Basaltits

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 a microscope. The texture of basalt is generally aphanitic or phaneritic. Basalt is the most common volcanic rock on Earth, found on the ocean floor, in large igneous provinces, and on other terrestrial planets.

The composition of basalt is dominated by plagioclase feldspar and pyroxene minerals. Olivine is also a common accessory mineral. The color of basalt is typically dark gray to black, due to the high iron and magnesium content. However, weathered basalt can appear reddish-brown or even greenish due to oxidation of iron minerals.

Basaltic lava flows are characteristic of shield volcanoes and flood basalts. These eruptions can produce vast plains of solidified lava. Columnar jointing is a common feature of basaltic lava flows that cool slowly and contract. This results in the formation of hexagonal or polygonal columns.

Basalt plays a significant role in Earth's geology. The oceanic crust is primarily composed of basalt. Large igneous provinces, which are vast outpourings of basaltic lava, have had major impacts on Earth's climate and biosphere throughout geological history. Basalt is also found on the Moon, where it forms the dark plains known as lunar maria.