 

past movement and possible future seismic activity. 

Geologic maps will not show where the next landslide, 

rockfall, or volcanic eruption will occur, but mapped 

deposits show areas that have been susceptible to such 

geologic hazards. Geologic maps do not show 

archaeological or cultural resources, but past peoples 

may have inhabited or been influenced by various 

geomorphic features that are shown on geologic maps. 

As examples alluvial terraces may preserve artifacts, and 

inhabited alcoves may occur at the contact between two 

rock units. 

The features and properties of the geologic units in the 

following table correspond to the accompanying digital 

geologic data. Map units are listed from youngest to 

oldest. Please refer to the geologic time scale (fig. 7) for 

the age associated with each time period. This table 

highlights characteristics of map units such as 

susceptibility to hazards; the occurrence of fossils, 

cultural resources, mineral resources, and caves; and the 

suitability as habitat or for recreational use. The 

following are source data for the GRE digital geologic 

map: 

Southworth, S., and D. Denenny. 2006. Geologic map of 

the national parks in the National Capital Region, 

Washington D.C., Virginia, Maryland and West 

Virginia. Scale 1:24,000. Open-File Report OF 2005-

1331. Reston, VA: U.S. Geological Survey. 

Using ESRI ArcGIS software, the Geologic Resource 

Evaluation team created a digital geologic map from this 

source. GRE digital geologic-GIS map products include 

data in ESRI personal geodatabase and shapefile GIS 

formats, layer files with feature symbology, FGDC 

metadata, a Windows HelpFile that contains all of the 

ancillary map information and graphics, and an ESRI 

ArcMap map document file that easily displays the map, 

and connects the HelpFile directly to the map document. 

GRE digital geologic data are included on the attached 

CD and are available through the NPS Data Store 

(http://science.nature.nps.gov/nrdata/). The surficial 

map units in the Monocacy National Battlefield area 

include and overlie rocks of the western Piedmont 

province. These rocks include late Proterozoic and 

Lower Cambrian metasedimentary rocks of the 

Chilhowee Group (Loudoun, Weverton, Harpers, and 

Antietam Formations), which consist of 

metaconglomerate, phyllite, quartzite, shale, and slate. 

Other map units in the area are Lower and Middle 

Cambrian metasedimentary rocks and Upper Cambrian 

to Lower Ordovician carbonate rocks of the Frederick 

Valley synclinorium, including the Tomstown Dolomite 

and the Frederick and Grove Limestones (Southworth 

and Brezinski 2003). 

The area is part of the Triassic extensional basin formed 

by down-dropped block faulting to the west. Upper 

Triassic sedimentary rocks of the Newark Group and 

early Jurassic diabase sills and dikes fill the basin. The 

Gettysburg Shale and New Oxford Formation lie within 

several Triassic extensional basins as part of the Newark 

Group. The scant diabase sills and dikes are late 

remnants of tectonic extension and renewed igneous 

activity in the area. 

Lining river and stream valleys are unconsolidated highand low-level alluvial terrace gravels, alluvial gravel, 

sand, and silt, and residual gravel. Other recent deposits 

include colluvial slope deposits such as talus and slump 

deposits (Southworth and Brezinski 2003). These 

Quaternary units cover the landscape at Monocacy 

National Battlefield. 

 MONO Geologic Resource Evaluation Report 17 

Geologic History 

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

geologic map of Monocacy National Battlefield, the environment in which those units 

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

Monocacy National Battlefield is located in the 

Frederick extensional valley just east of the ridge that 

forms the boundary between the Blue Ridge and 

Piedmont physiographic provinces in central Maryland. 

As such, it contains features that are intimately tied with 

the long geologic history of the Appalachian Mountains 

and the evolution of the eastern coast of the North 

American Continent. A regional perspective is presented 

here to connect the landscape and geology of the park to 

its surroundings. 

The recorded history of the Appalachian Mountains 

begins in the Proterozoic (fig. 7). In the mid-Proterozoic, 

during the Grenville orogeny, a supercontinent formed 

that consisted of most of the continental crust in 

existence at that time, including North America and 

Africa. Sedimentation, deformation, plutonism, and 

volcanism are all manifested in the metamorphic granite 

and gneiss in the core of the modern Blue Ridge 

Mountains (Harris et al. 1997). 

These rocks formed over a period of a 100 million years 

and are more than a billion years old, making them 

among the oldest rocks known in this region. They were 

later uplifed and thus exposed to erosive forces for 

hundreds of millions of years. Their leveled surface 

forms a basement upon which all other rocks of the 

Appalachians were deposited (Southworth et al. 2001). 

At Monocacy National Battlefield, these ancient rocks 

are buried beneath the Catoctin Mountains to the west, 

but they are exposed in the Blue Ridge south of the park 

(Means 1995). 

The late Proterozoic, roughly 800−600 million years ago 

(Ma), brought extensional rifting to the area. The crustal 

extension created fissures through which massive 

volumes of basaltic magma were extruded (fig. 8A). This 

volcanic activity lasted tens of millions of years and 

alternated between flood-basalt flows and ash falls. The 

volcanic rocks covered the granitic and gneissic 

basement in the Catoctin Mountains area. 

Because of the tensional tectonic forces, the 

supercontinent broke up and a sea basin formed that 

eventually became the Iapetus Ocean. This basin 

subsided and collected many of the sediments that later 

formed the Appalachian Mountains (fig. 8B). 

Some of the sediments were deposited as alluvial fans, 

large submarine landslides and turbidity flows, which 

today preserve their depositional features. These early 

sediments are exposed on Catoctin Mountain, Short 

Hill−South Mountain, the Blue Ridge−Elk Ridge, and in 

areas within and surrounding Monocacy as the 

Chilhowee Group (Loudoun Formation, Weverton 

Formation, Harpers Formation, and Antietam 

Formation) (Southworth et al. 2001). 

