Saturday, January 15, 2011

Before I forget_2

Mass extinction events

Disappearance of a large number of species in a small period of time
There are 5 major mass extinctions and several minor ones.
Mass extinctions interrupt the increase in species diversity over time.

1) P - T event / Permian Triassic Event

IS the largest mass extinction event
95% of the species and 50% of the families became extinct
Happened at the end of the Permian period of the Paleozoic Era 250 million years ago.
From the land amphibians , reptiles and ferns and gymnosperms 
From sea Trilobites , rugose and tubulate corals and brachiopods

Two reasons are given to explain this mass extinction

1) Climate Change

This is a slow process
Change of position of landmasses caused this.
During early Permian the movement of super continents
During late Permian and early Triassic formation of large super continent Pangea 
Formation of Ural Mountains caused erosion of sedimentary layer to low lands which caused destruction to many land animals and plants

2) Extensive volcanic activities

Earth's movement caused this.
Large amounts of SO2 was released to the Earth's atmosphere , which is toxic to animals and plants
Volcanic activities caused dust and ashes to gather in the atmosphere which caused sudden shading and cooling.

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