A Tapestry of

Time and Terrain

Pamphlet to accompany

Geologic Investigations Series I–2720

U.S. Department of the Interior

U.S. Geological Survey

A Tapestry of

Time and Terrain

Pamphlet to accompany

Geologic Investigations Series I–2720

U.S. Department of the Interior

U.S. Geological Survey
This page left intentionally blank
A Tapestry of Time and Terrain

By José F. Vigil, Richard J. Pike, and David G. Howell

Pamphlet to accompany

Geologic Investigations Series I–2720
2

U.S. Department of the Interior

Bruce Babbitt, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

United States Government Printing Office: 2000

Reprinted with minor corrections: 2008

For additional copies please contact:

USGS Information Services

Box 25286

Denver, CO 80225

Text edited by Jane Ciener

Layout and design by Stephen L. Scott

Manuscript approved for publication, February 24, 2000

For more information about the USGS and its products:

Telephone: 1–888–ASK–USGS

World Wide Web: http://www.usgs.gov/
3

Introduction

Through computer processing and enhancement, we have 

brought together two existing images of the lower 48 states of 

the United States (U.S.) into a single digital tapestry. Woven 

into the fabric of this new map are data from previous U.S. 

Geological Survey (USGS) maps that depict the topography 

and geology of the United States in separate formats. The 

resulting composite is the most detailed and accurate portrait 

of the U.S. land surface and the ages of its underlying rock 

formations yet displayed in the same image. The new map 

resembles traditional 3-D perspective drawings of landscapes 

with the addition of a fourth dimension, geologic time, which 

is shown in color. This union of topographic texture with the 

patterns defined by units of geologic time creates a visual synthesis that has escaped most prior attempts to combine shaded 

relief with a second characteristic shown by color, commonly 

height above sea level (already implicit in the shaded relief). 

In mutually enhancing the landscape and its underlying temporal structure, this digital tapestry outlines the geologic story 

of continental collision and break-up, mountain-building, river 

erosion and deposition, ice-cap glaciation, volcanism, and 

other events and processes that have shaped the region over 

the last 2.6 billion years. The map and the many features described in this pamphlet are online at http://tapestry.usgs.gov.

The terrain

[Most terms that may be unfamiliar to a general readership are italicized where first mentioned]

One of this map’s two components is a digital shadedrelief image that shows the shape of the land surface by variations in brightness. The degree of light and dark artificially 

mimics the intensity of the Sun’s light on different types of 

topography. This technique, called chiaroscuro, dates back 

some 400 years to sketches of the Tuscan landscape by Leonardo da Vinci. Because manual (artistic) portrayals of terrain 

can practicably show only small areas both accurately and in 

detail (Raisz, 1931), the technique has been automated by the 

computer to cover large regions. The resulting digital shadedrelief map of the lower 48 states (Thelin and Pike, 1991) succeeded the unique, if less accurate, hand-drawn landform map 

by master cartographer Erwin Raisz (1939).

The shaded-relief image of U.S. hills and dales is made 

up of some 12,000,000 minute squares—each one about 1/100 

of an inch (0.25 mm) on a side. The gray tone of each square 

is a brightness value computed from a mathematical relation that includes steepness of the local ground, the direction 

that its slope faces, and the positions of the observer and a 

simulated Sun. Light and dark tones show steeper areas; 

intermediate tones indicate gentler terrain. No actual shadows 

are included. The angle of surface slope and its sun-facing 

direction were computed from a digital elevation model, or 

DEM, a square-grid array of terrain heights spaced about 

1/2-mile (800 m) apart on the ground. These elevations were 

derived by semi-automated means from the height contours 

(at 50-, 100-, or 200-foot intervals) of older 1:250,000-scale 

USGS topographic maps. Further information about the 

shaded-relief technique, with details of the map’s construction, 

are given in Thelin and Pike (1991). Systematic descriptions 

of the terrain features shown on this tapestry, as well as the 

geology on which they developed, are available in Thornbury 

(1965), Hunt (1974), and other references on geomorphology, 

the science of surface processes and their resulting landscapes 

(Graf, 1987; Bloom, 1997; Easterbrook, 1998).

Landscape features contain many of the clues needed to 

understand the Earth and the agents that have shaped it (Pike, 

1991). Finding and decoding these clues enables scientists to 

learn more about natural hazards, the events of Earth history, 

and resources of land, water, energy, and minerals. Many 

methods of landscape portrayal are used to view surface features, but shaded-relief imaging by computer is unique in the 

following respects:

• It provides fine-scale detail over a wide area, a combination 

not possible in other techniques of illustration;

• It shows terrain accurately and in its true complexity, two 

properties commonly lost in sketches and diagrams of large 

areas;

• Unlike mosaics of aerial photos and radar images, the 

view—limited only by extent of the digital data set—is 

continuous across the country;

• Relief shading is free of distortion and the vegetation and 

cultural features that conceal topographic form on satellite 

images.

Geologic time

The second component of this tapestry, color, represents 

geologic time and is simplified from the geologic map of King 

and Beikman (1974a). Rocks contain information essential to 

an intelligent understanding of the Earth and its long natural 

history. Geologists determine the location, geographic extent, 

age, and physical and chemical characteristics of rocks and 

unconsolidated (loose) materials. To express these attributes 

geologists have developed a unique method of portrayal, the 

geologic map, which has the following properties:

• It recognizes similarities and differences among materials 

that comprise the Earth’s crust and classifies them by type 

of rock or surficial deposit;

• It ascribes Earth materials to a specific environment or 

mode of origin—for example, volcano, river deposit, windblown dune, limestone reef, or alteration at depth by heat or 

pressure;

• It identifies rock formations of distinctive materials and ages 

that are the three-dimensional building blocks of the Earth’s 

crust; it further shows the relative position of one formation 

to another at the Earth’s surface;

• It arranges rock formations of different ages into a time 

sequence from which the geologic history of the planet can 

be deciphered.