Associated with the shallow marine setting along the 

eastern continental margin of the Iapetus were large 

deposits of sand, silt, and mud in near-shore, deltaic, 

barrier-island, and tidal-flat areas. Some of these are 

present in the Chilhowee Group in Central Maryland, 

including the Harpers Formation and the Antietam 

Formation (Schwab 1970; Kauffman and Frey 1979; 

Simpson 1991). In addition, huge masses of carbonate 

rocks, such as the Cambrian Tomstown Dolomite and 

Frederick Limestone, as well as the Upper Cambrian to 

Lower Ordovician Grove Limestone, were deposited 

atop the Chilhowee Group. They record a grand 

platform thickening to the east that persisted during the 

Cambrian and Ordovician Periods (545-480 Ma) and that 

forms the floors of Frederick and Hagerstown Valleys 

(Means 1995). 

Somewhat later, 540, 470, and 360 Ma, igneous 

granodiorite, pegmatite, and lamprophyre, respectively, 

intruded the sedimentary rocks. During several episodes 

of mountain building and continental collision 

(described below) the entire sequence of sediments, 

intrusive rocks, and basalt were deformed and 

metamorphosed into schist, gneiss, marble, slate, and 

migmatite (Southworth et al. 2000). 

Taconic Orogeny 

From Early Cambrian through Early Ordovician time 

orogenic activity along the eastern margin of the 

continent began again. The Taconic orogeny (≈440−420 

Ma in the central Appalachians) was a volcanic 

arc−continent convergence. Oceanic crust and the 

volcanic arc from the Iapetus basin were thrust onto the 

eastern edge of the North American continent. The 

Taconic orogeny resulted in the closing of the ocean, 

subduction of oceanic crust during the creation of 

volcanic arcs within the disappearing basin, and the 

uplift of continental crust (Means 1995). 

Initial metamorphism of the igneous rocks of the 

Catoctin Mountains (Catoctin Formation) into 

metabasalt and metarhyolite, as well as the Chilhowee 

Group Rocks into quartzite and phyllite, occurred during 

this orogenic event. 

In response to the overriding plate thrusting westward 

onto the continental margin of North America, the crust 

bowed downwards creating a deep basin that filled with 

mud and sand eroded from the highlands to the east (fig. 

8C) (Harris et al. 1997). This so-called Appalachian basin 

was centered on what is now West Virginia. These 

infilling sediments covered the grand carbonate platform 
18 NPS Geologic Resources Division 

and are today recorded by the shale of the Ordovician 

Martinsburg Formation (Southworth et al. 2001). 

During the Late Ordovician, the oceanic sediments of the 

shrinking Iapetus Ocean were thrust westward onto 

other deep-water sediments of the western Piedmont 

along the Pleasant Grove fault. Sediments that later 

became sandstone, shale, siltstone, quartzite, and 

limestone were then deposited in the shallow marine to 

deltaic environment of the Appalachian basin. These 

rocks, now metamorphosed, currently underlie the 

Valley and Ridge province west of Monocacy National 

Battlefield (Fisher 1976). 

Shallow marine to fluvial sedimentation continued for a 

period of about 200 million years during the Ordovician 

through Permian Periods, resulting in thick layers of 

sediments. Their source was the highlands that were 

rising to the east during the Taconian orogeny 

(Ordovician) and the Acadian orogeny (Devonian). 

Acadian Orogeny 

The Acadian orogeny (≈360 Ma) continued the mountain 

building of the Taconic orogeny as the African continent 

drifted toward North America (Harris et al. 1997). 

Similar to the preceding Taconic orogeny, the Acadian 

event involved collision of land masses, mountain 

building, and regional metamorphism (Means 1995). 

This event was focused north of central Maryland. 

Alleghenian Orogeny 

Following the Acadian orogeny, the proto-Atlantic 

Iapetus Ocean closed during the Late Paleozoic as the 

North American and African continents collided. This 

collision formed the Pangaea supercontinent and the 

Appalachian mountain belt still evident today. This 

mountain-building episode, termed the Alleghenian 

orogeny (≈325−265 Ma), is the last major orogeny that 

affected the Appalachians (fig. 8D) (Means 1995). The 

rocks were deformed by folds and faults producing the 

Sugarloaf Mountain anticlinorium and the Frederick 

Valley synclinorium in the western Piedmont, the Blue 

Ridge−South Mountain anticlinorium (including the 

Catoctin Mountains), and the numerous folds of the 

Valley and Ridge province (Southworth et al. 2001). 

During this orogeny, rocks of the Great Valley, Blue 

Ridge, and Piedmont provinces were transported along 

the North Mountain fault as a massive block (Blue 

Ridge−Piedmont thrust sheet) westward onto younger 

rocks of the Valley and Ridge. The amount of crustal 

shortening was very large. Estimates of 20−50 percent 

shortening would amount to 125–350 km (80−220 mi) 

(Harris et al. 1997). 

Deformed rocks in the eastern Piedmont were also 

folded and faulted, and existing thrust faults were 

reactivated as both strike-slip and thrust faults during the 

Alleghenian orogeny (Southworth et al. 2001). 

Paleoelevations of the Alleghenian Mountains are 

estimated at approximately 6,000 m (20,000 ft), 

analogous to the modern-day Himalaya Range in Asia. 

These mountains have been beveled by erosion to 

elevations of less than 600 m (2,000 ft) west of Monocacy 

National Battlefield (Means 1995). 

Triassic Extension to the Present 

Following the Alleghenian orogeny, during the late 

Triassic, a period of rifting began as the deformed rocks 

of the joined continents broke apart from about 230–200 

Ma. The supercontinent Pangaea was segmented into 

roughly the same continents that persist today. This 

episode of rifting, or crustal fracturing, initiated the 

formation of the current Atlantic Ocean and created 

many block-fault basins with accompanying volcanism 

(fig. 8E) (Harris et al. 1997; Southworth et al. 2001). 

