Colorado Plateau Region
The Colorado Plateau:
The Colorado Plateau is an elevated, mildly folded
and faulted physiographic province generally underlain by
The sculptured beauty and brilliant colors of the
Colorado Plateau's sedimentary rock layers
have captured the imaginations of countless geologists.
This is a vast region of plateaus, mesas, and deep
canyons whose walls expose rocks ranging in age
from billions to just a few hundred years old.
Ancient Precambrian rocks,
exposed only in the
deepest canyons, make up the basement of the
Colorado Plateau. Most are
formed deep within the Earth while
continental collision on a grand scale produced the
nucleus of the North American
continent well over a billion years ago.
injected millions of years later form
a marbled network through parts of the Colorado Plateau's
darker metamorphic basement.
These deeply-formed rocks were uplifted,
eroded, and exposed for eons. By 600 million
years ago North America had been beveled off
to a remarkably smooth surface. It is on this
crystalline rock surface that the younger, more
familiar layered rocks of the Colorado Plateau
Paleozoic Era, the Colorado
Plateau region was periodically inundated by
It was not until the upheavals that coincided
with the formation of the supercontinent
Pangea began about 250 million years ago that
deposits of marine sediment waned and
terrestrial deposits dominate. The
sedimentary deposits are striking. Great
accumulations of dune sand hardened to form
sweeping arcs in cross-bedded sandstone.
Eruptions from volcanic mountain ranges to the
west buried vast regions beneath ashy
debris. Short-lived rivers, lakes, and inland
seas left sedimentary records of their
Beginning about 20 million
years ago, during the
the Colorado Plateau region
was uplifted as much as 3
kilometers. Great tension
developed in the crust, probably
related to changing plate motions
far to the west. As the crust
Basin and Range Province
broke up into a
multitude of down-dropped
valleys and elongate mountains.
Yet for some reason not fully
understood, the neighboring
Colorado Plateau was able to
preserve its structural integrity
and remained a single tectonic block.
Eventually, the great block of Colorado Plateau
crust rose a kilometer higher than the Basin and Range.
Carving the Land:
As the land rose, the streams responded by cutting
ever deeper stream channels. The
most well-known of these streams, the Colorado River,
began to carve the Grand Canyon
less than 6 million years ago. The forces of erosion
have exposed the vivid kaleidoscope
of rock layers that make the Colorado Plateau
a mecca for rock lovers.
-- Excerpt from:
USGS/NPS Geology in the Parks Website, 2001