How fossils form
Describe in simple terms how fossils are formed when things that have lived are trapped within rock over millions of years
What a learner can do afterwards
- Describe the basic process: organism dies, gets buried in mud/sand, layers build up, material turns to rock over millions of years
- Explain that the organism's shape is preserved as a fossil within the rock
- Give examples of common fossils (shells, bones, leaf imprints, footprints)
The lesson
A fossil is the shape of a plant or animal that lived a very long time ago. It did not turn to dust like most living things do. Instead, its shape got trapped inside rock, and you can still see it today.
Fossils start when a living thing dies and falls into soft mud or sand, often at the bottom of a lake or sea. Over many years, more mud and sand pile up on top of it, layer after layer. All that weight presses down hard, and slowly the mud turns into solid rock.
A seashell falls onto the sea floor and gets covered in mud. Over millions of years, the mud around it hardens into rock, and the shell's exact shape stays pressed inside. When someone breaks open that rock today, they find a shell fossil.
Fossils are not only bones. Shells, leaf prints, and even footprints left in old mud can all turn into fossils too, as long as they get buried and pressed for a very long time.
A fossil forms when something that died gets buried under layers of mud, which slowly turns to rock and keeps the shape inside for millions of years.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.