Rocks
There are 3 types of rocks.
- Igneous
- Formed when molten rock (magma) cools and hardens. It comes in two types: intrusive (when cooling takes place slowly beneath earth's surface) and extrusive (when cooling takes place rapidly on earth's surface.
- Examples include basalt and obsidian.
- Formed when rocks are changed into different kinds of rocks by great heat and/or pressure. They are heated, squeezed, folded, or chemically changed by the contact of hot fluids.
- Examples include slate, gneiss, and marble.
- Formed from the compaction and/or cementation of rock pieces, mineral grains, or shell fragments called sediments.
- Formed through the weathering and erosion of rocks exposed.
- Examples include sandstones.