Paleontology and geology
Throughout the Cretaceous, shallow seas continued to flood much of the Southeastern Region of Mexico. Highlands in the south remained above sea level and were covered in forests, swamps, and wetlands inhabited by turtles, crocodiles, and dinosaurs, among other animals. Along the coasts, deposits of salt, gypsum, and anhydrite accumulated in lagoons when sea water evaporated, while in deeper areas, rudist bivalves built up reefs. The shallow to deep seas were also home to corals, sponges, crabs, gastropods, echinoderms, bony fish, sharks, ichthyosaurs, and pliosaurs. Subduction added the last volcanic islands, slices of oceanic crust, and marine sediments in the southwest. This activity created volcanoes, formed masses of granite below the surface, and folded, faulted, and altered many rocks in the region. At the end of the period, a large meteor crashed into the northern part of the Yucatan Peninsula. The impact generated a giant tsunami, sent tons of dust and debris into the atmosphere, and left a crater over 150 miles wide. It also may have contributed to the mass extinction at the end of the Cretaceous.