Basement rock

Basement rock refers to the thick foundation of ancient, and oldest, metamorphic rock and igneous rock that forms the crust of continents, often in the form of granite. Basement rock is contrasted to overlying sedimentary rock which is laid down on top of the basement rock after the continent was formed, the sedimentary rock often being relatively young and thin.

Formation

Basement rock primarily consists of two types of rocks: igneous rock and metamorphic rock. Igneous rock forms from the cooling and solidification of magma or lava. This process can occur either at the surface of the Earth, resulting in volcanic rock, or beneath the surface, resulting in plutonic rock. Metamorphic rock, on the other hand, forms from the transformation of existing rock types through heat, pressure, or chemical processes, without the rock melting into liquid magma.

Characteristics

Basement rock is typically high-grade, meaning it has been subjected to heat and pressure, and often reworked by tectonic forces; it is commonly more resistant to weathering than the overlaying rock. This resistance to weathering means that basement rock often forms the mountain peaks and ridges in mountainous areas.

Distribution

Basement rock is found throughout the world, underlying the majority of continental landmasses. It is often covered by younger sedimentary rock, but can be exposed at the surface in areas of mountain building, or where erosion has removed the overlying sedimentary rock.

Importance

Basement rock plays a crucial role in the geology of continents. It provides a record of the early history of continents, including information about the processes of continental formation and the geological events that occurred on the continent. In addition, basement rock can influence the distribution of mineral resources, as certain types of mineral deposits are associated with specific types of basement rock.