Igneous Rocks: Formed from the cooling and solidification of molten rock (magma or lava). Examples include granite, basalt, and obsidian.
Sedimentary Rocks: Formed from the accumulation and cementation of sediments like sand, mud, and organic matter. Examples include sandstone, limestone, and shale.
Metamorphic Rocks: Formed from the transformation of existing igneous or sedimentary rocks due to intense heat and pressure. Examples include marble, slate, and gneiss.
Chemical Composition:
The Earth's crust is primarily composed of:
* Oxygen (O): 46.6%
* Silicon (Si): 27.7%
* Aluminum (Al): 8.1%
* Iron (Fe): 5.0%
* Calcium (Ca): 3.6%
* Sodium (Na): 2.8%
* Potassium (K): 2.6%
* Magnesium (Mg): 2.1%
Other Components:
* Trace elements: Including titanium, manganese, phosphorus, and many others.
* Water: Present in various forms, including groundwater, ice, and atmospheric water vapor.
Two Types of Crust:
The Earth's crust is divided into two types:
* Continental Crust: Thicker (35-70 km) and less dense, composed mainly of granite and other felsic rocks. It forms the continents.
* Oceanic Crust: Thinner (5-10 km) and denser, composed mainly of basalt and other mafic rocks. It forms the ocean floors.
Note: The composition of the Earth's crust can vary significantly depending on location and geological processes.
