Description of the Event

The Cretaceous-Tertiary extinction event occurred roughly 65 million years ago when an asteroid struck Earth. It caused major environmental impacts and loss of life, leading to the extinction of between 60% and 80% of all species on Earth.

Climate

The Earth’s surface drastically heated up to hundreds of degrees after the asteroid impact. Temperatures dropped for several months afterwards due to particles that were tossed into the atmosphere by the impact blocking the sunlight from reaching the surface.

Vegetation

Due to limited sunlight, photosynthesis was disrupted and vegetation had a difficult time growing, leading to even more species dying out.

Natural Elements

The impact entirely changed Earth’s evolutionary history. The extinction of the dinosaurs led to the rise of larger and stronger mammals such as the ancestors of humans to emerge.

Extinct Dinosaurs

Type	Image	Description
Theropods		Theropods were a group of bipedal dinosaurs that included species such as the Velociraptor and Tyrannosaurus rex. They were primarily carnivorous, with some later evolving into omnivores and herbivores. They first appeared in the Triassic period and existed until the asteroid hit Earth.
Sauropods		Sauropods were long-necked herbivores. They included species such as the Brachiosaurus and Diplodocus. They were some of the largest animals to ever live. They existed from the Triassic period until the Cretaceous-Tertiary event. Sauropod fossils have been discovered on every continent.
Ankylosaurs		Ankylosaurs were a group of herbivores including species such as the Ankylosaurus and Euoplocephalus. They existed during the Late Jurassic period until the end of the Cretaceous period. Ankylosaur fossils have been discovered in North America, Europe, and Asia.
Ornithopods		Ornithopods were a group of bipedal and quadrupedal herbivores. The group included species such as the Iguanodon and Parasaurolophus. They existed from the Late Jurassic period to the end of the Cretaceous period. Ornithopod fossils have been uncovered on every continent.
Ceratopsians		Ceratopsians were a group of herbivores including species such as the Triceratops and Styracosaurus. They existed during the Late Cretaceous period. Ceratopsian fossils have been found primarily in North America and Asia.
Pachycephalosaurs		Pachycephalosaurs were a group of herbivores including species such as the Pachycephalosaurus and Stegoceras. They lived during the Late Cretaceous period. Pachycephalosaur fossils have been found mainly in North America and Asia.

How did Species Survive?

Most species that survived the direct impact burrowed underground where it would be safe for them to live. Fossils show that worms were among the first species to emerge from their underground burrows to begin living on the surface again.

Types of Fossils