1. Crust:
* The outermost layer, thin and solid, composed of various types of rocks.
* Divided into two types:
* Oceanic crust: Dense, thinner, and primarily made of basalt (a dark, fine-grained volcanic rock).
* Continental crust: Less dense, thicker, and primarily composed of granite (a light-colored, coarse-grained igneous rock).
* Home to all life and human activity.
2. Mantle:
* Largest layer, extending from the base of the crust to about 2,900 kilometers (1,800 miles) below the surface.
* Composed of mostly solid rock, but can behave like a very viscous fluid over long periods due to high pressure and temperature.
* Source of magma, which rises to the surface through volcanic eruptions.
* Responsible for plate tectonics - the movement of the Earth's crustal plates.
3. Outer Core:
* Liquid layer, located about 2,900 to 5,150 kilometers (1,800 to 3,200 miles) below the surface.
* Primarily composed of iron and nickel, with trace amounts of other elements.
* Generates the Earth's magnetic field, which protects us from harmful solar radiation.
4. Inner Core:
* Solid ball, about 1,220 kilometers (758 miles) in radius, located at the Earth's center.
* Composed mostly of iron with some nickel, with temperatures reaching over 5,200° Celsius (9,392° Fahrenheit).
* Extreme pressure keeps the inner core solid despite the high temperature.
Additionally, there are two important boundaries within the Earth:
* Mohorovičić discontinuity (Moho): The boundary between the crust and mantle, characterized by a sharp increase in seismic wave velocity.
* Gutenberg discontinuity: The boundary between the mantle and the outer core, characterized by a sharp decrease in seismic wave velocity.
Understanding the Earth's layers is crucial for studying various geological phenomena like earthquakes, volcanoes, and plate tectonics. It also provides insights into the Earth's formation and evolution over millions of years.
