Outlines of Major Calderas and Impact Structures: Generalized Geologic Map of the Conterminous United States, 2005
- King, Philip B., Arndt, Raymond E., Schruben, Paul G., Bawiec, Walter J., and Beikman, Helen M.
- This line shapefile shows the outlines of major calderas and impact structures in the United States. A caldera is a large, generally circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir. An impact structure is a crater formed by the impact of a meteoroid, asteroid, or comet with the Earth.This layer is part of a Generalized Geologic Map of the United States, originally published at a scale of 1:2,500,000 (King and Beikman, 1974b). It excludes Alaska and Hawaii. These data depict the geology of the bedrock that lies at or near the land surface, but not the distribution of surficial materials such as soils, alluvium, and glacial deposits. This is a revised version of the April 2004 data set. This map complements the Generalized Geologic Map of Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands by Reed and Bush. A geographic information system (GIS) allows combining and overlaying of layers for analysis of spatial relations not readily apparent in the standard paper publication. This layer is part of the 1997-2014 edition National Atlas of the United States.Conversion of the geologic map of the U.S. to a digital format was undertaken to facilitate the presentation and analysis of earth-science data. Digital maps can be displayed at any scale or projection, whereas a paper map has a fixed scale and projection. However, these data are not intended to be used at any scale finer than 1:2,500,000.
- Geological Survey (U.S.)
- Alabama, Arizona, Arkansas, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York (State), North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, Rocky Mountains, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington (D.C.), Washington (State), West Virginia, Wisconsin, Wyoming, and United States
- Calderas, Impact craters, and Geoscientific Information
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- This item is in the public domain. There are no restrictions on use.
- This work is in the Public Domain, meaning that it is not subject to copyright.
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