First Tennesseans

Tennessee Was Once a Sea!

Tennessee was not always a land environment. About four billion years ago the area which is now Tennessee was completely covered with water. The inhabitants of our state during this time were creatures like algae and jellyfish. 

Several billion years later, land began to emerge from the water as a result of mountain building.   Limestone and sediments from volcanic activity were deposited across the area. Different plants and animals began to appear. These included trilobites, corals, sponges, and crinoids. [The longest trilobite fossil found in Tennessee was 12 inches long and found in Hardin County.]

About 300 million years ago, as underwater volcanoes continued, lagoons, barrier islands, tidal pools, swamps, and beaches began to emerge from the water. Land plants become more prevalent and trees and ferns begin to accumulate. 

The last major mountain-building that affected Tennessee happened about 250 million years ago. The movement of the Earth’s plates caused a collision with Africa and the North American-European continents. This collision caused the formation of several of the valleys and ridges of Tennessee. 

During this period the largest mass extinction on Earth took place. At this time there were many types of reptiles and amphibians on land along with many plants. There were also many sea animals. Something happened that caused the mass deaths of land and sea organisms.

From looking at fossil records, scientists estimate that nearly 90 percent of all life forms on Earth died in this extinction. No one knows what caused the mass extinction. It took nearly 50 million years for life on land to recover.. Dinosaurs emerged and lived in the area.

The sea moved back into West Tennessee from the south and formed what is now the Mississippi River. 


   First Tennesseans >>  Learning About the Past >>  Before the 1st Tennesseans >>  Tennessee Was Once a Sea!

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