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Basalt is the most abundant of the Earth's volcanic rocks. Basalt magma is believed to be formed by partial melting of mantle rocks near the base of the crust (tholeiites) and deeper in the mantle (olivine basalts).Most basalts occur in Lava flows and sheets; coarser grained basalts occur in Dikes. Basalt is a Igneous Rock. A basalt rock is dark, dense, and hard, and usually has a texture so fine-grained that individual crystals can be seen only under a microscope. Natural glass is common in the matrix. Basalts are made up of silicates such as plagioclase and pyroxene. Basalt contains small amounts of other minerals, including: MAGNETITE, and also ILLEMENITE, and many more. Basalts of sub oceanic origin may contain abundant OLIVINE. And it is also rhyolite and andesite. Basalt is found throughout the world. Most of the lava that pour out of volcanoes that make up oceanic islands are basaltic. For example, the great shieldlike volcano of Mauna Loa, in Hawaii, is made up of basaltic lava flows. Basalt plateaus of similar size occur in India and Brazil. Many modern volcanoes, such as Hekla in Iceland and Mount Etna in Italy, also erupt basaltic lava. On the contents, large volumes of food basalts made up such regions as the Columbia River and Snake River plateaus. Basalts also cover the dark low-lands of the moon, which are called Maria. Basaltic lava is extremely fluid and may flow long distances from its eruption site. When basalt erupts underwater, it forms rounded pillow shaped lumps called pillow lava. When it erupts on land, its surface has either a smooth, ropelike texture, or a jagged angular one. Sometimes as basaltic lava cools, it splits into four-five-, or six sided colums, such as those along the Columbia River in Washington.
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