Key Concepts

1. Sedimentary rock is formed over millions of years from the deposition of sediment in layers. Sediment layers on top apply pressure to those on bottom, compacting them into sedimentary rocks. 

2. Fossil fuels are formed over millions of years from the deposition of organic materials in layers. Organic matter in bottom layers begins to decay from the pressure and heat generated from the layers above them.

3. Fossil fuels are formed in sedimentary rock layers when materials are compressed and heated deep under the Earth’s surface.