Structure of the Earth
Internal Structure of the Earth is layered in spherical shells, an outer silicate solid crust and mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. Scientific understanding of the internal structure of the Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of the gravitational and magnetic fields of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth’s deep interior.
Different layers of the Earth
Our Earth consists of four different layers they are namely as:
- Inner core
- Outer core
1. Inner Core: It is the center and the hottest layer of the Earth. The inner core is solid and made up of iron and nickel with temperature up to 5,500oC. Due to its immense heat energy, the inner core is more like the engine room of the Earth.
2. Outer Core: The outer core of the Earth is similar to a very hot ball of metals, whose temperature is around 4000 oF to 9000oF. It is so hot that the metals inside are all in the liquid state. The outer core is located around 1800 miles under the crust and approximately 1400 miles thick. It is composed of metals such as iron and nickel. The outer core surrounds the inner core.
The inner core has pressures and temperatures so high that the metals are squeezed together and not able to move like a liquid, but are forced to vibrate instead of solid.
3. Mantle:Earth’s mantle extends to a depth of 2,890 km, making it the thickest layer of Earth. The mantle is divided into upper and lower mantle. The mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust.Although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales. Convection of the mantle is expressed at the surface through the motions of tectonic plates. As there is intense and increasing pressure as one travels deeper into the mantle, the lower part of the mantle flows less easily than does the upper mantle (chemical changes within the mantle may also be important). The viscosity of the mantle ranges between 1021 and 1024Pa·s, depending on depth.
4. Crust: The Earth’s crust ranges from 5–70 kilometres in depth and is the outermost layer. The thin parts are the oceanic crust, which underlie the ocean basins 5–10 km and are composed of dense (mafic) iron magnesium silicate igneous rocks, like basalt. The thicker crust is continental crust, which is less dense and composed of sodium potassium aluminium silicate rocks, like granite.
Many rocks now making up Earth’s crust formed less than 100 million years ago; however, the oldest known mineral grains are about 4.4 billion years old, indicating that Earth has had a solid crust for at least 4.4 billion years.