Bedrock Geologic Map of Arizona
(c) 2006 Andrew Alden, licensed to About.com, Inc. Derived from King and Beikman's Geologic Map of the United States, 1974. (fair use policy)
Arizona is divided roughly equally between the Colorado Plateau in the north and the Basin and Range province in the south.
The Colorado Plateau displays great expanses of flat-lying bedrock dating from the late Paleozoic Era through the Late Cretaceous Epoch. (Specifically, dark blue is late Paleozoic, lighter blue is Permian, and the greens signify Triassic, Jurassic and Cretaceous—see the time scale.) A great gash in the western part of the plateau is where the Grand Canyon exposes deeper rocks from the Precambrian. Scientists are far from a settled theory of the Grand Canyon. The edge of the Colorado Plateau, marked by the ribbon of darkest blue running from northwest to southeast, is the Mogollon Rim.
The Basin and Range is a wide zone where plate-tectonic motions have stretched apart the crust as much as 50 percent in the last 15 million years or so. The uppermost, brittle rocks have cracked like breadcrust into long blocks that have foundered and tilted upon the softer crust beneath. These ranges shed sediment into the basins between them, marked in light gray. At the same time, magma burst up from below in widespread eruptions, leaving lavas marked in red and orange. The yellow areas are continental sedimentary rocks of the same age.
The dark gray areas are Proterozoic rocks, some 2 billion years old, that mark the eastern part of Mojavia, a large block of continental crust that was attached to North America and broken off during the breakup of the supercontinent Rodinia, about a billion years ago. Mojavia may have been part of Antarctica or part of Australia—those are the two leading theories, but there are other proposals as well. Arizona will provide rocks and problems for many generations of geologists to come.
The 1250x1450 pixel version of this map shows the age symbols for all the rocks plus the rivers and cities of Arizona.
To purchase a larger, more useful map of Arizona's rocks, see the Arizona Geological Survey's publications page.
Other Arizona resources from About.com:
About Phoenix
Arizona Geography, State Symbols & Facts
Arizona Maps
Arizona Campgrounds
Arizona Travel Resources
More Arizona Travel Resources
Arizona Archaeology
Back to Geologic Maps of the States
