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GEOLOGY OF SANDERSON

Sanderson and Terrell County, with a plentiful supply of bare rim rocks, ledges and cliffs, tell a story of the ancient Permian Sea. The birth of modern geology occurred in England in 1793 when a canal digger named William Smith discovered that the placement of fossils were the key to the identity of different layers of rock. Different kinds of fossils are found in different layers of rock. Each strata of rock can then be determined to be unique and can be identified whereever it is found in whatever part of the world. Thus the Permian period is identified by certain fossils that are found in the rock strata. The Permian period was first identified in Russia and then in England and Germany. The Permian in the United States is found in Texas, Missouri, Kansas and Nebraska and in the Appalachian area.

All around in every direction, you will be seeing limestone hillsides. You're in the Permian Basin. If you had been there some two hundred thousand years ago, you would be standing at the bottom of a sea, the Permian Sea. The part of the Permian where Terrell County is set, is all limestone that was laid down over an eon as the skeletons of many varieties of sea creatures sank to the bottom, creating layer after layer of sea floor. The Permian in Texas is up to five thousand feet thick, producing much oil and gas that is the result of that warm sea so rich in marine life.

A part of Terrell County is made up of low, rounded hills, but most of the county is mesa area with canyons branching off in every direction forming both wide and narrow valleys. Sanderson was established in one of the wider valleys with many-layered hillsides rising in all directions. Ledges, cap rocks and cliffs were laid bare over the years by erosion.

The geology of Terrell County in its position in the continental United States determined that it would be superior range for sheep and goats. Its position subjects it to both the east wind from the Gulf of Mexico and the southwest sub-tropical jet stream from the Pacific. But its remoteness from both bodies of water offers undependable rainfall. The area is subject to vicious thunderstorms during the hot season, resulting in raging torrents of floodwater racing down the normally dry gullies. The general southerly tilt of the geologic structure of the Sanderson area creates a gradient of about a hundred feet per mile, thus causing the racing flood waters to erode deeper and deeper in the canyons and valleys.

Geologically speaking, Terrell County is at times in a no-man's land, being deep within the Chihuahua Desert. As the desert expands, drought persists over the area, further increasing the erosion and exposing more of the Permian Basin's ancient seabed. Many kinds of fossils are found in the rocks and ledges. They are the significant clues that identify this to be the Permian period. The highway cuts along the road offer a most ready view of fossils and an insight into the interior of the Earth. Get a geologist's pick-hammer and a magnifying glass and take a look. You'll enjoy it.

Bill Goldwire
May 18, 2004


Page updated: May 21, 2004

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