The original 161 colors and line patterns used by King 

and Beikman (1974a,b) to portray the age, location, and extent 
4

of materials that make up the lower 48 states are here reduced 

to 52 colors that show just the geologic ages of rocks and 

surficial deposits at the Earth’s surface. Combined colors and 

patterns were retained only for a few altered (metamorphic) 

rocks of uncertain age. Lines representing faults (for example, 

the San Andreas in California) were omitted. The map is a 

necessary compromise in that it emphasizes time intervals 

defined by bedrock rather than surficial materials. In areas affected by continental glaciation, for example, the ages shown 

are of underlying rocks, not the veneer of glacial (surficial) 

deposits. 

Geologists subdivide time variously by eras (Precambrian 

to Cenozoic), periods (Cambrian to Quaternary), and epochs—

only Pleistocene (early Quaternary) and Holocene (late Quaternary) are used here (see column on map). These units are 

quite uneven in elapsed time, the older intervals generally being 

of much longer duration. Rocks in the U.S. range in age from 

early Precambrian (2.6 billion years ago) to Holocene, which 

includes the present. The orderly sequence of Earth materials, 

from oldest to youngest, is represented by an equally wellordered sequence of “prismatic” colors (based on the rainbow). 

To improve the color balance of the tapestry, the Holocene is 

represented by two hues, light gray in the East and beige in the 

West. 

The King and Beikman geologic map of the U.S. was 

compiled from many detailed maps that describe the rocks of 

smaller areas. The constituent maps were made by many individuals from field and laboratory observations. These geologic maps distinguish among types of rocks that form in different 

ways: igneous granite and basalt; sedimentary sandstone, 

shale, and limestone; and metamorphic slate, marble, gneiss, 

and schist. From several converging lines of evidence—fossils, the layered sequence of strata, and the systematic radioactive decay of certain minerals—geologists have been able 

to place the rock formations in their correct time order, and 

from that arrangement construct a sequence of likely geologic 

events. Further information about the U.S. geologic map, including details of its compilation and descriptions of the major 

rock formations that occupy the time intervals shown here, are 

given in the four related reports by King (1976) and King and 

Beikman (1974b, 1976, 1978).

What this tapestry shows

The face of the United States has not always appeared as it does today. The land has been a shifting geologic 

battleground for well over two billion years, and the tapestry 

presented here records traces of many of the contributing skirmishes. Constructional forces, fueled by heat from the Earth’s 

interior, have built and rebuilt the North American continent 

from roving pieces of the planet’s exterior shell, only to give 

way before the processes of erosion, led by gravity and atmospheric moisture. Mountains raised episodically by tectonic

(crustal stress and strain) and magmatic (melting at depth) 

activity are reduced to sediment and dispersed into the oceans 

by the ceaseless work of rainfall and rivers. The surface 

on which we live today is only one snapshot in time of the 

constantly shifting balance, or dynamic equilibrium, between 

opposing geologic agents of construction and decay.

The geologic story of the U.S. told by the new map 

begins with tectonic plates, large segments of the Earth’s outer 

rigid layers that move about, or “drift”, on the plastic material 

beneath. The thinner oceanic plates are composed largely of 

denser (basaltic) rock; the thicker continental plates are rich 

in lighter (granitic) rocks. All the continental U.S. except its 

far west coast lies within the North American Plate. Continuous creation and recycling of plates—through the spreading of 

fresh sea-floor formed at oceanic ridges, subduction (descent 

and consequent melting) of one plate beneath another, and 

other broad-scale processes of plate tectonics—builds the 

planet’s largest features, its continents, and then redistributes 

and eventually reduces or destroys them. At least twice, all 

of Earth’s continental plates are believed to have collided and 

remained connected, forming a single landmass. The older 

of these proposed supercontinents, Rodinia (1.3 billion years 

ago), was followed much later by Pangaea (200-300 million 

years ago). Rocks and geologic structures in the lower 48 

states still bear traces of both events. Ice-cap glaciation during 

the Pleistocene Epoch (about 1.8 million to 10,000 years ago), 

which created much of the topographic detail in the tapestry, is 

the most recent major chapter in the story.

These and many other contending processes and events 

have given rise to the myriad of physical features portrayed 

in the new digital map. Forty-eight examples are described 

below in brief sketches, emphasizing phenomena—large and 

small—that owe their prominence on the tapestry to a combination of topographic texture and the color patterns defined by 

units of geologic time. The features are discussed in roughly 

chronological order, starting with the oldest, but no continuous narrative is intended. The discussion is intentionally 

non-technical. Detailed information on these and the many 

other features is available in the books and articles and their 

bibliographies listed in the appendix. We invite viewers of 

the new map to let their curiosity lead them where it may and 

to pursue whatever geologic and topographic questions strike 

their fancy. 

An interpretative tool that can help make sense out of 

the large amount of information contained in the new map is 

the regional classification shown on figure 1. Geomorphic, 

or physiographic, regions are broad-scale subdivisions based 

on terrain texture, rock type, and geologic structure and history. Nevin Fenneman’s (1928) three-tiered classification of 

the United States—by division, province, and section—has 

provided an enduring spatial organization for the great variety 

of physical features (see Graf, 1987, and other publications on 

geomorphology listed in the references). The composite image presented here clearly shows the topographic textures and 

generalized geology (by age) from which the physical regions 

were synthesized. The highlighted features represent many of 

these subdivisions. A second small map (figure 2) shows state 

boundaries and the numbered locations of specific features 

discussed below to further assist interpretation of the tapestry.

