Lithosphere

Lithosphere is the solid outermost layer of a terrestrial-type planet or natural satellite that is defined by its rigid mechanical properties. On Earth, it extends from the base of the mantle to about 60 kilometers above the surface. The term “lithosphere” comes from Ancient Greek λίθος (líthos), meaning “stone”, and σφαῖρα (sphaira), meaning “sphere”.

The study of lithospheric evolution requires consideration of both processes that occur at its boundaries and those that occur within its interior. At the boundary with the atmosphere, weathering and erosion break down rocks and soils into smaller particles that are transported away by wind, water, or ice. This process helps to sculpt landforms such as mountains, valleys, and plains. Within the lithosphere, deformation occurs in response to stress; this can take the form of Earthquakes at plate boundaries or folding and faulting within mountain belts. Both types of deformation help shape landscapes. In addition, heat flow from Earth’s interior drives convection within the mantle, which influences lithospheric dynamics. Plate tectonics is perhaps the most important factor controlling lithospheric evolution; it determines how rocks are distributed across Earth’s surface and how they interact with each other over time.

Rocks making up Earth’s crust consist primarily of minerals—inorganic compounds with a crystalline structure—and are classified according to their composition: igneous rocks originate from magma (molten rock); sedimentary rocks form when bits of rock and organic material become cemented together; metamorphic rocks result when either type of rock changes due to high temperature or pressure conditions found deep below Earth’s surface. Most rocks fall into one of these three categories; however, some contain a mixture of two or more types (for example, granite consists mostly of quartz crystals cemented together by feldspar).

Igneous rocks make up most of Earth’s continental crust as well as its ocean floor; they also form much of the material ejected during volcanic eruptions. When magma cools rapidly on Earth’s surface it forms glassy obsidian or black basalt; if cooling is slower then light-colored granite may result. Igneous rocks can also be classified according to their texture—that is, whether they consist mostly of large grains (coarse-grained) or small ones (fine-grained). Coarse-grained igneous rocks have visible crystals whereas fine-grained ones do not; examples include basaltic lava flows versus rhyolitic ash deposits respectively