Prehistory to 1518

1. Geologic History
2. Early Peoples and Indian Civilizations

Geologic History

Prehistory is the era before humans learned how to write. To learn prehistory, we depend on information provided by geologists, archeologists and anthropologists. Geologists study the earth. Archeologists study artifacts that ancient peoples left behind. Anthropologists also study artifacts and early human societies. 

Geologists believe that the Earth is at least 4 � billion years old. A geological timetable made by geologists describes how and when land was formed. To simplify their work, geologists divide the study of time into 3 units: eons, eras and periods. Different rocks and minerals appeared during these times because of glaciers, erosion, volcanoes, earthquakes and other natural events. Large amounts of sedimentary rocks can be found in Texas, including sandstone and limestone.  A geologic map shows the layers of land that have developed in Texas throughout its history.

Scientists believe that life began on Earth about four billion years ago. About 400 million years ago, much of Texas was covered by a vast inland sea. Part of it remained covered for about 100 million years. The water was like a thick soup and, eventually, it teemed with life. Fossil remains of fish, reptiles and other animals and plants that lived during this time can be found in rock formations in many areas of Texas. 

About 300 million years ago, Texas was located close to the equator. But as time passed, the North American continent drifted to the north toward its present location. About the same time, pressure inside the Earth caused volcanic explosions that created the mountains in Western and Southern Texas. Also fascinating is the Caprock in West Texas where the prairie gives way to the High Plains.

Over millions of years, new pressures inside the earth moved Texas� surface upward. The water drained off and the sea receded to the south. As mountains rose, regions around them dropped and formed large basins that filled with water where marine life continued to flourish. Through the eons, aquifers developed and now lie under about 70 percent of Texas. They provide sources of water for irrigation and drinking water for much of Texas. There is concern that overuse may drain the Ogallala Aquifer, which lies under the Texas Panhandle and other states to the north. This aquifer is the major source of water in that part of the country.

Additional Resources

1. What is "Prehistory"?
2. According to Geologists, how old is the Earth, and when did life first appear?
3. What was the environment in Texas like 400 million years ago?
4. What has happened to the earth's landmasses since 300 million years ago?
5. What are aquifers and why are they important?
6. Name three dinosaurs that lived in Texas.