General features

The two major tectonic regimes of the U.S. contrast 

vividly in surface roughness, structural and coastline patterns, 
5

and freshness of relief: the active plate-margin of the West 

(exemplified by California’s San Andreas Fault Zone) and 

the static mid-plate East and Southeast (the eastern edge of 

the North American Plate lies at the Mid-Atlantic Ridge, not 

the east coast of the U.S.). The geologic youth of the West 

is evident in its many high mountains, fragmented terrain 

textures, and steep coast and continental shelf—indicated by 

absence of long, thin barrier islands just offshore. Geologic 

age reveals another broad-scale contrast. The eastern portion of the United States is dominated by continuous tracts 

of Paleozoic and Precambrian rocks. In the West, such older 

rocks appear only in isolated patches—exhumed by erosion, 

as in the ancient metamorphic rocks of the Grand Canyon’s 

Inner Gorge, or uplifted and exposed in the cores of ranges 

in the Rocky Mountains, for example, the billion-year-old 

Pike’s Peak Granite. The many types of mountains shown on 

the tapestry are complex features that form in different ways. 

Somewhat counterintuitively, they can arise from broad-scale 

forces either pushing on the crust (compression) or, oppositely, 

pulling it apart (extension). The architecture of the California Coast Ranges and the tightly folded Appalachians, for 

example, reflects compressional forces (although implemented 

in different ways and at different times), whereas that of the 

faulted mountain blocks in Utah and Nevada reveals an extensional origin.

Specific features

[Bracketed numbers in bold type locate features on the 

state index map, figure 2]

[1] The Superior Upland of Wisconsin and 

Minnesota is the largest U.S. surface exposure of the 

ancient (2.6 to 1.6 billion years old) core of the North 

American continent, known geologically as the Canadian Shield. (Even older rocks have been recognized 

in northwest Canada.) Now an area of low topographic 

relief, these metamorphic rocks once themselves 

formed mountains—located at the margin of a continent, as once were their later Appalachian and Rocky 

Mountain counterparts. Some of these highly altered 

rocks have been important sources of iron, copper, and 

other industrial metals.

[2] The Llano Uplift is conspicuous as a red 

and tan blotch in central Texas. A structural high, 

it provides a window into the underlying uplifted 

Precambrian rocks that formed a margin of the ancient 

supercontinent of Rodinia. These 1.0-1.3 billionyear-old metamorphic rocks belong to a long, now 

poorly exposed, mountain belt that once included 

what are parts of Scandinavia and Antarctica today. 

Similar rocks also appear in New York’s Adirondack 

Mountains.

[3] The Adirondack Mountains form most of 

northern New York state. They are an uplifted complex of Precambrian metamorphic rocks—like the 

Llano Uplift in Texas, a part of an ancient (Grenville) 

continental province. The Paleozoic sedimentary strata 

that now flank these older rocks once covered them. 

The intersecting faults and joints responsible for the 

rectilinear surface texture of the Precambrian rocks 

developed from release of pressure on this once deeply 

buried metamorphic complex.

[4] Another window into an ancient continent, 

the Baraboo Range in southern Wisconsin, appears as 

a small east-west-trending patch of tan about 25 miles 

(40 km) long. The resistant Precambrian quartzite that 

gives the Baraboos their topographic prominence today 

formed an erosional remnant, or monadnock (named 

for an isolated mountain in New Hampshire), as long 

ago as the late Precambrian. These ancestral mountains 

were buried by Paleozoic sedimentary strata and are 

still being exhumed by erosion of the softer overlying 

rocks.

[5] The winding course of the Colorado River 

through northern Arizona’s mile-deep Grand Canyon 

is well marked on the new map by a vivid contrast in 

pattern and color. A narrow ribbon of red differentiates 

the ancient granites and tilted metamorphic rocks along 

the river banks from the younger, overlying horizontal 

Paleozoic sedimentary rocks in the canyon walls and at 

the rim (blue). Abundant water from melting Pleistocene glaciers probably is responsible for the most 

recent episode of erosion that has deepened the canyon.

[6] Across the continent, alternating beds of hard 

and soft Paleozoic sedimentary rocks, folded like the 

wrinkles in a kicked floor rug, are the hallmark of the 

Appalachian Valley and Ridge Province. Extending 

some 900 miles (1500 km) from New York to Alabama, 

and flanked by flat-lying sedimentary strata to the west 

and Precambrian metamorphic rocks to the east, this 

famous belt of parallel structures reflects the several 

great continental collisions that formed the Appalachian chain and the Pangaea supercontinent some 300 

to 400 million years ago.

[7] Sequences of folded Paleozoic rocks in the 

southern Appalachians of Alabama and Tennessee 

match those in the eastern Ouachita Mountains of Arkansas, across the deep Mississippi River Embayment. 

Because these crustal wrinkles date to the same period 

of continental-scale collision, the two ranges once were 

almost certainly continuous. The gap, a 160-millionyear-old structural trough, is a legacy from the time 

when the collided masses of North and South America 

parted company and opened the Gulf of Mexico.

[8] Complex north-south patterns in the six New 

England states mirror a convoluted geologic story. 

This northern part of the Appalachians consists of 

several terranes, fault-bounded slices of the crust that 

have a tectonic history distinct from adjacent rocks. 

The terranes, which include rocks similar to those in 

the British Isles, originated elsewhere but were joined 

(accreted) to eastern North America in the Paleozoic 

during the formation of Pangaea. A Paleozoic fault 

zone comparable to the San Andreas, intrusion of 

Mesozoic igneous-rock masses, and later opening of 
6

the Atlantic Ocean have further complicated this New 

England portrait.

