Rocks and fossils: a window into the past
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What you will learn
By the end, you can name the three rock types and describe how a fossil forms.
A long-dead sea creature sank into soft mud. Over millions of years, the mud turned to rock and the creature left a perfect stone copy: a fossil.
Read the explanation
Rocks come in three types. Igneous rock forms when hot melted rock cools. Sedimentary rock forms in layers as sand and mud settle and press together. Metamorphic rock forms when heat and pressure change an older rock. Fossils usually form in sedimentary rock, when a buried plant or animal is slowly replaced by minerals.
- Igneous = cooled from hot melt.
- Sedimentary = layers pressed together.
- Metamorphic = changed by heat and pressure.