Question: how are fossils formed

Gemma Cripps answered on 11 Nov 2015:

Hi Ebony,

I looked this one up 🙂
•Some animals are quickly buried after their death (by sinking in mud, being buried in a sand storm, etc.).
•Over time, more and more sediment covers them.
•The parts of the animals that didn’t rot (usually the harder parts likes bones and teeth) are encased in the newly-formed sediment.
•In the right circumstances (no scavengers, quick burial, not much weathering), parts of the animal turned into fossils over time.
• After a long time, the chemicals in the buried animals’ bodies undergo a series of changes. As the bone slowly decayed, water with minerals seep into the bone and replace the chemicals in the bone with rock-like minerals. The process of fossilization involves the dissolving and replacement of the original minerals in the object with other minerals (and/or permineralization, the filling up of spaces in fossils with minerals, and/or recrystallization in which a mineral crystal changes its form).
•This process results in a heavy, rock-like copy of the original object – a fossil. The fossil has the same shape as the original object, but is chemically more like a rock! Some of the original hydroxy-apatite (a major bone) remains, although it is saturated with silica (rock).