[9] A giant incomplete bulls-eye is centered on 

the state of Michigan. Extending into Illinois, Ohio, 

Indiana, Wisconsin, and Ontario, this annular pattern 

outlines the Michigan Basin, a bowl-shaped structure 

of uncertain origin that contains over 4 km of inwarddipping Paleozoic strata and a veneer of Jurassic 

sedimentary rocks. This mysterious basin is located 

in the tectonically less active interior of the continent, 

between the Appalachians and the Rocky Mountains. 

It subsided rapidly from Cambrian to Silurian time as 

it filled with shallow-water marine sediments, some of 

which host deposits of petroleum, coal, and salt.

[10] Nature is said to abhor a straight line, and 

geology is no exception. Why, then, the several northsouth linear contacts between different Late Cretaceous 

ages in North Dakota, Minnesota, and Iowa? The reasons are complex and reflect vagaries of the geologicmapping process rather than the geology itself: in this 

case, the bedrock formations defining time periods are 

so thin and discontinuous (and also overlain by glacial 

deposits), that their true contacts have yet to be located 

and thus were drawn arbitrarily—along nearby state, 

county, or even map-sheet boundaries, which often are 

straight lines.

[11] Other Mesozoic-age features are less ambiguous. The (green) hook-shaped N-S ridge just north 

of New York’s Long Island is a cuesta or hog-back

ridge, one of several tilted and eroded lava flows in 

the Connecticut Valley. It is contained within coarse 

Triassic-Jurassic sediments that were deposited rapidly 

during rift-faulting of North America, about 180-200 

million years ago, as the supercontinent of Pangaea 

was pulled apart and Europe and Africa separated from 

North America. When you are visiting Normandy in 

western France, look for the matching rocks!

[12] Florida is one of the many add-on appendages to eastern North America. Evidence of its overseas origin lies hidden beneath a cover of Tertiary and 

Quaternary sediments. The underlying rocks, unrepresented on this map but known from cores brought to 

the surface from drill holes, are an upper-Precambrian 

to lower-Paleozoic piece of western Africa that was 

added to the continent during formation of Pangaea 

and left behind in early Mesozoic time, when Pangaea 

broke up and created the Atlantic Ocean.

[13] The wide Coastal Plain belt of Late Cretaceous to Holocene deposits, extending from New 

Jersey to Texas, is one of the tapestry’s outstanding 

patterns. These sedimentary rocks, deposited mostly in 

a marine environment, were later uplifted and now tilt 

seaward; part of them form the broad, submerged Atlantic Continental Shelf. Coastal Plain deposits overlap 

the older, more distorted, Paleozoic and Precambrian 

rocks immediately to the north and west.

[14] The Fall Line is a low east-facing cliff paralleling the Atlantic coastline from New Jersey to the 

Carolinas. It separates hard Paleozoic metamorphic 

rocks of the Appalachian Piedmont to the west from the 

softer, gently dipping Mesozoic and Tertiary sedimentary rocks of the Coastal Plain. This erosional scarp, 

the site of many waterfalls, hosted flume- and waterwheel-powered industries in colonial times and thus 

helped determine the location of such major cities as 

Philadelphia, Baltimore, Washington, and Richmond.

[15] The Late Cretaceous and Early Tertiary 

periods were geologically more eventful in the West. 

The Rocky Mountains, which were uplifted about 50 to 

100 million years ago, extend from southern Colorado 

northwest to the Canadian border. Their rocks and 

topography are diverse and highly complex. Many of 

the individual ranges that make up the Rocky Mountains appear on the map as variously shaped bull’s-eyes 

surrounding a red-hued center. Each crudely ringed 

pattern was created by the Tertiary erosion of Paleozoic 

and Mesozoic sedimentary rocks that once overlay and 

now surround a core of uplifted Precambrian granite.

[16] Rising topographically from the Great Plains 

in eastern Wyoming and western South Dakota, the 

Black Hills are conspicuous on the map by the (red) 

outcrop of Precambrian granite. The upturned and 

eroded Paleozoic and Mesozoic strata of this structural 

dome surround the ancient granite on which the four 

faces of the Mt. Rushmore presidential monument were 

carved. Geologically, the Black Hills represent the 

easternmost outpost of the Rocky Mountains. 

[17] The Great Plains Province, a broad yellowish 

band down the center of the map, is a vast east-tilted 

surface formed by deposition of sediment eroded from 

the uplifting Rocky Mountains in Early Tertiary time, 

beginning about 65 million years ago. This upraised 

region now is being eroded, especially on its eastern 

margin, by many east-flowing rivers that expose the 

older rocks beneath. To the west, these older, largely 

Cretaceous, sedimentary rocks contain some of the Nation’s most spectacular dinosaur fossils.

[18] A north-northwest-trending terrain texture, 

or grain, evident as aligned ridges and valleys carved 

by segments of streams, pervades the northern and 

central Great Plains. This widely distributed pattern 

disappears north and east of the Pleistocene glacial 

margin. Both regional tectonism (fine-scale fracturing in the Earth’s crust induced by opposing horizontal 

forces) and surface processes (late-glacial wind action) 

have been suggested for the origin of this widespread 

texture.

[19] The Llano Estacado (“Staked Plains”) of 

west Texas and eastern New Mexico marks the southernmost extent of the High Plains. One of the largest 

expanses of near-featureless terrain in the U.S., it is an 

uplifted surface of porous, uneroded Late Tertiary river 

sediments veneered by late Pleistocene and Holocene 

wind-blown sand. The region was named by early 
7

European settlers who placed marker stakes to avoid 

losing their way on the flat land. (The faint, evenlyspaced wavy north-south lines on the map are a false 

artifact of the computer-processed terrain.)

