Nature shaped the land in this part of Texas in a number of interesting ways. Millions of years ago, this land lay at the bottom of the sea, studded by carol reefs and rocky atolls. Geological forces and dramatic shifts in the earth’s surface caused the water’s edge to recede to the south and east. What were once continental shelves and underwater landforms eroded into mesas like those south of Big Spring, lines of hills like the Callahan Divide south of Abilene, and rocky escarpments like the Cap Rock near Lubbock.