The Newark Basin system is a large component of this 

tectonic setting. Large streams carried debris shed from 

the uplifted Blue Ridge and Piedmont provinces creating 

alluvial fans at their mouths. These were deposited as 

non-marine mud and sand in fault-created troughs, such 

as the Frederick Valley in central Maryland and the 

Culpeper basin in the western Piedmont of central 

Virginia. Many of these rift openings became lacustrine 

basins and were filled with thick deposits of silt and sand. 

Large faults, such as the border fault west of Monocacy 

National Battlefield, running beneath Thurmont and 

Catoctin Furnace, Maryland, formed the western 

boundaries of the basins and provided an escarpment 

that was quickly covered with eroded debris. Magma was 

intruded into the new sandstone and shale strata as sills 

(sub-horizontal sheets) and nearly vertical dikes that 

extend beyond the basins into adjacent rocks. 

After this magma was emplaced approximately 200 Ma, 

the region underwent a period of slow uplift and erosion. 

The uplift was in response to isostatic adjustments within 

the crust, which forced the continental crust upwards 

and exposed it to erosion. 

Thick deposits of unconsolidated gravel, sand, and silt 

were shed from the eroded mountains. These were 

deposited at the base of the mountains as alluvial fans 

and spread eastward becoming part of the Atlantic 

Coastal Plain (Duffy and Whittecar 1991; Whittecar and 

Duffy 2000; Southworth et al. 2001). The amount of 

material that was deposited has been inferred from the 

now-exposed metamorphic rocks to have been immense. 

Many of the rocks exposed at the surface must have been 

at least 20 km (≈10 mi) below the surface prior to 

regional uplift and erosion. Today, the Potomac, 

Rappahannock, Rapidan, and Shenandoah Rivers and 

tributaries continue to erode the Coastal Plain sediments, 

lowering the mountains, and depositing alluvial terraces 

along the rivers, as they sculpt the present landscape. 

Since the breakup of Pangaea and the uplift of the 

Appalachian Mountains, the North American plate has 

continued to drift toward the west. Isostatic adjustments 

that uplifted the continent after the Alleghanian orogeny 

continued at a lesser rate throughout the Cenozoic 

Period (Harris et al. 1997). 

The landscape and geomorphology of the greater 

Potomac and Rappahannock River valleys are the result 
 MONO Geologic Resource Evaluation Report 19 

of erosion and deposition from about the middle of the 

Cenozoic Period (≈5Ma) to the present. The distribution 

of flood plain alluvium and ancient fluvial terraces of the 

rivers and adjacent tributaries reflect the historical 

development of both drainage systems. There is little or 

no evidence that the rivers migrated laterally across a 

broad, relatively flat region. It seems the rivers have cut 

downward through very old, resistant rocks, 

overprinting their early courses (Southworth et al. 2001). 

Though glaciers from the Pleistocene Ice Ages never 

reached the central Maryland area (the southern 

terminus was in northeastern Pennsylvania), the colder 

climates of the Ice Ages played a role in the formation of 

the landscape at Monocacy National Battlefield. The 

periglacial conditions that must have existed near the 

glaciers intensified weathering and other erosional 

processes (Harris et al. 1997). Glacially influenced 

landforms and deposits are probably late Tertiary to 

Quaternary, when a wetter climate, sparse vegetation, 

and frozen ground caused increased precipitation to run 

into the ancestral river channels, enhancing downcutting 

and erosion by waterways (Means 1995; Zen 1997a and 

1997b). 
20 NPS Geologic Resources Division 

Figure 7: Geologic time scale; adapted from the U.S. Geological Survey (http://pubs.usgs.gov/fs/2007/3015/). Red lines indicate major 

unconformities between eras. Included are major events in life history and tectonic events occurring on the North American continent. 

Absolute ages shown are in millions of years(Ma, or mega-annum). 
 MONO Geologic Resource Evaluation Report 21 

Figure 8. Evolution of the landscape in the area of Monocacy National Battlefield from the Precambrian through the present. Graphic 

adapted from Means (1995). Drawings not to scale. 
22 NPS Geologic Resources Division 

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://wrgis.wr.usgs.gov/docs/parks/misc/glossarya.html. 

active margin. A continental margin where significant 

volcanic and earthquake activity occurs; commonly a 

convergent plate margin. 

alluvial fan. A fan-shaped deposit of sediment that 

accumulates where a high-gradient stream flows out of 

a mountain front into an area of lesser gradient, such 

as a valley. 

alluvium. Stream-deposited sediment that is generally 

rounded, sorted, and stratified. 

angular unconformity. An unconformity where the strata 

above and below are oriented differently; generally 

caused by structural deformation and erosion prior to 

deposition of the upper bed. 

anticlinorium. A composite anticlinal structure of 

regional extent composed of lesser folds. 

aquifer. Rock or sediment that are sufficiently porous, 

permeable, and saturated to be useful as a source of 

water. 

ash (volcanic). Fine pyroclastic material ejected from a 

volcano (also see “tuff”). 

asthenosphere. Weak layer in the upper mantle below 

the lithosphere where seismic waves are attenuated. 

basement. The undifferentiated rocks, commonly 

igneous and metamorphic, that underlie the rocks of 

interest. 

basin (structural). A doubly-plunging syncline in which 

rocks dip inward from all sides (also see “dome”). 

basin (sedimentary). Any depression, from continental 

to local scales, into which sediments are deposited. 

bed. The smallest sedimentary strata unit, commonly 

ranging in thickness from one centimeter to a meter or 

two and distinguishable from beds above. 

bedding. Depositional layering or stratification of 

sediments. 

bedrock geology. The geology of underlying solid rock 

as it would appear with the sediment, soil, and 

vegetative cover stripped away. 

block (fault). A crustal unit bounded by faults, either 

completely or in part. 

braided stream. A stream, clogged with sediment that 

forms multiple channels that divide and rejoin. 

calcareous. A rock or sediment containing calcium 

carbonate. 

carbonaceous. A rock or sediment with considerable 

carbon, especially organics, hydrocarbons, or coal. 

