Rocks are classified into three main types based on their formation processes: igneous, sedimentary, and metamorphic. Here’s a brief overview of each type, how they are formed, and some examples:
1. Igneous Rocks
Formation: Igneous rocks form from the solidification of molten material called magma (below the Earth’s surface) or lava (on the surface).
Examples:
- Granite: A coarse-grained rock formed from slow cooling of magma beneath the Earth's surface.
- Basalt: A fine-grained rock that forms when lava cools quickly on the Earth's surface.
2. Sedimentary Rocks
Formation: Sedimentary rocks are formed from the accumulation and compaction of mineral and organic particles, as well as the precipitation of minerals from solution. They typically form in layers.
Examples:
- Sandstone: Formed from compacted sand grains.
- Limestone: Often formed from the accumulation of shells, coral, and other calcareous materials.
3. Metamorphic Rocks
Formation: Metamorphic rocks originate from existing igneous, sedimentary, or other metamorphic rocks that have undergone a transformation due to heat, pressure, or chemically active fluids.
Examples:
- Schist: Formed from the metamorphism of shale, characterized by its layered appearance.
- Gneiss: Often derived from granite or sedimentary rock, it exhibits banding due to the segregation of mineral grains under high temperature and pressure.
These classifications help in understanding the geological processes that shape our planet and the materials that make up its structure.