The eight commonly occurring elements that are found in Earth's lithosphere include oxygen, silicon, calcium, sodium, magnesium, aluminum, potassium and iron. The crust, which forms part of the lithosphere, contains around 80 chemical elements that are present in varying amounts in approximately 2,000 minerals and compounds.
Earth is stratified based on two criteria: chemical constitution and degree of rigidity. The planet has three compositional layers and five mechanical layers. The compositional layers include the crust, mantle and core. The lithosphere, asthenosphere, mesosphere, outer core and inner core comprise the mechanical layers.
The lithosphere pertains to the rigid, uppermost mechanical layer, which consists of the crust and topmost portion of the mantle. Its average thickness is measured at around 62 miles. The lithosphere is broken into massive continental and oceanic plates that are constantly sliding, gliding and grinding against each other. The variety of minerals and rocky materials that form on these plates are the products of geological processes.
Some of the most abundant minerals found on the crust include quartz, hematite and orthoclase. Quartz is composed of silicon and oxygen; hematite is made up of iron and oxygen; and orthoclase is a potassium aluminum silicate compound. The chemical combination of one or more minerals produce rocks. The general elemental composition of rocks mainly include silicon, oxygen, aluminum, calcium, potassium and sodium. Other elements present in crustal rocks in minute amounts include titanium and hydrogen.