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”). 

chemical weathering. The dissolution or chemical 

breakdown of minerals at Earth’s surface via reaction 

with water, air, or dissolved substances. 

clastic. Rock or sediment made of fragments or preexisting rocks. 

clay. Clay minerals or sedimentary fragments the size of 

clay minerals (>1/256 mm). 

cleavage (rock). The tendency of rock to break along 

parallel planes that correspond to the alignment of 

platy minerals. 

concordant. Strata with contacts parallel to the attitude 

of adjacent strata. 

conglomerate. A coarse-grained sedimentary rock with 

clasts larger than 2 mm in a fine-grained matrix. 

continental crust. The type of crustal rocks underlying 

the continents and continental shelves; having a 

thickness of 25−60 km (16−37 mi) and a density of 

approximately 2.7 grams per cubic centimeter. 

continental drift. The concept that continents have 

shifted in position over Earth (see and use “plate 

tectonics”). 

continental rise. Gently sloping region from the foot of 

the continental slope to the abyssal plain. 

continental shelf. The shallowly submerged part of a 

continental margin extending from the shoreline to the 

continental slope with water depths of less than 200 m 

(656 ft). 

continental shield. A continental block of Earth’s crust 

that has remained relatively stable over a long period 

of time and has undergone only gentle warping 

compared to the intense deformation of bordering 

crust 

continental slope. The relatively steep slope from the 

outer edge of the continental shelf down to the more 

gently sloping ocean depths of the continental rise or 

abyssal plain. 

convergent boundary. A plate boundary where two 

tectonic plates are moving together (i.e., a zone of 

subduction or obduction). 

craton. The relatively old and geologically stable interior 

of a continent (also see “continental shield”). 

cross-bedding. Uniform to highlyvaried sets of inclined 

sedimentary beds deposited by wind or water that 

indicate distinctive flow conditions. 

cross section. A graphical interpretation of geology, 

structure, and/or stratigraphy in the third (vertical) 

dimension based on mapped and measured geological 

extents and attitudes depicted in an oriented vertical 

plane. 

crust. The outermost compositional shell of Earth, 10−40 

km (6−25 mi) thick, consisting predominantly of 

relatively low-density silicate minerals (also see 

“oceanic crust” and “continental crust”). 

crystalline. Describes the structure of a regular, orderly, 

repeating geometric arrangement of atoms 

debris flow. A rapid and often sudden flow or slide of 

rock and soil material involving a wide range of types 

and sizes. 

deformation. A general term for the process of faulting, 

folding, shearing, extension, or compression of rocks 

as a result of various Earth forces. 

delta. A sediment wedge deposited at a stream’s mouth 

where it flows into a lake or sea. 
 MONO Geologic Resource Evaluation Report 23 

dike. A tabular, discordant igneous intrusion. 

dip. The angle between a structural surface and a 

horizontal reference plane measured normal to their 

line of intersection. 

disconformity. An unconformity at which the bedding of 

the strata above and below are parallel. 

discordant. Having contacts that cut across or are set an 

angle to the orientation of adjacent rocks. 

divergent boundary. A tectonic plate boundary where 

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

continental rift zone). 

drainage basin. The total area from which a stream 

system receives or drains precipitation runoff. 

eustatic. Relates to simultaneous worldwide rise or fall 

of sea level in Earth’s oceans. 

evaporite. Chemically precipitated mineral(s) formed by 

the evaporation of solute-rich water under restricted 

conditions. 

exfoliation. The breakup, spalling, peeling, flaking, etc., 

of layers or concentric sheets from an exposed rock 

mass due to differential stresses resulting from thermal 

changes or pressure unloading. 

extrusion. The emission of relatively viscous lava onto 

the Earth’s surface; also, the rock so formed. 

extrusive. Of or pertaining to the eruption of igneous 

material onto the surface of Earth. 

facies (metamorphic). The pressure-temperature regime 

that results in a particular, distinctive metamorphic 

mineralogy (i.e., a suite of index minerals). 

facies (sedimentary). The depositional or environmental 

conditions reflected in the sedimentary structures, 

textures, mineralogy, fossils, etc. of a sedimentary 

rock. 

fault. A subplanar break in rock along which relative 

movement occurs between the two sides. 

formation. Fundamental rock-stratigraphic unit that is 

mappable and lithologically distinct from adjoining 

strata and has definable upper and lower contacts. 

fracture. Irregular breakage of a mineral; also any break 

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

frost wedging. The breakup of rock due to the expansion 

of water freezing in fractures. 

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

physical processes, components, and morphology. 

igneous. Refers to a rock or mineral that originated from 

molten material; one of the three main classes or 

rocks—igneous, metamorphic, and sedimentary. 

intrusion. A body of igneous rock that invades older 

rock. The invading rock may be a plastic solid or 

magma that pushes its way into the older rock. 

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

and parallel to a subduction zone. 

isostasy. The process by which the crust “floats” at an 

elevation compatible with the density and thickness of 

the crustal rocks relative to underlying mantle. 

isostatic adjustment. The shift of the lithosphere of the 

Earth to maintain equilibrium among units of varying 

mass and density; excess mass above is balanced by a 

deficit of density below, and vice versa. 

joint. A semi-planar break in rock without relative 

movement of rocks on either side of the fracture 

surface. 

karst topography. Topography characterized by 

abundant sinkholes and caverns formed by the 

dissolution of calcareous rocks. 

lacustrine. Pertaining to, produced by, or inhabiting a 

lake or lakes. 

lamination. The finest stratification or bedding as seen in 

shale and siltstone (syn: lamina or laminae) or the 

formation of laminae. 

landslide. Any process or landform resulting from rapid 

mass movement under relatively dry conditions. 

lava. Magma that has been extruded out onto Earth’s 

surface, both molten and solidified. 

levees. Raised ridges lining the banks of a stream; may be 

natural or artificial. 

limbs. The two sides of a structural fold on either side of 

its hingeline. 

lineament. Any relatively straight surface feature that can 

be identified via observation, mapping, or remote 

sensing, commonly representing tectonic features. 

lithification. The conversion of sediment into solid rock. 

lithology. The description of a rock or rock unit, 

especially the texture, composition, and structure of 

sedimentary rocks. 

lithosphere. The relatively rigid outmost shell of Earth’s 

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

encompasses the crust and uppermost mantle. 

loess. Silt-sized sediment deposited by wind, generally of 

glacial origin. 

mafic. A rock, magma, or mineral rich in magnesium and 

iron. 

magma. Molten rock generated within the Earth that is 

the parent of igneous rocks. 

