1. Crust:
* Thickness: 5-70 km (3-44 miles)
* Composition: Primarily composed of igneous, sedimentary, and metamorphic rocks. The oceanic crust is thinner and denser than the continental crust.
* Characteristics: The crust is the solid, outermost layer where we live and interact with the Earth. It's relatively brittle and fractured.
2. Mantle:
* Thickness: ~2900 km (1800 miles)
* Composition: Primarily composed of silicate minerals, mostly peridotite.
* Characteristics: The mantle is the largest layer by volume. It's mostly solid but behaves like a very viscous fluid over long periods. Convection currents within the mantle drive plate tectonics.
3. Outer Core:
* Thickness: ~2200 km (1400 miles)
* Composition: Primarily composed of liquid iron and nickel, with trace amounts of other elements.
* Characteristics: The outer core is liquid due to immense pressure and heat. The movement of molten iron generates Earth's magnetic field.
4. Inner Core:
* Thickness: ~1220 km (760 miles)
* Composition: Primarily composed of solid iron and nickel.
* Characteristics: The immense pressure at the Earth's core prevents the iron from melting, even though the temperature is extremely high.
Key Points:
* Temperature: Temperature increases with depth, from around 20°C (68°F) at the surface to over 5,200°C (9,392°F) at the core.
* Pressure: Pressure also increases with depth, reaching immense levels at the core.
* Seismic Waves: We learn about the Earth's interior by studying how seismic waves from earthquakes travel through it. Different layers have different densities and compositions, causing the waves to bend and change speed.
Visualizing the Layers:
Imagine a hard-boiled egg. The shell is like the crust, the white is like the mantle, and the yolk is like the core. Of course, the Earth's structure is far more complex than a simple egg analogy, but it provides a helpful visual.
