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Surficial Deposits and Materials in the Eastern and Central United States (East of 102 Degrees West Longitude)
What this map layer shows: Surficial deposits and other surface materials that accumulated or formed during the past 2+ million years, such as soils, alluvium, and glacial deposits.
Background Information
Sample Map Surficial materials, referred to collectively by many geologists as regolith, are the mantle of fragmented and generally unconsolidated material that overlies the bedrock foundation of a continent. Included are soils, deposits, and residual materials. In recent years, surficial deposits and materials have become the focus of interest by national, State, and other governmental agencies; by engineering and construction companies; by environmental professionals; academic scientists and institutions; and by the general public. Surficial materials are the foundations of ecosystems, the materials that support plant growth and animal habitat, and the materials through which travels much of the water required for our agriculture, our industry, and our general well being. They also are materials that easily can become contaminated by pesticides, fertilizers, and toxic wastes. Potential uses of the information in the map layer include studies to evaluate hazards such as earthquakes, landslides, swelling clay, floods, and volcanic eruptions; studies to locate commercial materials such as aggregate, peat, and clay; and studies to identify areas of intense erosion or areas of potential contamination of soil and groundwater. Surficial materials are distinguished in part on the basis of particle size or texture, particle lithology or composition, and other physical, chemical, and engineering characteristics. The surficial units in this map layer are soils that are recognized in engineering geology, or are substrata or parent materials in which agricultural soils are formed. The textural or particle size divisions (e.g., clay, sand, pebbles, boulders) and the matrix nomenclature (e.g., loamy sand, clay loam, silty clay) of the U.S. Department of Agriculture are used in the map layer to ensure uniformity of terminology. This map layer was compiled by the U.S. Geological Survey. The Surficial Deposits and Materials in the Eastern and Central United States (East of 102 Degrees West Longitude) map layer shows the surficial deposits and other surface materials that accumulated or formed during the past 2+ million years, such as soils, alluvium, and glacial deposits. Also included is a detailed glacial limit line showing the position of maximum glacial advance during various geologic time periods. Descriptive information includes the origin, age, and composition of the geologic units, as well as the time periods associated with the detailed glacial limits. Even more detailed descriptive information on the surficial materials and deposits, including the thickness of deposits or depth to underlying deposits or materials or to bedrock can be found in the online pamphlet Map of Surficial Deposits and Materials in the Eastern and Central United States (East of 102 Degrees West Longitude). Further information on general geology is available from the USGS Geology Discipline home page, and information on geologic mapping is available from the USGS Learning Web.
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