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Introduction

As part of an effort to map terrestrial ecosystems (Sayre and others, 

2009), the U.S. Geological Survey (USGS) has generated land surface form 

classes to be used in creating maps depicting standardized, terrestrial ecosystem models for the conterminous United States, using an ecosystems classification developed by NatureServe (Comer and others, 2003). A biophysical 

stratification approach, developed for South America (Sayre and others, 2008) 

and now being implemented globally (Sayre and others, 2007), was used to 

model the ecosystem distributions. Since land surface forms strongly influence 

the differentiation and distribution of terrestrial ecosystems, they are one of the 

key input layers in this biophysical stratification.

After extensive investigation into various land surface form mapping 

methodologies, the decision was made to use the methodology developed by 

the Missouri Resource Assessment Partnership (MoRAP). MoRAP made 

modifications to Hammond's (1964a, 1964b) land surface form classification, 

which allowed the use of 30-meter source data and a 1-km2 window for 

analyzing the data cell and its surrounding cells (neighborhood analysis) (True, 

2002; True and others, 2000). While Hammond's methodology was based on 

three topographic variables, slope, local relief, and profile type, MoRAP's 

methodology uses only slope and local relief (True, 2002). Using the MoRAP 

method, slope is classified as gently sloping when more than 50 percent of the 

area in a 1-km2 neighborhood has slope less than 8 percent, otherwise the area 

is considered moderately sloping. Local relief, which is the difference between 

the maximum and minimum elevation in a neighborhood, is classified into five 

groups: 0–15 m, 16–30 m, 31–90 m, 91–150 m, and >150 m. The land surface 

form classes are derived by combining slope and local relief to create eight 

landform classes: flat plains (gently sloping and local relief ≤ 15 m), smooth 

plains (gently sloping and 15 m < local relief ≤ 30 m), irregular plains (gently 

sloping and 30 m < local relief ≤ 90 m), escarpments (gently sloping and local 

relief > 90 m), low hills (not gently sloping and local relief ≤ 30 m), hills (not 

gently sloping and 30 m < local relief ≤ 90 m), breaks/foothills (not gently 

sloping and 90 m < local relief ≤ 150 m), and low mountains (not gently 

sloping and local relief > 150 m). However, in the USGS application of the 

MoRAP methodology, an additional local relief group was used (> 400 m) to 

capture additional local topographic variation. As a result, low mountains were 

redefined as not gently sloping and 151 m < local relief < 400 m, and a new 

land surface form class, high mountains/deep canyons, was identified as not 

gently sloping and local relief > 400 m. The final application of the MoRAP 

methodology was implemented using the USGS 30-meter National Elevation 

Dataset (NED, http://seamless.usgs.gov/index.php) and an existing USGS 

slope dataset that had been derived by calculating the slope from the NED in 

Universal Transverse Mercator (UTM) coordinates in each UTM zone, and 

then combining all of the zones into a national dataset.

This map shows a smoothed image of the nine land surface form classes 

based on MoRAP's methodology. Additional information about this map 

and any data developed for the ecosystems modeling of the conterminous 

United States is available online at http://rmgsc.cr.usgs.gov/ecosystems/.

References Cited:

Comer, Patrick, Faber-Langendoen, Don, Evans, Rob, Gawler, Sue, Josse, 

Carmen, Kittel, Gwen, Menard, Shannon, Pyne, Milo, Reid, Marion, 

Schulz, Keith, Snow, Kristin, and Teague, Judy, 2003, Ecological systems 

of the United States—A working classification of U.S. terrestrial systems: 

NatureServe, Arlington, Va. Accessed July 21, 2009 at 

http://www.natureserve.org/library/usEcologicalsystems.pdf.

Hammond, E.H., 1964a, Analysis of properties in land form geography—An 

application to broad-scale land form mapping: Annals of the Association 

of American Geographers, v. 54, no. 1, p. 11–19.

Hammond, E.H., 1964b, Classes of land surface forms in the forty-eight 

states—U.S.A.: Annals of the Association of American Geographers, v. 

54, no. 1, map supplement no. 4, scale 1:5,000,000.

Sayre, Roger, Yanosky, Alberto, and Muchoney, Doug, 2007, Mapping global 

ecosystems—The GEOSS approach: Group on Earth Observations, ed.: 

London, U.K., Tudor Rose. 

Sayre, Roger, Bow, J., Josse, C., Sotomayor, L., and Touval, J., 2008, Terrestrial ecosystems of South America, Campbell, J.C., Jones, K.B., and 

Smith, J.H., eds., in North America Land Cover Summit—A Special Issue 

of the Association of American Geographers: Association of American 

Geographers, p. 131–152.

Sayre, Roger, Comer, Patrick, Warner, Harumi, and Cress, J.J., 2009, A new 

map of standardized terrestrial ecosystems of the conterminous United 

States: U.S. Geological Survey Professional Paper 1768, 17 p. Accessed 

July 21, 2009 at http://pubs.usgs.gov/pp/1768.

True, Diane, 2002, Landforms of the Lower Mid-West, Missouri Resource 

Assessment Partnership (MoRAP): Columbia, Mo., University of 

Missouri MoRAP Map Series MS–2003–001, scale 1:1,500,000. 

Accessed Oct. 2008 at 

http://www.cerc.usgs.gov/morap/Maps.aspx?MapID=7.

True, Diane, Gordon, T., and Diamond, D., 2000, How the size of a sliding 

window impacts the generation of landforms: Missouri Resource Assessment Partnership (MoRAP). Accessed Oct. 2008 at 

http://www.cerc.usgs.gov/morap/projects.aspx?project_id=17.

U.S. Geological Survey, 2004, The National Map—National Elevation Dataset 

(NED): U.S. Geological Survey. Accessed Jan. 2006 at 

http://seamless.usgs.gov/index.php.

Terrestrial Ecosystems—Land Surface Forms of the Conterminous United States

By Jill J. Cress, Roger Sayre, Patrick Comer,1 and Harumi Warner2

2009

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3085

Version 1.0

Suggested citation:

Cress, J.J., Sayre, Roger, Comer, Patrick, and Warner, Harumi, 2009, Terrestrial Ecosystems—Land 

Surface Forms of the Conterminous United States: U.S. Geological Survey Scientific Investigations 

Map 3085, scale 1:5,000,000, 1 sheet.

Publishing support provided by: 

Denver Publishing Service Center

Manuscript approved for publication on June 29, 2009

For more information concerning this publication, contact:

USGS Central Region Geospatial Information Office

Federal Center

Box 25286

Denver, CO 80225

1-888-ASK-USGS or

Jill Cress

Rocky Mountain Geographic Science Center

U.S. Geological Survey

(303) 202-4275

jjcress@usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and 

does not imply endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, 

it also contains copyrighted materials as noted in the text. 

Permission to reproduce copyrighted items for other than personal use must be 

secured from the copyright owner. 

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

1-888-ASK-USGS

This and other USGS products are available on the World Wide Web at:

http://store.usgs.gov/

This report is available at:

http://pubs.usgs.gov/sim/3085

1 Ecology Department, NatureServe, Boulder, Colo.

2 Parallel Inc., Lakewood, Colo.

Prepared in collaboration with NatureServe

SCALE 1:5 000 000

100

100

100

100

0

0 200

200 300

300 400

400 500 MILES

500 KILOMETERS

Map projection: Albers Equal Area Conic

NAD 83 DATUM

Flat plains

Smooth plains 

Irregular plains 

Escarpments

Low hills

Hills

Breaks/foothills

Low mountains

High mountains/deep canyons

State boundaries

EXPLANATION

Land Surface Form Classes