sentence: Pressure turns it all into hard rock.
sentences_before: A low-lying tropical swamp or rain forest forms a peat swamp which is short of oxygen. Dead plant material builds up, and does not decompose entirely. The plant material gets buried as a peat bog. From time to time rivers bring down a load of sediment from nearby mountains, covering the swamp. Eventually layers of coal alternate with layers of sandy deposit.
sentences_after: Later on, the rocks are uncovered by erosion, and fossils can be found by humans.
concept_name: pressure
headings: Mazon Creek Palaeoecology
categories: Lagerstätten