describe how fossils are may be formed?

Question

fossils

Answer 1

Objects or animals that die in a situation that keeps oxygen from getting to them can eventually have minerals replace the carbon.

In some cases the mud hardens and there is a hole where the object was that can be filled. You can do this yourself by putting a leaf on wet concrete, though replacing the carbon with minerals is much to slow to watch.

One very fast way for fossils to form is when a volcano erupts, and very hot ash that has minerals still involved drops on whatever is unlucky to be standing about under the ash fall.

Throughout the American west are large areas of forest turned to petrified wood by exploding volcanoes, sometimes layer after layer, as new forests grew up and a few thousand years later the volcano explodes again, and then again etcetera.

Obviously these situations are very rare, so only a very tiny percentage of living things are made into fossils.

Answer 2

The best way is when they die covered in mud. Eventually such mud becomes part of a geologic layer. With time the bone tissues may be replaced by other minerals.
Another way is to die in a very dry place, such as a desert, and again as above.
There is even a better way. To die in a glacier, in which case also the flesh is preserved. They recently found a very well preserved body of a prehistoric man in the Alps, between Austria and Italy.