The vast thicknesses of more recent sediments in the Texas coastal plain are riddled with salt domes and petroleum deposits, just like Mexico to the south and the Deep South states to the east. Their weight pushed the crust downward along the Gulf of Mexico throughout the Cenozoic Era, tipping their landward edges up in gentle cuestas that march inland in ever-older succession.
At the same time Texas was undergoing mountain-building, including continental rifting with attendant volcanism (shown in pink), in its far west. Great sheets of sand and gravel (shown in brown) washed down over the northern plains from the rising Rockies, to be eroded by streams and reworked by winds as the climate grew colder and drier. And the most recent period has built the world-class barrier islands and lagoons along the Texas Gulf coast.
Each period of Texas's geologic history is displayed in large areasappropriate for this enormous state. The University of Texas library has an online summary of the geologic history of Texas as shown on this map.
The browser-size version of this map is 800x1050 pixels and weighs 470 KB. It includes a key to the map units. The screen-size and Texas-size versions are 1200x1600 pixels (380 KB) and 2400x3100 pixels (1.1 MB), respectively.
More Texas Resources on About.com:
About San Antonio
Texas Geography, State Symbols & Facts
Texas Saltwater Fishing
Texas Water Parks