Texas Almanac, 2004-2005 Page: 61
The following text was automatically extracted from the image on this page using optical character recognition software:
rainfall, exposing bottoms of solid salt, and for years they
were a source of commercial salt.
The Davis Mountains are principally in Jeff Davis
County. The highest peak, Mount Livermore, (8,378 feet)
is one of the highest in Texas; there are several others
more than 7,000 feet high. These mountains intercept the
moisture-bearing winds and receive more precipitation
than elsewhere in the Trans-Pecos, so they have more
vegetation than the other Trans-Pecos mountains. Note-
worthy are the San Solomon Springs at the northern
base of these mountains.
South of the Davis Mountains lies the Big Bend coun-
try, so called because it is encompassed on three sides by
a great southward swing of the Rio Grande. It is a moun-
tainous country of scant rainfall and sparse population. Its
principal mountains, the Chisos, rise to 7,825 feet in
Mount Emory. Along the Rio Grande are the Santa
Elena, Mariscal and Boquillas canyons with rim eleva-
tions of 3,500 to 3,775 feet. They are among the notewor-
thy canyons of the North American continent. Because of
its remarkable topography and plant and animal life, the
southern part of this region along the Rio Grande is home
to the Big Bend National Park, with headquarters in a
deep valley in the Chisos Mountains. It is a favorite recre-
Upper Rio Grande Valley
The Upper Rio Grande (El Paso) Valley is a narrow
strip of irrigated land running down the river from El Paso
for a distance of 75 miles or more. In this area are the his-
toric towns and missions of Ysleta, Socorro and San
Elizario, oldest in Texas. Cotton is the chief product of
the valley, much of it the long-staple variety. This limited
area has a dense urban and rural population, in marked
contrast to the territory surrounding it.
For Further Reading:
"Texas: A Geography," by Terry G. Jordan with John L.
Bean Jr and William M Holmes; Westview Press, Boulder and
Geology of Texas
Source: Bureau of Economic Geology The University of Texas at Austin: www.beg utexas edu/
History in the Rocks
Mountains, seas, coastal plains, rocky plateaus, high
plains, forests - all this physiographic variety in Texas is con-
trolled by the varied rocks and structures that underlie and crop
out across the state. The fascinating geologic history of Texas
is recorded in the rocks - both those exposed at the surface
and those penetrated by holes drilled in search of oil and natu-
ral gas. The rocks reveal a dynamic, ever-changing earth -
ancient mountains, seas, volcanoes, earthquake belts, rivers,
hurricanes and winds. Today, the volcanoes and great earth-
quake belts are no longer active, but rivers and streams, wind
and rain, and the slow, inexorable alterations 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 rocks requires an understanding of
the origin of strata and how they have been deformed. Stratig-
raphy is the study of the composition, sequence and origin of
rocks: what rocks are made of, how they were formed and the
order in which the layers were formed. Structural geology
reveals the architecture of rocks: the locations of the moun-
tains, volcanoes, sedimentary basins and earthquake belts.
The map on the following page shows where rocks of various
geologic ages are visible on the surface of Texas today. History
concerns events through time, but geologic time is such a gran-
diose concept, most find it difficult to comprehend. So, geolo-
gists 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 origi-
nally formed by cooling from a liquid state as well as rocks that
were altered from pre-existing rocks.
Precambrian rocks, often called the "basement complex,"
are thought to form the foundation of continental masses. They
underlie all of Texas. The outcrop in Central Texas is only the
exposed part of the Texas Craton, which is primarily buried by
younger rocks. (A craton is a stable, almost immovable portion
of the earth's crust that forms the nuclear mass of a continent.)
During the early part of the Paleozoic Era (approximately
600 million to 350 million years ago), broad, relatively shallow
seas repeatedly inundated the Texas Craton and much of
Rock climbing is a favorite activity at Lake Mineral Wells State
Park in Parker County The area has outcroppings of Creta-
ceous, Pennsylvanian and Mississippian rock. File photo.
North and West Texas. The evidence for these events is found
exposed around the Llano Uplift and in far West Texas near Van
Horn and El Paso, and also in the subsurface throughout most
of West and North Texas. The evidence includes early Paleo-
zoic rocks - sandstones, shales and limestones, similar to
sediments that form in seas today - and the fossils of animals,
similar to modern crustaceans - the brachiopods, clams,
snails and related organisms that live in modern marine envi-
Here’s what’s next.
This book can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Book.
Alvarez, Elizabeth Cruce. Texas Almanac, 2004-2005, book, 2004; Dallas, Texas. (texashistory.unt.edu/ark:/67531/metapth162511/m1/61/: accessed October 18, 2017), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; crediting Texas State Historical Association.