1. Igneous Rocks:
- Igneous rocks are formed by the cooling and solidification of molten rock materials (magma or lava).
- Magma cools within the Earth's crust to form intrusive igneous rocks (plutonic rocks) while lava cools on the Earth's surface to form extrusive igneous rocks (volcanic rocks).
- Examples of igneous rocks include granite (intrusive), basalt (extrusive), and obsidian (extrusive).
2. Sedimentary Rocks:
- Sedimentary rocks are formed from the accumulation of sediments composed of various materials derived from the weathering and erosion of pre-existing rocks, and organic matter.
- Sediments accumulate in low-energy environments like basins, oceans, rivers, or lakes. Through compaction (pressure) and cementation (precipitation of minerals), these sediments are then consolidated and transformed into sedimentary rocks.
- Examples of sedimentary rocks include sandstone (from sand sediments), limestone (from calcium carbonate sediments), and shale (from clay sediments).
3. Metamorphic Rocks:
- Metamorphic rocks are formed from pre-existing rocks (igneous, sedimentary, or metamorphic) that undergo substantial changes in their physical and mineral composition due to high temperature, high pressure, and the presence of chemical fluids without complete melting.
- Metamorphic processes occur during deep burial within the Earth's crust or during regional mountain-building events (orogenies).
- Common metamorphic rocks include slate (derived from shale), marble (from limestone), schist (from mudstone), and gneiss (from granite).