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

core. 

matrix. The fine-grained interstitial material between 

coarse grains in porphyritic igneous rocks and poorly 

sorted clastic sediments or rocks. 

meanders. Sinuous lateral curves or bends in a stream 

channel. 

mechanical weathering. The physical breakup of rocks 

without change in composition (syn: physical 

weathering). 

member. A lithostratigraphic unit with definable contacts 

that subdivides a formation. 

metamorphic. Pertaining to the process of 

metamorphism or to its results. 

metamorphism. Literally, “change in form.” 

Metamorphism occurs in rocks through mineral 

alteration, genesis, and/or recrystallization from 

increased heat and pressure. 

mid-ocean ridge. The continuous, generally submarine, 

seismic, median mountain range that marks the 

divergent tectonic margin(s) in the world’s oceans. 

mineral. A naturally occurring, inorganic crystalline solid 

with a definite chemical composition or compositional 

range. 

mud cracks. Cracks formed in clay, silt, or mud by 

shrinkage during subaerial dehydration. 

nonconformity. An erosional surface preserved in strata 

in which crystalline igneous or metamorphic rocks 

underlie sedimentary rocks. 

normal fault. A dip-slip fault in which the hanging wall 

moves down relative to the footwall. 
24 NPS Geologic Resources Division 

obduction. The process by which the crust is thickened 

by thrust faulting at a convergent margin. 

oceanic crust. Earth’s crust formed at spreading ridges 

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

km (3−mi) thick and generally of basaltic composition. 

orogeny. A mountain-building event, particularly a wellrecognized event in the geological past (e.g., the 

Laramide orogeny). 

outcrop. Any part of a rock mass or formation that is 

exposed or “crops out” at Earth’s surface. 

overbank deposits. Alluvium deposited outside a stream 

channel during flooding. 

paleogeography. The study, description, and 

reconstruction of the physical geography from past 

geologic periods. 

paleontology. The study of the life and chronology of 

Earth’s geologic past based on the phylogeny of fossil 

organisms. 

Pangaea. A theoretica, single supercontinent that existed 

during the Permian and Triassic Periods (also see 

“Laurasia” and “Gondwana”). 

parent (rock). The original rock from which a 

metamorphic rock or soil was formed. 

passive margin. A tectonically quiet continental margin 

indicated by little volcanic or seismic activity. 

pebble. Generally, small, rounded rock particles from 4 

to 64 mm in diameter. 

permeability. A measure of the ease or rate that fluids 

move through rocks or sediments. 

plateau. A broad, flat-topped topographic high of great 

extent and elevation above the surrounding plains, 

canyons, or valleys (both land and marine landforms). 

plate tectonics. The theory that the lithosphere is broken 

up into a series of rigid plates that move over Earth’s 

surface above a more fluid aesthenosphere. 

pluton. A body of intrusive igneous rock. 

plutonic. Describes igneous rock intruded and 

crystallized at some depth in the Earth. 

porosity. The proportion of void space (cracks, 

interstices) in a volume of a rock or sediment. 

Principal of Original Horizontality. The concept that 

sediments are originally deposited in horizontal layers 

and that deviations from the horizontal indicate postdepositional deformation. 

Principle of Superposition. The concept that sediments 

are deposited in layers, one atop another, i.e., the rocks 

on the bottom are oldest with the overlying rocks 

progressively younger toward the top. 

progradation. The seaward building of land area due to 

sedimentary deposition. 

provenance. A place of origin. The area from which the 

constituent materials of a sedimentary rock were 

derived. 

radioactivity. The spontaneous decay or breakdown of 

unstable atomic nuclei. 

radiometric age. An age in years determined from 

radioisotopes and their decay products. 

recharge. Infiltration processes that replenish 

groundwater. 

red beds. Sedimentary strata composed largely of 

sandstone, siltstone, and shale that are predominantly 

red due to the presence of ferric oxide (hematite) 

coating individual grains. 

regression. A long-term seaward retreat of the shoreline 

or relative fall of sea level. 

relative dating. Determining the chronological 

placement of rocks, events, fossils, etc. from geological 

evidence. 

reverse fault. A contractional, high-angle (>45o), dip-slip 

fault in which the hanging wall moves up relative to the 

footwall (also see “thrust fault”). 

rift valley. A depression formed by grabens along the 

crest of an oceanic spreading ridge or in a continental 

rift zone. 

ripple marks. The undulating, subparallel, usually smallscale ridge pattern formed on sediment by the flow of 

wind or water. 

rock. A solid, cohesive aggregate of one or more minerals 

or mineraloids. 

roundness. The relative amount of curvature of the 

“corners” of a sediment grain, especially with respect 

to the maximum radius of curvature of the particle. 

sandstone. Clastic sedimentary rock of predominantly 

sand-sized grains. 

scarp. A steep cliff or topographic step resulting from 

vertical displacement on a fault or by mass movement. 

seafloor spreading. The process by which tectonic plates 

diverge and new lithosphere is created at oceanic 

ridges. 

sediment. An eroded and deposited, unconsolidated 

accumulation of lithic and mineral fragments. 

sedimentary rock. A consolidated and lithified rock 

consisting of detrital and/or chemical sediment(s). 

sequence. A major informal rock-stratigraphic unit that 

is traceable over large areas and defined by a major sea 

level transgression-regression sediment package. 

shale. A clastic sedimentary rock made of clay-sized 

particles that exhibit parallel splitting properties. 

