What is a Fossil

The term fossil describes a variety of artifacts from the distant past that are naturally preserved. In general, a fossil is any evidence of past plant or animal life that is preserved in the material of the Earth’s crust.

But when most people talk about fossils, they think that the fossil is the shape of an animal or a plant that has been preserved, while the actual organic matter of its body has disappeared. These incredible remnants, dating from prehistoric times, were formed very slowly by dynamic geological processes. That is only a part, a part of the group that is considered “fossil”.

Hóa thạch và những điều bí ẩn (phần 2)

In most cases, fossilization begins when a plant or animal dies and is quickly covered with sediment. Loose deposits protect the residual body from the elements, bacteria, and other forces that cause weathering and erosion. This slows down the decay process so that some remains (in most cases, only hard materials like bones or shells) are preserved for thousands of years. During this time, layers of sediment continue to penetrate the interior of the object. Eventually, these deposits become hard, solid rock that takes on the shape of the covered object.

Some time after this hard rock formed, water penetrated the rock and washed away the remains of the preserved object. Since the coatings are rigid, it does not collapse into the void where the object is penetrated by water and decomposed. This empty space forms a natural mold of the animal, perfectly preserving the shape of the original remains.

All the original organic material is gone, but nature has left an exact mineral replica of the plant or animal. In cases where the mineral doesn’t fill the mold, paleontologists can fill it in themselves, creating an artificial casting.

Of course, this is just one scenario of fossilization – there are all sorts of other ways that nature can make fossils. For example, a lot of prehistoric insects have been fossilized in amber. This type of fossilization occurs when the insect is encased in liquid sap from the tree. Like sediments on the bottom of water, tree sap protects insects from bacteria that decompose and eventually harden. Animal fossils are also found in pitches, swamps, quicksands and volcanic ash.


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