The Earth's crust is primarily composed of solid rock materials. It is the outermost layer of the Earth, ranging in thickness from about 5 to 70 kilometers (3 to 44 miles). The crust is divided into two main types: continental crust and oceanic crust.
Continental crust: The continental crust forms the landmasses and continents. It is thicker, with an average thickness of about 30 to 50 kilometers (19 to 31 miles). Continental crust consists mainly of granite, a light-colored igneous rock that is rich in silica, aluminum, and potassium. Granite is less dense than the rock found in the oceanic crust.
Oceanic crust: The oceanic crust lies beneath the oceans. It is thinner, ranging from about 5 to 10 kilometers (3 to 6 miles) in thickness. Oceanic crust is primarily composed of basalt, a dark-colored igneous rock that is rich in iron and magnesium. Basalt is denser than granite and is formed from solidified lava that has erupted from underwater volcanoes.
In addition to granite and basalt, the Earth's crust also contains other rock types such as sedimentary rocks (formed by the accumulation and compaction of sediments) and metamorphic rocks (formed from the transformation of existing rocks through heat and pressure). These rock types can be found in various regions of the Earth's crust, depending on geological processes and history.
It's important to note that the Earth's crust is just one layer of the Earth's structure. Below the crust lies the mantle, followed by the outer core and inner core. Together, these layers form the Earth's interior, each with distinct properties and compositions.