[20] The Nation’s Far West is geologically 

younger and much more active than its East and Midcontinent. The northwest-southeast-trending OlympicWallowa Line across southern Washington state, for 

example, is a structural zone that includes active earthquake faults. This trend was first described from aerial 

photographs by Erwin Raisz (1939). Other northwesttrending alignments to the southeast, west of the central 

Rocky Mountains, perhaps are related geologically to 

this feature.

[21] The mountains in the Olympic Peninsula of 

northwest Washington State, which describe a backwards “C” on the map in yellow and light orange, also 

are quite young. This crescentic pattern took form in 

Tertiary time as the western margin of North America—much like its earlier Appalachian counterpart—

grew through the accretion of several geologic terranes, 

bits and pieces of drifting oceanic crust that collided 

with and became joined to the continent.

[22] Centered on the state of Nevada and extending from southern Oregon to western Texas, the Basin 

and Range Province is an immense region of alternating, north-south-trending, faulted mountains and flat 

valley floors. It has no counterpart elsewhere in the 

U.S. The province was created about 20 million years 

ago as the Earth’s crust stretched, thinned, and then 

broke into some 400 mountain blocks that partly rotated from their originally horizontal positions. These 

mountains of late Precambrian and Paleozoic rock 

continue to erode and fill the intervening valleys with 

fresh sediment.

[23] California’s Sierra Nevada (“snow-capped 

mountain”) is a west-tilting 350-mile (560-km)-long 

block of granite. Extending from 14,494 feet (Mt. 

Whitney, the highest peak in the lower 48 states) in 

the east to near sea level in the west, it contains the 

spectacular Yosemite and Sequoia National Parks (not 

indicated on the map). The massive granite intruded 

the crust in Mesozoic time and was uplifted and faulted 

in the Tertiary during formation of the Basin and Range 

province to the east. Eroded residue from the Sierra 

Nevada has filled the Central Valley of California, giving rise to both extensive agriculture and the 1849 Gold 

Rush.

[24] California’s Central Valley resembles a great 

elongate bath tub. Its present, remarkably flat surface 

consists largely of material eroded from the rising 

Sierra Nevada and Coast Ranges to the east and west, 

respectively, and deposited in low alluvial fans. On 

more than one occasion the valley impounded a large 

lake, which left behind a veneer of muddy deposits. 

About 650,000 years ago, rising waters of the most 

recent lake carved a gap through the mountain range to 

the west and drained into the Pacific Ocean through a 

low pass just south of the city of San Francisco.

[25] The topographic texture of western California is controlled by the San Andreas fault system, 

the tectonic expression of the Pacific Plate sliding 

northwestward along the western margin of the North 

American Plate. Hundreds of miles long and in places 

up to a mile wide, the San Andreas Fault Zone has been 

active since its origin in the Tertiary. About 10 percent 

of the present plate motion is compressional, shortening and wrinkling the crust to create the parallel coastal 

northwest-southeast mountain ranges. Comparatively 

quiet after the 1906 San Francisco earthquake until 

the 1989 Loma Prieta event, the fault is again showing 

activity.

[26] The intersection of the San Andreas and Garlock Faults in southern California reflects two different tectonic forces: northwest-southeast sliding along 

the Pacific and North American plate boundaries and 

roughly east-west crustal extension within the North 

American Plate. The relative westward movement of 

crust north of the Garlock Fault bends the San Andreas 

system into a lazy “S” pattern. This deflection results 

in a jamming of rocks to the south, expressed by the 

San Gabriel Mountains and other east-west-trending 

Transverse Ranges north of Los Angeles.

[27] Walker Lane is a linear north-northwesttrending depression extending some 500 miles (800 

km) north from the Garlock Fault-Las Vegas area to 

south-central Oregon. Within it are Walker, Goose, 

and Pyramid Lakes (shown on the tapestry). This 

trough is part of the Walker Lane Fault Zone, a major 

tectonic system that includes Owens and Death Valleys 

and several prominent faults. It is the site of current 

earthquakes. Located at the juncture of two contrasting 

tectonic styles, the Sierra Nevada and the Basin and 

Range, the Walker Lane region is deforming in a complex way by both extensional and transcurrent (sliding) 

fault movements.

[28] The Nation’s active tectonism is not confined 

to the Far West. In at least one place, the mid-section 

of the continent is beginning to be pulled apart by extensional forces. Volcanism accompanies this activity. 

The upper Rio Grande River flows southward through 

New Mexico within a long fault-bounded basin, the 

Rio Grande Rift, where lava from a source deep in 

the mantle periodically spreads across the surface. In 

the near geologic future, several million years or so, a 

youthful ocean basin may occupy this area.

[29-31] Thousands of volcanoes erupted throughout the western U.S. in the last 60 million years, 

but most individual craters are too small to show up 

clearly in the tapestry. Among the larger volcanoes, 

although still small at this scale, are two broad collapse cauldrons—Valles (a beige and yellow patch in 

the northwest Rio Grande Rift) [29] and Crater Lake 

(southwest Oregon) [30]. These two calderas formed in 
8

different ways. Mount St. Helens [31], which erupted 

catastrophically in 1980 (by yet a third mechanism), is 

smaller still and lies largely hidden among the many 

peaks in the Cascade Range of southwest Washington. 

[32] The great length and strong north-south linearity of the Cascade Range, a narrow yellow band extending from southern Washington to northern California, contrasts sharply with the varied directional trends 

of other mountain groups to the east and northeast. The 

Cascades arose through the plate collisions that have 

enlarged the western continent in Tertiary-to-Holocene 

time. This mountain range contains such large and 

geologically recent active volcanoes as Rainier, Hood, 

and Shasta.

[33] Interpreted by geologists as the southernmost 

volcano in the Cascade Chain, the now-inactive and 

highly dissected Sutter Buttes show up on the map as a 

small circular bump that contrasts sharply with its flat 

surroundings in California’s Central Valley. It erupted 

in Late Tertiary time—punching through flat-lying 

young sediments eroded from the rising Sierra Nevada 

to the east. 