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay (1/256−1/16 

mm). 

siltstone. A variablely lithified sedimentary rock 

composed of silt-sized grains. 

slickenside. A smoothly polished and commonly striated 

surface representing deformation of a fault plane. 

slope. The inclined surface of any geomorphic feature or 

rational measurement thereof (syn: gradient). 

slump. A generally large, coherent mass movement with 

a concave-up failure surface and subsequent backward 

rotation relative to the slope. 

soil. Surface accumulation of weathered rock and 

organic matter capable of supporting plant growth and 

commonly overlying the parent rock from which it 

formed. 

spring. A site where water flows out at the surface due to 

the water table intersecting the ground surface. 

strata. Tabular or sheetlike masses or distinct layers (e.g., 

of rock). 

stratigraphy. The geologic study of the origin, 

occurrence, distribution, classification, correlation, 

age, etc. of rock layers, especially sedimentary rocks. 

stream. Any body of water moving under gravity flow 

and confined within a channel. 

strike. The compass direction of the line of intersection 

that an inclined surface makes with a horizontal plane. 

strike-slip fault. A fault with measurable offset where the 

relative movement is parallel to the strike of the fault. 
 MONO Geologic Resource Evaluation Report 25 

subduction zone. A convergent plate boundary where 

oceanic lithosphere descends beneath a continental or 

oceanic plate and is carried down into the mantle. 

subsidence. The gradual sinking or depression of part of 

Earth’s surface. 

suture. The linear zone where two continental 

landmasses become joined due to obduction. 

syncline. A fold of which the core contains the 

stratigraphically younger rocks; it is generally concave 

upward. 

synclinorium. A composite synclinal structure of regional 

extent composed of lesser folds. 

tectonic. Relating to large-scale movement and 

deformation of Earth’s crust. 

tectonics. The geological study of the broad structural 

architecture and deformational processes of the 

lithosphere and aesthenosphere (also see “structural 

geology”). 

terraces (stream). Step-like benches surrounding the 

present floodplain of a stream due to dissection of 

previous flood plain(s), stream bed(s), and/or valley 

floor(s). 

terrane. A region or group of rocks with similar geology, 

age, or structural style. 

terrestrial. Relating to Earth or Earth’s dry land. 

theory. A hypothesis that has been rigorously tested 

against further observations or experiments to become 

a generally accepted tenet of science. 

thrust fault. A contractional, dip-slip fault with a 

shallowly dipping fault surface (<45o

) where the 

hanging wall moves up and over relative to the 

footwall. 

topography. The general morphology of Earth’s surface 

including relief and location of natural and 

anthropogenic features. 

trace (fault). The exposed intersection of a fault with 

Earth’s surface. 

trace fossils. Sedimentary structures, such as tracks, 

trails, burrows, etc., that preserve evidence of 

organisms’ life activities, rather than the organisms 

themselves. 

transgression. Landward migration of the sea due to a 

relative rise in sea level. 

trend. The direction or azimuth of elongation of a linear 

geological feature. 

type locality. The geographic location where a 

stratigraphic unit is well displayed, is formally defined 

as a typical section, and derives its name. 

unconformity. A surface within sedimentary strata that 

marks a prolonged period of nondeposition or 

erosion. 

uplift. A structurally high area in the crust, produced by 

movement that raises the rocks. 

volcanic. Related to volcanoes; describes igneous rock 

crystallized at or near Earth’s surface (e.g., lava). 

water table. The upper surface of the saturated (phreatic) 

zone. 

weathering. The set of physical, chemical, and biological 

processes by which rock is broken down in place. 
26 NPS Geologic Resources Division 

References 

This section lists references cited in this report as well as a general bibliography that may 

be of use to resource managers. A more complete geologic bibliography is available from 

the National Park Service Geologic Resources Division. 

Blomquist, J. D., and G. T. Fisher. 1994. Nitrogen sources 

and nitrate loads in major watersheds of the upper 

Potomac River basin. Eos, Transactions, American 

Geophysical Union 75 (16, Suppl.): 165. 

Bowser, C. J., and B. F. Jones. 2002. Mineralogic controls 

on the composition of natural waters dominated by 

silicate hydrolysis. American Journal of Science 302 (7): 

582−662. 

Duffy, D. F., and G. R. Whittecar. 1991. Geomorphic 

development of segmented alluvial fans in the 

Shenandoah Valley, Stuarts Draft, Virginia. Geological 

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Dyer, L. J., and W. S. Logan. 1995. Water-rock 

interaction and anthropogenic effects within the 

western Catoctin Mountain watershed, western 

Maryland. Geological Society of America Abstracts with 

Programs 27 (2): 51. 

Field, M. S., and D. G. Mose. 1998. Estimating subsurface 

fissure apertures in karst aquifers from equilibrium 

activities. Environmental & Engineering Geoscience 4 

(2): 145−159. 

Fisher, G. T. 1995. Selected herbicides in major streams 

in the Potomac River basin upstream from 

Washington, D.C. Fact Sheet FS 95-107. Reston, VA: 

U. S. Geological Survey. 

Fisher, G. T., and T. M. Lewis. 1990. Estimation of 

drainage density and overland flow length using digital 

cartographic data. In Application of geographic 

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P.Mason. 111−120. Blacksburg, VA: Virginia 

Polytechnic Institute and State University. 

Fisher, G. W. 1976. The geologic evolution of the 

northeastern Piedmont of the Appalachians. Geological 

Society of America Abstracts with Programs 8 (2): 

172−173. 

Harris, A. G., E. Tuttle, and S. D. Tuttle. 1997. Geology of 

National Parks. [place of publication]: Kendall/Hunt 

Publishing Company. 

Kauffman, M. E., and E. P. Frey. 1979. Antietam 

sandstone ridges; exhumed barrier islands or faultbounded blocks? Geological Society of America 

Abstracts with Programs 11 (1): 18. 

