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Platecarpus ptychodon 25-35mm
The mantle is the part of the earth between the Earth's crust and the core. The top of the mantle is defined by the Mohorovi?i? discontinuity. The mantle is the largest part of the volume of the earth because the core is relatively small and the crust relatively thin. The Earth's mantle is about 2900 kilometres thick. The top layer of the mantle together with the Earth's crust is called the lithosphere. Beneath that lies the asthenosphere.
Considering the fact that drilling in the Earth's mantle is impossible, seismolgy is used to examen it. By measuring the resonance of seismic waves the different densities of materials in the mantle can be determined. The mantle mainly consists of olivine and different types of pyroxene, both are minerals.
The upper part of the mantle is plastic because temperature lies above 1000 degrees Celcius and the pressure is relatively low. Because of that the plates of the Earth's crust 'float' on the mantle. The rock in the upper layer of the mantle partly melts and becomes magma. This magma reaches the surface of the earth because of vulcanic activity.
Radioactive elements that have been part of the core of Earth from the formation on decay and produce heat in that process. Because the rock in the mantle plastically deforms and the core produces heat there is a convective circulation of material. This circulation transports hot material upward. This causes tectonic movement of plates. Some places lie over mantle plumes where hot material from within the mantle leaks to the surface of the earth. These places are called hotspots.
A schematic representation of the inside of the Earth. 1 Continental crust, 2 Oceanic crust, 3 and 4 Earth's mantle 5 Outer core (liquid), 6 Inner core (solid), A Mohorovi?i? discontinuity, B Gutenberg discontinuity, C Lehmann discontinuity. Creative Commons License.
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