Fossils are the remains of organisms from many years ago, which are found in rocks. Fossils provide the evidence that organims lived years ago. Fossils form in rocks in three ways:
1. From GRADUAL REPLACEMENT by minerals (most fossils happen this way)
- Things like teeth, shells, bones, etc... which don't decay easily, can last a long time when buried.
- They're eventually replaced by minerals as they decay, formining a rock-like substance shaped like the original hard part.
- The surrounding sediments also turn to rock, but the fossil stays distinct inside the rock and eventually digs it up.
2. From CASTS and IMPRESSIONS
- Sometimes, fossils are formed when an organism is buried in a soft material like clay. The clay then hardens around it…