Eleanore Jewel, David Howell, Naomi Kalman, United States Geological Survey, United States Geological Survey, United States Geological Survey, United States Geological Survey
Explore the new, interactive, digital map created from merging two United States Geological Survey (USGS) maps that depict the topography and geology of the United States. This composite is the most detailed and accurate portrait of the U.S. land surface and the ages of its underlying rock formations. 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. By 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. Creation information is given for each component map. The geologic map is an adaptation of the 'Geologic Map' of King and Beikman (1974), while the topography half is derived from the 'Digital Shaded-Relief Image', created by Thelin and Pike (1991). Over forty unique features are explained, with links to information about the respective geologic time periods of which they are a part. A legend page displays a clickable geologic time scale, which when a period is selected all features that correspond to the chosen time frame are highlighted and hypertext directs to specific discussions. A page for 'Boundaries' divides the continental U.S. by state borders and physiographic regions. The state borders map allows display of each individual state with the corresponding geologic legend of depicted features, whereas the physiographic regions map lists the broad-scale subdivisions which are based on terrain texture, rock type, and geologic structure and history. An online puzzle allows resource users to test their knowledge of the locations of the small-scale physiographic divisions. Finally, a 'Panorama Movie' of the maps is presented.
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