[34-35] Low basalt shields [34] appear as even 

smaller bumps on the lava-flooded Snake River Plain, a 

kidney-shaped expanse in southern Idaho. The apparent decrease in age of these tiny Holocene volcanoes 

from west to east over the last 16 million years marks 

the movement of the North American Plate westward 

across a source of magma. Such hot spots or plumes

rise into the Earth’s crust from many miles deep in 

the underlying mantle. (A different one formed the 

Hawaiian Islands.) Yellowstone National Park [35] in 

northwest Wyoming currently lies above this particular 

source. The giant volcanic depression that contains the 

park and its geysers and hot springs (for example, Old 

Faithful) formed about 100,000 to 5 million years ago.

[36] Late Cenozoic ice-cap glaciation and its 

many geomorphic effects mark a chapter in U.S. Earth 

history that began some 2.0 million years ago and 

ended about 10,000 years ago. A subtle but widespread 

feature remarkable for its exposure on this composite 

image is the overall textural contrast created by the 

last of the several ice-sheet advances from Canada. 

Particularly in the mid-continent, topography north of 

the highly irregular line [36] marking the glacial limit 

is muted and smooth and lacks the strong river-carved 

grain characteristic of unglaciated terrain to the south.

[37] Isolated patches of rough terrain in the 

unglaciated Driftless Area of southwestern Wisconsin 

and northwestern Iowa stand out from the surrounding, smoothed glaciated ground. Thoroughly dissected 

by tributaries of the Mississippi River, the topography 

within these “islands” was engulfed but never overridden by the ice. The appearance of the Driftless Area 

landscape today probably is much like that of adjacent 

glaciated landscapes prior to the first Pleistocene ice 

advance.

[38] The north-pointing, flatiron-shaped Coteau 

des Prairies in eastern South Dakota is arguably the 

most conspicuous landform of the U.S. Midcontinent 

shown on this map. Some 200 miles (320 km) long, 

the low plateau of thick glacial deposits is underlain 

by a small ridge of resistant Cretaceous shale. Moving 

south along pre-glacial stream valleys just to the west 

and east, respectively, the James River and Des Moines 

Lobes of the last Pleistocene ice sheet probably parted 

at the stream divide preexisting the present Coteau 

(“hill” in French) and further deepened its flanking 

lowlands—which then drained meltwater as the glaciers retreated to the north.

[39] The low, arc-shaped ridges just west of the 

“thumb” region of northeast Michigan are recessional 

moraines composed of glacial rubble that overlie the 

Pennsylvanian-age bedrock shown on the map. They 

mark the northeastward retreat of the Huron Lobe of 

the last Pleistocene ice sheet from Saginaw Bay about 

10,000 years ago (Lake Huron is not shown). Similar moraines south of Lake Michigan, west of Lake 

Ontario, and in eastern Wisconsin (Green Bay) are not 

well represented by the rather coarse terrain data available to make the shaded relief map.

[40] Festoons of terminal moraines marking the 

southern limit of Pleistocene glaciation were deposited 

on a submarine ridge of Tertiary rocks off the coasts of 

Massachusetts and Connecticut 15,000 to 20,000 years 

ago. These hummocky piles of clay-rich, poorly-sorted 

glacial material, and the smoother plains of sandy outwash deposits immediately south of them, form much 

of Long Island, Cape Cod, Martha’s Vineyard, and 

Nantucket Island. They also controlled the post-glacial 

development of beaches, offshore islands, and other 

Holocene coastal landforms.

[41] Traces of an old east-west drainage system, 

buried by glacial deposits not shown on the map, are 

conspicuous across northern Ohio and Indiana. Presence of the pre-Pleistocene Teays River is revealed as a 

sinuous, branching pattern of Ordovician rocks (pink) 

surrounded by overlying Silurian strata (violet). The 

old river channel was abandoned when its course was 

diverted southward to the Ohio River drainage by the 

movements of early Pleistocene ice and the emplacement of glacial deposits, probably about 2 million years 

ago.

[42] The seven large Finger Lakes in central New 

York state were formed when the last Pleistocene ice 

cap melted back and flooded valleys previously overdeepened by scouring of the advancing glacial ice. A 

thick veneer of glacial debris, not shown here, overlies 

the lower Paleozoic bedrock indicated on the map. The 

native American Iroquois believed that the fan-shaped 

array of lakes are marks from the hand of the Great 

Spirit.

[43] Trail Ridge, the largest of several long, low 

north-trending ridges in central Florida, is among the 
9

most distinctive landforms in this area of low topographic relief. The ridges are complexes of sand dunes 

formed during the Pleistocene, when the coastline was 

some 300 feet lower than it is today. The sandy sediments were eroded from rocks of the Appalachian highland to the north. Some of the ridges are mined for the 

industrial minerals rutile and ilmenite, sources of the 

titanium metal used in the spacecraft operated at Cape 

Canaveral on Florida’s east coast.

[44] The largest field of sand dunes in the Western 

Hemisphere is located southeast of the Black Hills 

region and occupies much of western Nebraska. The 

Sand Hills, developed on the northernmost occurrence 

of Late Tertiary High Plains deposits (light yellow), are 

evident on the map as a fine-scale hummocky texture. 

The dunes formed as recently as 10,000 years ago, during and after Pleistocene time. Under modest changes 

in climatic conditions, these dormant features could 

shed their vegetative cover and again become active.

