What Causes Extinctions? - Mass Extinctions

What causes extinctions?

 There are several threats of extinction for species in the world.

  • Disease.
  • Predators (wolf, lion, etc).
  • Disturbance of habitat (man made or climate change).
  • Chemicals (such as insecticide to control other populations).


 Mass extinctions are the wide spread and rapid decrease of biodiversity on earth. Currently, there are 5 mass extinctions recorded from 375 million years ago to present.

5 mass extinctions 

  • End Ordovian: 444 million years ago, 86% of species lost.
  • Late Devonian: 375 million years ago, 75% of species lost.
  • End Permin: 251 million years ago, 96% of species lost.
  • End Triassic: 200 million years ago, 80% of species lost.
  • End Cretaceous: 66 million years ago, 76% of species lost.
What causes mass extinctions?

There are 4 theories that scientists have created to explain the mass extinctions.

Catastrophic methane release: The release of methane gas that causes a temperature rise. It is caused by Methane Clathrate. This is an ice-like substance formed from water and methane in seabeds, arctic lakes and and permafrost. It is formed when temperature is at freezing and pressure of overlying water and sediment. This temperature rises causes stress to plants and animal life, which caused the mass extinction.

Flood basalt eruptions: This is a volcanic activity that is both large in scale and duration. It can occur in both the land or ocean. These eruptions can last for years and cover thousands of kilometres. This huge scale of lava affects climate by releasing sulphur dioxide and carbon dioxide which causes acid rain. this acid rain devastates areas and causes mass extinctions. 

Climate change: Maybe the most important theory affecting us this current day. This is where temperatures change from the ice age to deserts. Animals have no time to adapt to any of the new climates, therefore causing a mass extinction. 

Impact events: When the plant is struck by a comet or meteor large enough to create a huge shock wave all around the world. This causes a dust of debris rain around the world which destroys species' climates. Without habitats, the animals weren't able to survive and creates a mass extinction.

 Sources:
http://www.bbc.co.uk/nature/extinction_events
http://www.bbc.co.uk/nature/extinction_causes



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