Kulp, R. R., and R. O. Hughes III. 1999. The existence of 

olivine in several exposures of Pennsylvania York 

Haven type diabase. Geological Society of America 

Abstracts with Programs 31 (7): 165. 

Kulp, R. R., and R. O. Hughes III. 2001, Xenoliths of the 

Triassic Passaic Formation in the Monocacy Hill 

diabase intrusion, Amity Township, Berks County, 

Pennsylvania. Geological Society of America Abstracts 

with Programs 33 (6): 375. 

Kunkle, F. 2004, Riverbank buffer plan angers 

landowners. Washington Post, May 23. 

Logan, W. S., and L. J. Dyer. 1996. Influence of mineral 

weathering reactions, road salt and cation exchange on 

groundwater chemistry, Catoctin Mountain, central 

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Programs 28 (7): 31−32. 

Logan, W. S., and K. W. Kivimaki. 1998. Mass-balance 

modeling of dissolved solutes in groundwater of 

metasediments and basin fill sediments, eastern 

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Conservation Service. 

Means, J. 1995. Maryland’s Catoctin Mountain parks; an 

interpretive guide to Catoctin Mountain Park and 

Cunningham Falls State Park. Blacksburg, VA: 

McDonald & Woodward Publishing Company. 

Miller, A. J., J. A. Smith, and L. L. Shoemaker. 1984. 

Channel storage of fine-grained sediment in the 

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Mitra, G. 1989. Day four; The Catoctin Mountain−Blue 

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 MONO Geologic Resource Evaluation Report 27 

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28 NPS Geologic Resources Division 

Appendix A: Geologic Map Graphic 

The following page is a snapshot of the geologic map for Monocacy National Battlefield. 

For a poster-size PDF of this map or for digital geologic map data, please see the 

included CD or visit the Geologic Resource Evaluation publications Web page 

(http://www.nature.nps.gov/geology/inventory/gre_publications). 
 MONO Geologic Resource Evaluation Report 31 

Appendix B: Scoping Summary 

The following excerpts are from the GRE scoping summary for Monocacy National 

Battlefield. The scoping meeting was on April 30–May 2, 2001; therefore, the contact 

information and Web addresses referred to in this appendix may be outdated. Please 

contact the Geologic Resources Division for current information. 

Executive Summary 

Geologic Resource Evaluation (GRE) workshops were 

held for National Park Service (NPS) Units in the 

National Capital Region (NCR) over April 30-May 2, 

2001. The purpose was to view and discuss the park’s 

geologic resources, to address the status of geologic 

mapping for compiling both paper and digital maps, and 

to assess resource management issues and needs. 

Cooperators from the NPS Geologic Resources Division 

(GRD), Natural Resources Information Division 

(NRID), individual NPS units in the region, and the 

United States Geological Survey (USGS) were present for 

the workshop. 

This involved half-day field trips to view the geology of 

Catoctin Mountain Park, Harpers Ferry NHP, Prince 

William Forest Park, and Great Falls Park, as well as 

another full-day scoping session to present overviews of 

the NPS Inventory and Monitoring (I&M) program, the 

GRD, and the ongoing GRE. Round-table discussions 

involving geologic issues for all parks in the National 

Capital Region included the status of geologic mapping 

efforts, interpretation, paleontologic resources, sources 

of available data, and action items generated from this 

meeting. 

Geologic Mapping 

- Existing Geologic Maps and Publications 

After the bibliographies were assembled, a separate 

search was made for any existing surficial and bedrock 

geologic maps for the National Capital Region parks. 

The bounding coordinates for each map were noted and 

entered into a GIS to assemble an index geologic map. 

Separate coverages were developed based on scales 

(1:24,000, 1:100,000, etc.) available for the specific park. 

Numerous geologic maps at varying scales and vintages 

cover the area. Index maps were distributed to each 

workshop participant during the scoping session. 

- Status 

The index of published geologic maps is a useful 

reference for the NCR. However, some of these maps are 

dated and are in need of refinement, and in other places, 

there is no existing large-scale coverages available. The 

USGS began a project to map the Baltimore-Washington, 

D.C., area at 1:100,000 scale, and as a result it was 

brought to their attention that modern, large-scale 

geologic mapping for the NCR NPS areas would be 

beneficial to NPS resource management. 

Because of this, the USGS developed a proposal to remap the NCR at large scale (1:24,000 or greater) and to 

supply digital geologic databases to accompany this 

mapping. Scott Southworth (USGS-Reston, VA) is the 

project leader and main contact. The original PMIS 

(Project Management Information Systems) statement is 

available as number 60900; of note is that portions of it 

need to be changed to reflect that the source of funding 

will be Inventory and Monitoring funds and not NRPP. 

-Desired Enhancements 

To better facilitate the geologic mapping, Scott 

Southworth would like to obtain better topographic 

coverage for each of the NCR units. Tammy Stidham 

knows that some of these coverages are already available 

and will supply them to Scott and the USGS. In general, 

anything in Washington, D.C., proper has 1-meter 

topographic coverage, and Prince George's county has 

1:24,000 coverage. 

Notes on Monocacy National Battlefield 

Monocacy (MONO) is lumped with Antietam; should 

have topographic coverage soon. Have occasional flood 

problems. 

Digital Geologic Map Coverage 

The USGS will supply digital geology in ArcInfo format 

for all of the NCR parks. GRE staff will take this data and 

add the Windows help file and NPS theme manager 

capability to the digital geology and will supply to the 

region to distribute to each park in NCR. 

Other Desired Data Sets for NCR 

Soils 

Pete Biggam (GRD Soil Scientist) supplied the following 

information in reference to soils for parks: 

National Capitol Parks - Central is covered by the 

"District of Columbia" Soil Survey (State Soil Survey 

Area ID MD099). It has been mapped, and is currently 

being refined to match new imagery. An interim digital 

product is available to us via NRCS, but the "final 

certified" dataset most likely will not be available until 

FY03. 

