How many mass extinctions happened in earth?

Earth has experienced five major mass extinction events, with the most recent occurring 66 million years ago, when the dinosaurs went extinct.

Scientists believe we are currently in the midst of a sixth mass extinction, driven by human activities. 

The "Big Five" Mass Extinction Events:

• Late Ordovician Extinction (443 million years ago):

  A significant loss of marine species, including a large portion of corals and trilobites. 

• Late Devonian Extinction (374 million years ago):

  This event caused a significant loss of marine species, particularly in tropical regions. 

• Permian-Triassic Extinction (252 million years ago):

  The most devastating mass extinction in Earth's history, with over 95% of species wiped out, including many marine invertebrates and amphibians. 

• Triassic-Jurassic Extinction (201 million years ago):

  This event saw the extinction of many marine reptiles, amphibians, and large land reptiles. 

• Cretaceous-Paleogene Extinction (66 million years ago):

  The extinction of the non-avian dinosaurs and other large land and sea animals, paving the way for the rise of mammals and birds. 

The Sixth Mass Extinction:

• The current period of rapid biodiversity loss, primarily driven by human activities like habitat destruction, climate change, pollution, and overexploitation of resources.