Texas Almanac, 1939-1940 Page: 27
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AN OUTLINE OF THE GEOLOGY, PHYSIOGRAPHY
AND GEOGRAPHY OF TEXAS.
It is proposed on the following pages
to give, in story, statistics, and in pic-
tures, maps and graphs the drama of
Texas and Texans from the time that the
first white men, Pineda and his compan-
ions, set foot on Texas soil in 1519, to the
present day. In so far as possible, the
logical historical sequence will be fol-
lowed, although, in some instances, me-
chanical difficulties of publishing will in-
tervene and, in other instances, the very
intricacy of the many-sided develop-
ment of Texas will make proper se-
quence a matter of judgment. At any
rate, the account will be started with a
description of the stage upon which the
drama has been performed.
A bird's-eye view of Texas reveals a
great circular, tilted plain, sloping like
an amphitheater north, northwest and
west, upward from the Gulf of Mexico.
While especial attention will be given to
that part of the amphitheater lying with-
in the political boundaries of Texas, some
consideration will be given to related
outside areas included in what is general-
ly known as the Gulf Southwest-Louisi-
ana, Arkansas, Oklahoma and New Mex-
ico in addition to Texas. In a measure,
the same consideration must be given in
many of the chapters to physiographic,
historic and commercial relationship
with Mexico, facing Texas along 900
miles of the Rio Grande.
Looking across the broad expanse of
the surface of Texas one observes four
great physiographic regions, each of
which extends from beyond the border of
Texas into this state, making it a cross-
roads of geologic and physiographic con-
ditions. These four great areas are (1)
the Coastal Plains, (2) the North Cen-
tral Region, (3) the Great Plains, and (4)
the Trans-Pecos Mountain Region. Each
of these is broken into physiographic
subdivisions. These four great physio-
graphic regions are the surface indica-
tions of great geologic formations be-
neath. From the rocks of these great for-
mations have come the soils that have
been the basis of Texas' economic and
cultural progress. Within these subter-
ranean strata are the reservoirs of oil
and gas and deposits of sulphur, coal and
lignite and other minerals that have,
next to the soils, contributed most to
Texas' wealth and progress.
These resources of the rocks and soils,
together with the resources of the cli-
mate, constitute the physical influences
that justify geographers in saying that
"in the physical characteristics of a coun-
try is found the destiny of its people."
Soils and climate produce the indigenous
and cultivated vegetation and the animal
life which constitute the basic industries
of mankind. Add to this the economic
influences arising from mineral deposits
and the availability, or lack of availa-
bility, of ports and navigable rivers, and,
in addition, the influences of mountain
barriers or deserts, and one can compre-
hend the meaning of the geographer's
As a matter of fact, the maxim might
be pursued further back into the earth's
history and deeper beneath the earth's
surface than the geographer's applica-
tion to current and surface characteris-
tics. In a measure, a country's destiny
comes from the rocks that crop out at
its surface, and from which its surface
soils have eroded.
The geology of Texas is varied and in-
teresting. It has been said by Dr. Rob-
ert T. Hill, often called the dean of
Texas geologists, that Texas is at the
crossroads of North American geology.
The map on page 32 shows the age of
rocks outcropping at the surface or im-
mediately underlying the soil of Texas.
The vertical cross section diagram on
page 33 gives a very general idea of the
subsurface position of these structures,
showing how they dip sharply toward
the southeast below the Balcones Escarp-
ment and have a very gentle downward
slope toward the northwest above this
line of demarcation.
At times in the past great seas have
covered practically the whole of present
Texas, and it has been these submer-
gences and emergences that have laid
down the great strata of sedimentary
rock that largely constitute the geology
Though most of the geologic forma-
tions are of sedimentary origin, there are
places where the igneous rises to the
surface, notably in the Burnet-Llano
area and in the Trans-Pecos. Igneous
rock is that which was at one time in
molten state. Igneous intrusions which
came from the depths to near the sur-
face and solidified form the beautiful
granites of Central and Trans-Pecos
Texas. Erosion has uncovered the tops
of these great buried columns of stone
in many places, as at Granite Mountain
in Burnet County, which produced the
beautiful stone of which the State Cap-
itol was built. At other points, notably
along the Balcones Escarpment below
Austin and in the Trans-Pecos, there are
evidences of volcanic activity where ages
ago molten masses of rock were cast out
on the surface.
The geologic activity of the ages has
an important bearing on the economic
life of Texas today, not only because of
the soils that have been produced by the
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Texas Almanac, 1939-1940, book, 1939; Dallas, Texas. (texashistory.unt.edu/ark:/67531/metapth117163/m1/29/: accessed February 20, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; crediting Texas State Historical Association.