Bassalt

Basalt is a common extrusive igneous (volcanic) rock formed from the rapid cooling of basaltic lava exposed at or very near the surface of a planet or moon. It is typically fine-grained due to the rapid cooling of the lava, with crystals too small to be seen without magnification. The chemical composition of basalt is characterized by its low silica content, generally between 45% and 52%. It is rich in magnesium and iron, which gives it its dark color, often black or dark gray.

Basalt is a fundamental component of oceanic crust, making up the vast majority of the seafloor. On continents, it often forms in areas of volcanic activity, such as rift valleys, oceanic plateaus, and large igneous provinces. Pillow basalt, a distinctive type of basalt, forms when lava erupts underwater. The rapid cooling in water causes the lava to solidify into rounded, pillow-like shapes.

The formation of basalt is a key process in plate tectonics. Volcanic activity at mid-ocean ridges generates new oceanic crust, and large-scale basaltic eruptions can cover vast areas of land, forming basalt plateaus. Its widespread occurrence and relative ease of formation make it one of the most abundant rock types on Earth. Basalt has various uses, including as an aggregate in construction, for making crushed stone, and in some decorative applications due to its durability and color.