Texas Almanac, 1992-1993 Page: 65
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Pliocene, Miocene, I Permion
E Pennsylvanian and Mississipplan
Devonian, Silurion, Ordovician, o 00mi
Cretaceous and Cambrlan
(Gulf series) Pre-Cambrian (schist and gneiss)
(Comanche series) Igneous (undifferentiated)
Geology of Texas
This article on the geology of Texas was prepared by the Bureau of Economic Geology at The University of Texas
History in the Rocks
The fascinating geologic history of Texas is recorded
in rocks - both those exposed at the surface and those
penetrated by holes drilled in search of oil and natural
gas. The rocks reveal a dynamic, ever-changing earth -
ancient mountains, seas, volcanoes, earthquake belts,
rivers, hurricanes and winds. Today, the volcanoes and
great earthquake belts are no longer active, but rivers
and streams, wind and rain, and the slow, inexorable al-
terations of rocks at or near the surface continue to
change the face of Texas. The geologic history of Texas,
as documented by the rocks, began more than a billion
years ago; its legacy is the mineral wealth and varied
land forms of modern Texas.
Geologic Time Travel
The story preserved in the rocks requires an under-
standing of the origin of the strata and how they have
been deformed. Stratigraphy is the study of the composi-
tion, sequence and origin of the rocks: of what the rocks
are made, how they were formed and the order in which
the layers were formed. Structural geology reveals the
architecture of the rocks: the locations of the mountains,
volcanoes, sedimentary basins and earthquake belts.
The map above shows the rocks of various geologic ages
at the surface of Texas today.
History concerns events through time, but geologic
time is such a grandiose concept that most of us find it
difficult to comprehend. So, geologists have named the
various chapters of earth history.
Precambrian rocks, more than 600 million years old,
are exposed at the surface in the Llano Uplift of Central
Texas and in scattered outcrops in West Texas, around
and north of Van Horn and near El Paso. These rocks,
some more than a billion years old, include complexly
deformed rocks that were originally formed by cooling
from a liquid state as well as rocks that were altered
from pre-existing rocks.
Precambrian rocks, often called the "basement
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Reference the current page of this Book.
Kingston, Mike. Texas Almanac, 1992-1993, book, 1991; Dallas, Texas. (texashistory.unt.edu/ark:/67531/metapth279642/m1/69/: accessed April 30, 2017), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; crediting Texas State Historical Association.