National Capitol Parks - Eastern is covered by portions 

of three soil survey areas; "District of Columbia 

(MD099),” "Charles County, Maryland (MD017),” and 

"Prince George's County, Maryland (MD033).” Both 

Charles County and Prince George's County are 

currently being updated, with Charles County scheduled 

to be available sometime in calendar year 2002, and 

Prince George's County sometime within calendar year 

2003. 

Paleontology 

Greg McDonald (GRD Paleontologist) would like to see 

an encompassing, systematic paleontological inventory 

for the NCR describing the known resources in all parks 
32 NPS Geologic Resources Division 

with suggestions on how to best manage these resources. 

In addition to the parks containing paleo resources in 

NACE, according to his current database, the following 

are considered "paleo parks" in the NCR: 

• Chesapeake & Ohio Canal NHP 

• George Washington Memorial Parkway 

• Manassas NBP 

• Prince William Forest Park 

• Harpers Ferry NHP 

Geologic Report 

A stand-alone encompassing report on each park’s 

geology is a major focus of the GRE. As part of the USGS 

proposal to map the NCR, they will be summarizing the 

major geologic features of each park in a report to 

accompany their database. 

It was suggested hoped that after the individual reports 

are finished a regional physiographic report will be 

completed for the entire NCR. 

List of Attendees for NPS National Capital Region Workshop 

NAME AFFILIATION PHONE E-MAIL 

Joe Gregson NPS, NRID (970) 225-3559 Joe_Gregson@nps.gov 

Tim Connors NPS, GRD (303) 969-2093 Tim_Connors@nps.gov 

Bruce Heise NPS, GRD (303) 969-2017 Bruce_Heise@nps.gov 

Lindsay McClelland NPS, GRD 202-513-7185 Lindsay_mcclelland@nps.gov 

Scott Southworth USGS (703) 648-6385 Ssouthwo@usgs.gov 

Pete Chirico USGS 703-648-6950 Pchirico@usgs.gov 

Pat Toops NPS, NCR 202-342-1443, ext. 212 Pat_toops@nps.gov 

James Voigt NPS, CATO 301-416-0536 Cato_resource_management@nps.gov 

Marcus Koenen NPS, NCR 202-342-1443, ext. 216 Marcus_koenen@nps.gov 

Ellen Gray NPS, NCR 202-342-1443, ext. 223 Ellen_gray@nps.gov 

Dale Nisbet NPS, HAFE 304-535-6770 Dale_nisbet@nps.gov 

Suzy Alberts NPS, CHOH 301-714-2211 Susan_alberts@nps.gov 

Dianne Ingram NPS, CHOH 301-714-2225 Dianne_ingram@nps.gov 

Bill Spinrad NPS, CHOH 301-714-2221 William_spinrad@nps.gov 

Debbie Cohen NPS, ANTI 301-432-2243 Debbie_cohen@nps.gov 

Ed Wenschhof NPS, ANTI/MONO 301-432-2243 Ed_wenschhof@nps.gov 

Ann Brazinski NPS, GWMP 703-289-2541 Ann_brazinski@nps.gov 

Melissa Kangas NPS, GWMP 703-289-2542 Melissa_Kangas@nps.gov 

Barbara Perdew NPS, GWMP 703-285-2964 Barbara_Perdew@nps.gov 

Barry Wood NPS, GWMP 703-289-2543 Barry_wood@nps.gov 

Marie Sauter NPS, CHOH 301-714-2224 Marie_frias@nps.gov 

Carol Pollio NPS, PRWI 703-221-2176 Carol_pollio@nps.gov 

Duane DonnellyMorrison NPS, PRWI 703-221-6921 Duane_donnelly-morrison@nps.gov 

Diane Pavek NPS-NRS 202-342-1443, ext. 209 Diane_Pavek@nps.gov 

Chris Jones NPS-WOTR 703-255-1822 Christopher_Jones@nps.gov 

Doug Curtis NPS-NCR-NRS 202-342-1443, ext.228 Doug_Curtis@nps.gov 

Brent Steury NPS-NACE 202-690-5167 Brent_Steury@nps.gov 

Dave Russ USGS 703-648-6660 Druss@usgs.gov 

Tammy Stidham NPS-RTSC 202-619-7474 Tammy_stidham@nps.gov 

Dan Sealy NPS-GWMP 703-289-2531 Dan_Sealy@nps.gov 

Sue Salmons NPS-ROCR 202-426-6834, ext. 33 Sue_salmons@nps.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. 

Monocacy National Battlefield 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2008/051 

NPS D-78, September 2008 

National Park Service 

Director • Mary A. Bomar 

Natural Resource Stewardship and Science 

Associate Director • Bert Frost 

Natural Resource Program Center 

The Natural Resource Program Center (NRPC) is the core of the NPS Natural Resource Stewardship and 

Science Directorate. The Center Director is located in Fort Collins, with staff located principally in 

Lakewood and Fort Collins, Colorado and in Washington, D.C. The NRPC has five divisions: Air 

Resources Division, Biological Resource Management Division, Environmental Quality Division, Geologic 

Resources Division, and Water Resources Division. NRPC also includes three offices: The Office of 

Education and Outreach, the Office of Inventory, Monitoring and Evaluation, and the Office of Natural 

Resource Information Systems. In addition, Natural Resource Web Management and Partnership 

Coordination are cross-cutting disciplines under the Center Director. The multidisciplinary staff of NRPC 

is dedicated to resolving park resource management challenges originating in and outside units of the 

national park system. 

Geologic Resources Division 

Chief • Dave Steensen 

Planning Evaluation and Permits Branch Chief • Carol McCoy 

Credits 

Author • Trista Thornberry-Ehrlich

Review • Lindsay McClelland and Carol McCoy 

Editing • Diane Lane 

Digital Map Production • Stephanie O'Meara and Trista Thornberry-Ehrlich 

Map Layout Design • Andrea Croskrey
Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, CO 80225 

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

(303) 969-2090 

EXPERIENCE YOUR AMERICATM 

National Park Service 

U.S. Department of the Interior