Cretaceous Period

Cretaceous Period

The Cretaceous Period is a geologic period and system that spans 79 million years from the end of the Jurassic Period about 145 million years ago (Mya) to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, which is often called the "Age of Reptiles" or "Age of Dinosaurs". The Cretaceous is notable for being the longest period of the Phanerozoic Eon.

Etymology

The name "Cretaceous" is derived from the Latin word "creta", meaning "chalk", which refers to the extensive chalk deposits of this age found in Western Europe.

Geology

The Cretaceous Period is divided into two epochs: the Early Cretaceous and the Late Cretaceous. The Early Cretaceous spans from 145 to 100.5 Mya, while the Late Cretaceous spans from 100.5 to 66 Mya.

Tectonics

During the Cretaceous, the supercontinent Pangaea continued to break apart into smaller landmasses. This led to the formation of the modern continents and the opening of the Atlantic Ocean.

Climate

The climate of the Cretaceous was generally warmer than today, with higher sea levels and no polar ice caps. This warm climate supported a rich diversity of life.

Paleontology

The Cretaceous is famous for its diverse and abundant life forms, particularly the dinosaurs.

Flora

The Cretaceous saw the rise of angiosperms (flowering plants), which began to dominate the landscape by the end of the period.

Fauna

Dinosaurs

The Cretaceous is known for a wide variety of dinosaurs, including the Tyrannosaurus rex, Triceratops, and Velociraptor.

Marine Life

The seas were populated by large marine reptiles such as Mosasaurus and Plesiosaurus, as well as ammonites and rudists.

Avian and Mammalian Evolution

Birds, which evolved from theropod dinosaurs, continued to diversify. Early mammals were small and mostly nocturnal.

Extinction Event

The Cretaceous ended with the Cretaceous–Paleogene extinction event, which led to the extinction of approximately 75% of Earth's species, including all non-avian dinosaurs. This event is widely believed to have been caused by a massive asteroid impact, evidenced by the Chicxulub crater in the Yucatán Peninsula.

See Also

• Jurassic Period
• Paleogene Period
• Mesozoic Era
• Dinosaur

External Links

• University of California Museum of Paleontology: The Cretaceous