Throughout the Cretaceous the Rockies
continued to grow taller while the shallow Mowry Sea covered the
length of the central continent. Over time this sea retreated to
the south into the area now called the Gulf of Mexico.
Although dinosaurs continued to flourish through the Cretaceous,
with species like the tyrannosaurus and triceratops proliferating,
the most famous Cretaceous event was the mass extinction that marks
its end. All large land animals were killed, and up to 70% of marine
life was also destroyed. The ammonites, shelled marine predators,
were driven to extinction along with the dinosaurs. The extinction
is believed to have resulted from a huge asteroid that hit the earth
in the vicinity of the Yucutan Peninsula. This crater, the Chixulub
crater has since been filled in with sediments.
Other major features that are linked to the Cretaceous due to the
timing of their formation or the age of their rocks include the
Coteau des Praires, the
the Sierra Nevada,
the Rocky Mountains,
the Great Plains,
and Walker Lane.