Paleontology and geologyIn the Quaternary, sediments eroding from the highlands accumulated in floodplains and deltas in the east, building up the coastal plain along the Gulf of Mexico. In the west, the interactions between the oceanic and continental plates continued to create volcanoes, which poured lava and ash over surface. Gorges and canyons in the southwest formed as rivers cut their way through the volcanic deposits. From time to time, these rocks blocked the flow of water, and large lakes formed in low-lying areas. Wave action on these lakes cut terraces in many hillsides. Waves and higher sea levels also formed terraces of marine deposits along the coast and on Islas Marias in the west. The climate became drier through this period, and the land was covered in forests and grasslands. Mammoths, mastodons, camels, horses, deer, pronghorn, peccaries, glyptodonts, shrub ox, and ground sloths roamed the region. There were also lizards, frogs, tortoises, rabbits, shrews, porcupines and other rodents, which were hunted by dire wolves, American lions, saber-tooth cats, and bears. The skies were filled with bats and many different birds, including parrots, owls, hawks, vultures, jays, turkeys, ducks and other aquatic birds. |
