Basalt

Basalt is a dark, fine-grained volcanic rock formed when low-silica lava cools rapidly at or near Earth’s surface. It is the most common rock in Earth’s oceanic crust.

Igneous rock: Rock formed when molten material cools and solidifies. Basalt belongs to this broad class because it crystallizes from lava.
Lava: Molten rock that has erupted onto Earth’s surface. Basalt forms when low-silica lava cools and solidifies.
Mid-ocean ridge: A submarine mountain chain where tectonic plates separate and new oceanic crust forms. Basalt erupts along these ridges to create much of the ocean floor.
Andesite: A fine-grained volcanic rock with intermediate silica content between basalt and rhyolite. Andesite is generally richer in silica than basalt and common at subduction-zone volcanoes.
Basalt fiber: A manufactured fiber made by melting basalt rock and drawing the melt into fine filaments. It turns basalt’s mineral material into reinforcement for composite products.
Mafic rock: Igneous rock relatively rich in magnesium and iron and relatively low in silica. Basalt’s chemistry places it among mafic rocks.
Magma: Molten or partially molten rock beneath Earth’s surface, commonly containing dissolved gases and crystals. Basaltic magma supplies the lava that cools into basalt.
Deccan Traps: A vast region of layered flood basalts in western and central India. Its stacked basalt flows record an immense episode of volcanism.
Rhyolite: A silica-rich, fine-grained volcanic rock, often associated with viscous magma and explosive eruptions. Rhyolite contrasts with basalt in silica content, viscosity, and typical eruption style.
Basalt rebar: A composite reinforcing bar made from continuous basalt fibers bound in resin. It is used as a corrosion-resistant alternative to steel reinforcement in some structures.

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