A map of the major geologic regions of Colorado.
A map of the major geologic regions of Colorado.
Eastern
Plains Rocky Mountains Colorado Plateau Roughly forty
percent of the state is plains with the remaining area equally divided between the plateau
and mountain zones. Geologically, the
eastern plains and the western plateau are classified as sedimentary zones. This means
that the predominate rock type is sedimentary. There are igneous and
metamorphic areas in these zones, but they are small in comparison to the large
sedimentary area. The Rocky Mountain
region is comprised of a complex assortment of igneous, metamorphic, and sedimentary rock
formations with all three groups fairly equal in proportion to one another. Drainage throughout
the state occurs through three separate systems, with all rivers originating in the
mountains. All drainage west of
the Continental Divide flows into the Colorado River and out to the Gulf of California. The major tributaries
to the Colorado are the Yampa, White, Gunnison, Dolores, and San Juan. The major rivers east
of the Continental Divide are the North and South Platte, Arkansas, and the Rio Grande. Drainage east of the
Continental Divide flows into the Gulf of Mexico by the South Platte and the Arkansas
rivers which are part of the Mississippi system. Water from the
eastern slope of the San Juan Mountains drains into the Gulf of Mexico by the Rio Grande. The river valleys in
the mountains and the western plateau regions are generally canyons, whereas in the
eastern plains the river valleys are shallow with less relief. George, Russel D., Geology and Natural Resources of Colorado, Boulder, CO, University of Colorado, 1927.
Guide to the Geology of Colorado, ed. Weiner, Robert J. and Haun, John D., Geological Society of America, 1960.
Pearl, Richard Maxwell. Exploring Rocks, Minerals, and Fossils in Colorado, Chicago, Sage Books, 1969.