[45] Events of the Pleistocene also left their mark 

on major U.S. rivers. A conspicuous band of alternating 

Pleistocene (pale yellow) and Holocene (gray) deposits 

characterizes the broad, flat alluvial plain of the Mississippi River Embayment, its tributaries to the west, 

and coastal Texas. The irregularly striped pattern owes 

its origin to extensive and accelerated deposition by 

streams during interglacial phases of the Pleistocene, 

followed by erosion of these materials by Holocene 

river systems, over the last 1-2 million years.

[46] Crowleys Ridge, evident on the map in eastern Arkansas as a long yellow-orange ribbon against 

a gray background, is an erosional remnant of 40- to 

50-million-year-old sedimentary rock in the upper 

Mississippi River Embayment. The ridge formed 

late in the Pleistocene as the river, gorged with glacial 

meltwater, continually shifted course and broadened 

its floodplain at the expense of Tertiary rock forming 

its banks. Crowleys Ridge is located near the site of 

the great 8+ magnitude New Madrid earthquakes of 

1811-1812.

[47] The giant bird’s foot delta, featuring a large 

middle toe, that terminates the lower Mississippi 

River in southern Louisiana marks the seaward growth 

of land into the Gulf of Mexico. The MississippiMissouri River system collects eroded debris from the 

entire central half of the U.S. Upon reaching the Gulf 

the river’s velocity slows, abruptly reducing its capacity to carry suspended mud and sand, and the sediment 

is deposited in vast alluvial fans not visible on the map. 

These submarine fans are major sources of petroleum, 

natural gas, and sulfur.

[48] A large lake located by the scouring of 

Pleistocene ice hosts a geographical curiosity. The 

Northwest Angle, a 150 square mile (390 square km) 

tract separated from the rest of Minnesota by the Lake 

of the Woods, is the northernmost point in the United 

States exclusive of Alaska. The peninsula is connected 

to Manitoba and can be reached overland only by going 

through Canada. It was acquired in the 1783 Treaty of 

Paris, through an earlier surveying error made while 

attempting to locate the source of the Mississippi and 

other rivers. Most of the land is uninhabited and held 

in trust by the Red Lake Indian Reservation. 

Technical details

Combining the existing images of terrain and geologic 

time posed challenges not encountered in previous digital 

compilations. The constituent maps differ dramatically in 

scale, type of color, and the spatial structure of their digitized 

information. The gray-scale (monochrome) shaded-relief 

map, at a uniform 1:3,500,000 scale, is arrayed in a raster

(regular rectangular-grid) structure (Thelin and Pike, 1991). 

The geologic map is in multi-color, has a non-uniform scale of 

1:2,500,000, and is vector structured (irregular lines and polygons). The geologic map had been transformed earlier from 

the original paper product to a computer database by digital 

scanning and vectorizing (Schruben and others, 1998). About 

35 large lakes (shown in black) were added to aid in feature 

recognition.

The two maps were combined by converting the geologic map from vector to raster structure and overlaying the 

resulting data file on the shaded-relief file. The non-uniform 

scale of the geologic map posed difficulties in fitting it to 

the uniform scale of the shaded-relief map. Extraneous data 

cells were removed digitally with a global selection tool, and 

various procedures were applied where needed to adjust and 

“clean up” the combined image. (In such areas as the Basin 

and Range Province, registration of the two maps still is not 

perfect.) Transparency (opacity), color levels, and contrast 

of the geologic map were adjusted to attain an aesthetic and 

visual balance between shaded relief and geologic time. This 

was a trial-and-error process because colors on the computer 

screen differed substantially from those plotted on paper. 

Several test plots were made in RGB (color addition mixing) 

mode, at 72 and 300 dpi (dots per inch). Final prints, at image size 56 by 40 inches and sheet size 58 by 42 inches, were 

rendered in CMYK (color-subtraction mixing) mode at 2400 

dpi. The data are registered to an Albers Equal-Area Conic 

projection (standard parallels at 29.5° N. and 45.5° N; central 

meridian at 96.0° W., and latitude of projection’s origin at 

23.0° N.). Scale of the tapestry is slightly over 1:3,500,000, or 

about 55 miles to the inch.

The composite map was created by Vigil on an Apple 

Computer PowerMacintosh G3 450-MHz machine running 

under the Mac OS 8.6 operating system, with one GB (billion 

bytes) of RAM (random access memory), a 9-GB internal hard 

disk, and a 47-GB external disk. The size of the first composite image-file was 1.3 GB; the file prepared for final printing 

was much smaller, requiring scarcely 700 MB (million bytes). 

The software applications by which the two constituent maps 

were combined are Adobe Illustrator (version 8.1) and Adobe 

Photoshop (version 5.5). The test prints were made on a 

Hewlett-Packard HP 3500CP drum plotter.
10

PHYSIOGRAPHIC REGIONS OF THE LOWER 48

UNITED STATES

after Fenneman (1928)

LAURENTIAN UPLAND

1. Superior Upland

ATLANTIC PLAIN

2. Continental Shelf (not on map)

3. Coastal Plain

 a. Embayed section

 b. Sea Island section

 c. Floridian section

 d. East Gulf Coastal Plain

 e. Mississippi Alluvial Plain

 f. West Gulf Coastal Plain

APPALACHIAN HIGHLANDS

4. Piedmont province

 a. Piedmont Upland

 b. Piedmont Lowlands

5. Blue Ridge province

 a. Northern section

 b. Southern section

6. Valley and Ridge province

 a. Tennessee section

 b. Middle section

 c. Hudson Valley

7. St. Lawrence Valley

 a. Champlain section

 b. Northern section (not on map)

