Cretaceous

The Cretaceous Period is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, following the Jurassic Period and preceding the Paleogene Period of the Cenozoic Era. The Cretaceous is notable for being the longest period of the Phanerozoic Eon, lasting approximately 79 million years.

Geological Characteristics

The Cretaceous Period is characterized by high sea levels and the development of extensive shallow inland seas. These seas were home to a diverse array of marine life, including ammonites, belemnites, and rudists. The period also saw the breakup of the supercontinent Pangaea, leading to the formation of the modern continents.

Tectonics

During the Cretaceous, the movement of tectonic plates was significant. The Atlantic Ocean continued to widen as North America and Eurasia drifted apart. The Indian Plate began its northward journey towards the Asian Plate, which would eventually lead to the formation of the Himalayas in the Cenozoic Era.

Climate

The climate of the Cretaceous was generally warm, with little to no polar ice. This warm climate supported lush vegetation and a wide variety of dinosaur species. The high levels of carbon dioxide in the atmosphere contributed to the greenhouse conditions of the period.

Flora and Fauna

The Cretaceous Period was a time of significant evolutionary change. It saw the rise of angiosperms (flowering plants), which began to dominate the landscape. These plants provided new food sources for herbivorous dinosaurs and other animals.

Dinosaurs

Tyrannosaurus rex, one of the most famous dinosaurs of the Cretaceous.

The Cretaceous is perhaps best known for its diverse and abundant dinosaur fauna. Iconic dinosaurs such as Tyrannosaurus rex, Triceratops, and Velociraptor roamed the Earth during this time. The period also saw the evolution of birds from small theropod dinosaurs.

Marine Life

Mosasaurus, a large marine reptile of the Cretaceous seas.

The Cretaceous seas were teeming with life, including large marine reptiles like mosasaurs, plesiosaurs, and ichthyosaurs. Invertebrates such as ammonites and belemnites were also abundant.

Extinction Event

The Cretaceous Period ended with one of the most significant mass extinctions in Earth's history, known as the Cretaceous–Paleogene extinction event. This event led to the extinction of approximately 75% of Earth's species, including all non-avian dinosaurs. The leading hypothesis for this extinction is the impact of a large asteroid or comet in the region of present-day Chicxulub in Mexico.

Related Pages

• Mesozoic Era
• Jurassic Period
• Paleogene Period
• Dinosaur
• Mass extinction