After the animal or plant dies, bacteria that decompose the tissues are taken over. It takes some time and nothing remains of the corpse of an animal or a dried plant.
The decay process lasts from several months to several years. But there are times when dead plants and animals fall into favorable conditions, then hard tissues - bones, shells, teeth - last for a very long time.
Why can bones survive?
Imagine the joy of a paleontologist who has found a tooth in the earth that is 3 million years old! This find is called a fossil. It can be a real preserved tooth, a genuine bone or a surviving shell, preserved for centuries in the ground. Most often, the fossil remains of ancient marine animals are found, because their remains quickly sink into the muddy bottom, and the bodies of land animals remain not buried, and therefore the process of decay quickly begins.
Types of Fossils
- Imprints of hard fabrics. There may be imprints of hard tissues in petrified sedimentary rocks, for example, the skeleton of a small marine animal carved in stone.
- Mineral copies of bones, teeth, and shells. Another type of fossil - fossils in the full sense of the word - mineral copies of bones, teeth and shells.
What should happen to keep the fossils?
In order for the earth to create a fossil, allowing us to see what the antediluvian earthly creatures looked like, some conditions must be observed, the most important of which are that the remains should be protected from wind and rain.This occurs when an animal enters sedimentary rock deposits - sand or gravel. The ash layer is also a good and reliable coating, contributing to the formation of fossils.
Sedimentary deposits with fossilized remains of living things are sometimes found in lakes, swamps and caves. But the most common places for detecting fossils are land areas with increased geological activity, that is, near erupting volcanoes or near growing young mountains. Himalayas rising to the skies are growing mountains, part of the land reared by the clash of the Hindustan subcontinent with the mainland of Asia.
Fragments of rocks and soil crumble from the slopes of growing mountains into rivers that carry these sedimentary rocks into the oceans. Most of the fossils are found at the bottom of ponds or former ponds. Such fossils are reliably covered by geological deposits, which protects them from bacteria that freely reproduce on the land surface.
Interesting fact: fossils can be real teeth, bones, shells of animals or their imprints on a stone or their stone copies.
How are fossils formed?
Fossil remains are formed in many ways. Mineral salts can penetrate the pores of decaying bones and crystallize there, protecting the bones from further decay. Acids can dissolve bones or shells, leaving a cavity in the petrified rock that exactly matches these bones and shells in shape. It happens that these cavities are filled with crystallizing solutions of mineral salts.
After crystallization, the salts precipitate and an exact stone copy of the fossil bone or shell is obtained. Fossils come in all sizes - from huge ones, such as the thighbones of a tyrannosaurus, to tiny ones. A geological student found a fossilized dinosaur embryo in Colorado - that is, a dinosaur cub that has not hatched yet from an egg. This embryo is approximately 135 to 150 million years old. Well preserved bones of the paws, part of the spine and lower jaw. Two milk teeth protrude from it. Scientists believe that a small dinosaur died before it had time to hatch from an egg.
