If one ever goes to the beach, one can find many shells. This is assuming that said persons are looking for shells. Shells can be found in other places such as rivers and lakes. Anywhere a mollusk can inhabit, so can shells be found. However, there is more.
Fossils of shells have been found in many places. Fossils tell alot about what kinds of animals and plants existed in the past. Sit and thing about this. One can kind shells. Those shells were not there by accident. Someone once lived in that shell. Either the animal left that shell, or it was extracted from that shell. The shells that we see today could be the fossils some scientists find thousands of years from now. The earth’s physical processes can turn today’s shells into fossils. Think about the fossils we find today. They were once living things a long time ago.
All of that is in the future. However, looking towards the future is important in the earth sciences. This in addition to looking at the past and at today.