Basalt It is a generic term that applies to dark igneous rocks composed of minerals that are relatively rich in iron (Fe) and magnesium (Mg). They are common in volcanic areas.
Basalt is the most common variety of volcanic rock. It is formed by the effusion of lava along the oceanic mountain ranges, where the seabed, extending, adds new crust to counteract losses by subduction.
It is usually dark gray, and often has a vesicular texture that preserves the vestiges of bubbles produced by expanding water vapor, generated during the cooling and solidification of lava.
Basalt masses are also padded, caused by the rapid cooling of lava emitted after an eruption on the seabed.
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