Fossils

• Fossils are the remains of organisms many years ago that are found in rocks
• Gradual replacement by mineral:

  • things like teeth, shells and bones don't decay easily can last long when buried
  • they're eventually replaced by minerals forming rock like substances
  • the fossil stays distinct inside the rock and eventually is dug up
• Casts and impressions:

  • fossils form when an organism is buried in a soft material like clay . The clay hardens around it and the organism decays leaving a cast of itself