Fig. 1.5. 3D model of the geoid shape (www.sensoryoutput.com)
1.4. 1.4. Materials of the lithosphere – petrological bases
The lithosphere is the rigid outermost shell of the Earth. It comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater. The lithosphere is underlain by the asthenosphere, the weaker, hotter, and deeper part of the upper mantle. Rocks of the lithosphere are generally classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into igneous, sedimentary, and metamorphic(Fig. 1.6.).
Fig. 1.6. The rock cycle
1.4.1. 1.4.1. Igneous rocks
Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition (Fig. 1.7.).
Share with your friends: |