Formation of Rocks
Formation of Rocks
Introduction to Rocks
- Rocks are comprised of minerals and are formed through various processes over millions of years.
- These processes include: weathering, erosion, compaction, deposition, and crystallisation.
- There are three major classes of rocks: Igneous, Sedimentary and Metamorphic.
- Each class of rocks is formed through distinct processes.
Igneous Rocks Formation
- Igneous rocks are formed when magma or lava cools and solidifies.
- The cooling could either happen underneath the Earth's crust (intrusive igneous rocks) or on the surface (extrusive igneous rocks).
- The rate of cooling can affect the size of crystals in the rock: slower cooling results in larger crystals.
- Examples of igneous rocks include granite, basalt, and obsidian.
Sedimentary Rocks Formation
- Sedimentary rocks are formed from the sediments of other rocks.
- These sediments are carried by water, wind or ice and deposited in layers over time.
- Over time, these layers are compressed and cemented together, forming sedimentary rocks.
- These rocks often contain fossils, providing valuable insight into Earth's history.
- Examples include sandstone, limestone, and shale.
Metamorphic Rocks Formation
- Metamorphic rocks are formed when existing rocks are subjected to high temperatures and pressure over time.
- This process, known as metamorphism, can alter the mineral composition and structure of the rock.
- Metamorphic rocks can be derived from igneous, sedimentary, or even other metamorphic rocks.
- Examples include marble, slate, and gneiss.