How Fossil Forms

How Fossils Form

Follow the journey of a dinosaur through time to see how it becomes a fossil.


A dinosaur dies near water

Stage 1: Death & Deposition. An organism dies and its remains are left on the ground or underwater. For a fossil to form, the remains must be covered quickly to protect them from scavengers and decay.

Buried in layers of sediment

Stage 2: Sedimentation. Over time, the organism is buried by deep layers of mud, sand, and silt. These layers (sediment) protect the remains from being completely destroyed.

Bones turning to stone

Stage 3: Mineralization. Water seeps through the sediment, carrying minerals. The soft parts of the body rot away, but the minerals fill the tiny holes in the bones, eventually turning them into solid stone.

Sediment hardening into rock

Stage 4: Lithification. Over millions of years, the immense weight and pressure of the upper layers turn the bottom layers of sediment into solid rock. The fossil is now safely locked inside.

Erosion reveals the fossil

Stage 5: Uplift & Discovery. Earth’s movement and erosion (wind/rain) eventually bring the rock layers back to the surface. A paleontologist finds the fossil and carefully digs it up!