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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. This layer is part of the Geologic Map of the ... Geological Survey (U.S.).
2005. Reed, John Calvin, Jr. 1930- and Bush, Charles A. This polygon shapefile contains polygon boundaries, tags and labels for major geologic units in Alaska, Hawaii, Puerto Rico and the U.S. Virgin Isl... Geological Survey (U.S.).
1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, and 2005. Geological Survey (U.S.). This polygon shapefile portrays the state boundaries of the United States, and the boundaries of Puerto Rico and the U.S. Virgin Islands. The map l... Geological Survey (U.S.).