what is Fossils. Diefinition and types of fossils

Fossil:

•   Meanings:

           Fossa (latin)  means "Pit". So, something which is dug out is called Fossil.

•   Definition:

            A true fossil is the  one which is dug out and is 20,000 years old.

•   How 20,000?
         We can assign the age of a fossil by " U-Pb-Dating" through half life of 4.5 thousand years 

                                                  OR
                    By " Carbon-Dating"  with half life of 5567 years.
Index Fossil:
          The fossil which has wide horizontal and short vertical distribution. Examples are Plesiosaurus, Archaeopteryx 

Extinction Of Dinosaurs:

There are many theories about the extinction of Dinosaurs.According to some scientists that the emergence of big mountain systems (such as Himalayan mountain system , Alps and Andes etc.) caused change in topography of the world. The uprise of mountains caused climatic changes especially the change in temperature. As we know that the all dinosaurs were cold blooded creatures that means that they could not tolerate a slight change in temperature. In addition to this the floral change from Gymnosperms to Angiosperms  in Cenozoic and late Mesozoic caused scarcity of their strict good Gymnosperms. Hence they died of hunger also. In addition to this the emergence of Mammals had a great impact on the extiction of dinosaurs. The Mammals used to eat the eggs of dinosaurs. ( i feel great pity on them).

Fossiliferous Rocks:
Those rocks which contain fossils are called Fossiliferous Rocks. The earliest fossils on the earth are the stromatolites that consist of rock built from layer upon layer of sediments and other precipitants.

Why Fossils Are RARE?

Fossilization is an exceptionally rare occurrence, because most components of formerly living things tend to decompose relatively quickly following death. In order for an organism to be fossilized, the remains normally need to be covered by sediment as soon as possible. However there are exceptions to this, such as if an organism becomes frozen, desiccated, or comes to rest in an anoxic (oxygen-free) environment. There are several different types of fossils and fossilization processes.


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