8. Appalachian Plateaus province

 a. Mohawk section

 b. Catskill section

 c. Southern New York section

 d. Allegheny Mountain section

 e. Kanawha section

 f. Cumberland Plateau section

 g. Cumberland Mountain section

9. New England Province

 a. Seaboard Lowland section 

 b. New England Upland section

 c. White Mountain section

 d. Green Mountain section

 e. Taconic section

10. Adirondack province

INTERIOR PLAINS

11. Interior Low Plateaus

 a. Highland Rim section

 b. Lexington Plain

 c. Nashville Basin

12. Central Lowland

 a. Eastern Lake section

 b. Western Lake section

 c. Wisconsin Driftless section

 d. Till Plains

 e. Dissected Till Plains

 f. Osage Plains

13. Great Plains province

 a. Missouri Plateau, glaciated

 b. Missouri Plateau, unglaciated

 c. Black Hills

 d. High Plains

 e. Plains Border

 f. Colorado Piedmont

 g. Raton section

 h. Pecos Valley

 i. Edwards Plateau

 k. Central Texas section

INTERIOR HIGHLANDS

14. Ozark Plateaus

 a. Springfield-Salem plateaus

 b. Boston “Mountains”

15. Ouachita province

 a. Arkansas Valley

 b. Ouachita Mountains

ROCKY MOUNTAIN SYSTEM

16. Southern Rocky Mountains

17. Wyoming Basin

18. Middle Rocky Mountains

19. Northern Rocky Mountains

INTERMONTANE PLATEAUS

20. Columbia Plateau

 a. Walla Walla Plateau

 b. Blue Mountain section

 c. Payette section

 d. Snake River Plain

 e. Harney section

21. Colorado Plateaus

 a. High Plateaus of Utah

 b. Uinta Basin

 c. Canyon Lands

 d. Navajo section

 e. Grand Canyon section

 f. Datil section

22. Basin and Range province

 a. Great Basin

 b. Sonoran Desert

 c. Salton Trough

 d. Mexican Highland

 e. Sacramento section

PACIFIC MOUNTAIN SYSTEM

23. Cascade-Sierra Mountains

 a. Northern Cascade Mountains

 b. Middle Cascade Mountains

 c. Southern Cascade Mountains

 d. Sierra Nevada

24. Pacific Border province

 a. Puget Trough

 b. Olympic Mountains

 c. Oregon Coast Range

 d. Klamath Mountains

 e. California Trough

 f. California Coast Ranges

 g. Los Angeles Ranges

25. Lower California province

Acknowledgments: We thank USGS colleagues Andrei 

Sarna-Wojcicki and King Huber for comments that improved 

content and presentation, Eleanore Jewel for assistance with the 

digital cartography, and Jane Ciener for editing the pamphlet.
11

References

Bloom, A.L., 1997, Geomorphology, a systematic 

analysis of late Cenozoic landforms: Englewood Cliffs, 

N.J., Prentice Hall, 482 p.

Easterbrook, D.J., 1998, Surface processes and landforms: Englewood Cliffs, N.J., Prentice Hall, 560 p.

Fenneman, N.M., 1928, Physiographic divisions of 

the United States: Annals of the Association of American 

Geographers, v. 18, p. 261-353.

Graf, W.L., ed., 1987, Geomorphic systems of North 

America: Geological Society of America, Centennial 

Special Volume 2, 643 p.

Hunt, C.B., 1974, Natural regions of the United 

States and Canada: San Francisco, W.H. Freeman, 725 p.

King, P.B., 1976, Precambrian geology of the United 

States; an explanatory text to accompany the geologic 

map of the United States: U.S. Geological Survey Professional Paper 902, 85 p.

King, P.B., and Beikman, H.M., compilers, 1974a, 

Geologic map of the United States (exclusive of Alaska 

and Hawaii): Reston, Va., U.S. Geological Survey, three 

sheets, scale 1:2,500,000. 

King, P.B., and Beikman, H.M., 1974b, Explanatory 

text to accompany the geologic map of the United States: 

U.S. Geological Survey Professional Paper 901, 40 p.

King, P.B., and Beikman, H.M., 1976, The Paleozoic 

and Mesozoic rocks; a discussion to accompany the geologic map of the United States: U.S. Geological Survey 

Professional Paper 903, 76 p.

King, P.B., and Beikman, H.M., 1978, The Cenozoic 

rocks; a discussion to accompany the geologic map of the 

United States: U.S. Geological Survey Professional Paper 

904, 82 p.

Pike, R.J., 1991, Surface features of central North 

America; A synoptic view from computer graphics: GSA 

Today, v. 1, no. 11, p. 241, 251-253. 

Raisz, Erwin, 1931, The physiographic method of 

representing scenery on maps: Geographical Review, v. 

21, no. 2, p. 297-304.

Raisz, Erwin, 1939, Landforms of the United States, 

in Atwood, W.W., 1940, The physiographic provinces 

of North America: New York, Blaisdell, scale about 

1:4,500,000.

Schruben, P.G., Arndt, R.E., and Bawiec, W.J., 1998, 

Geology of the conterminous United States at 1:2,500,000 

scale—A digital representation of the 1974 P.B. King and 

H.M. Beikman map: U.S. Geological Survey Digital Data 

Series DDS-11, Release 2, one CD-ROM. (http://pubs.

usgs.gov/dds/dds11/)

Thelin, G.P., and Pike, R.J., 1991, Landforms of 

the conterminous United States; A digital shaded-relief 

portrayal: U.S. Geological Survey Miscellaneous Investigations Map I-2206, scale 1:3,500,000. (http://pubs.usgs.

gov/imap/i2206/)

Thornbury, W.D., 1965, Regional geomorphology of 

the United States: New York, John Wiley, 609 p.
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Figure 1. Physiographic divisions (heavy lines), provinces (numbers), and sections (letters)  of the lower 48 states (from Fenneman and Johnson, 1946).

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Figure 2. Boundaries of the lower 48 states and the numbered physical features cited in this pamphlet.

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