Mass Extinction: What Happened?

Part of the Dinosaurs: Ancient Fossils, New Discoveries exhibition.

What happened to cause such widespread devastation 65 million years ago?

The Hunt for a Culprit

Scientists agree that species go extinct primarily as a result of changes in their environment. The extinction of many species around the world at one time reflects large-scale changes in the global environment.

To explain what caused this mass extinction, scientists have focused on events that would have altered our planet's climate in dramatic, powerful ways. The leading theory is that a huge asteroid or comet slammed into Earth 65 million years ago, blocking sunlight, changing the climate and setting off global wildfires. In recent years, however, researchers have also been investigating whether other forces, including massive volcanic eruptions and changes in sea level, may have contributed to the general environmental decline.

Article Chaos in the Cretaceous! A wide range of plants and animals, both on land and in the sea, went extinct 65 million years ago. The ferocious Tyrannosaurus rex... Article Mass Extinction Around 65 million years ago, something unusual happened on our planet-and we can see it in the fossil record. Fossils that are abundant... Article Missing Marine Life Large dinosaurs like T. Rex are the most famous creatures that went extinct some 65 million years ago. But a wide range of other... Article Final Days Around 66 million years ago, a wide range of large dinosaurs roamed the continents, while winged reptiles called pterosaurs flew... Article Impact In the late 1970s a group of researchers led by physicist Luis Alvarez and geologist Walter Alvarez made an important discovery.... Article Volcanoes Some researchers think that intense volcanism could have contributed to the dinosaurs' decline well before a comet or asteroid impact... Article End of an Era Our view of the mass extinction 65 million years ago is somewhat hazy, thanks to the unavoidable limitations of the fossil record.... Article Discarded Theories Paleontologists are actively investigating what caused all nonavian dinosaurs to die out 65 million years ago. Most agree that the... Article Survivors Global forest fires. Acid rain. Tsunamis. Skies dark for months or years with volcanic ash. How could anything have survived? Roughly... Article Dinosaurs Survive! Not all dinosaurs died out 65 million years ago. Article Survival in the Seas A variety of species in the world's oceans, from microscopic organisms to large sharks, survived the mass extinction 65 million years...