Which type of rock is most likely to contain fossils?

• A. Sedimentary rocks
• B. Igneous rocks
• C. Metamorphic rocks
• D. Igneous rocks with fossils

Answer: (A)

Fossils survive best in sedimentary rocks. These rocks form from layers of sediment that settle in places like rivers, lakes, and oceans. When organisms die, their shells, bones, or imprints can get buried by more sediment. Over time, the sediments are compacted and cemented into rock, and the remains may be preserved through processes like mineral replacement, leaving behind a fossil. The relatively gentle conditions at shallow depths help keep shape and details intact.

Igneous rocks form from molten material that cools, which involves high heat that would burn or melt any living material, so fossils don’t survive there. Metamorphic rocks originate under heat and pressure that change minerals and textures, often flattening or destroying fossils. The idea of fossils in igneous rocks isn’t typical, since the formation conditions don’t favor preserving ancient remains.