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The word basalt comes from a Latin word meaning very hard stone.
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Though basalt is typically a dark, black rock, weathering can lead to a yellow-brown color.
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Basalt may also be found in various shades because of geochemical processes.
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A light-color basalt is rare, but can be found due to a high concentration of plagioclase and weathering.
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Basalt is also an abundant rock found on the Moon with much of its surface underlain by basaltic lava flows and flood basalts as well, with the areas known as "lunar maria."
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Resurfacing of the Moon in large areas has taken place due to extensive basaltic flows which may have been triggered by major impact events. The ages of the areas can be measured by observing the density of impact craters. Older flows will have more craters.
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Olympus mons, a shield volcano on Mars, was formed from basaltic lava flows. It is the largest known volcano in the solar system and the highest mountain on Mars.
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Three rock-forming environments is responsible for most of the basalt formed on Earth: oceanic divergent boundaries, oceanic hotspots, and mantle plumes and hotspots beneath continents.
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Most basalt is formed by the divergent plate boundaries on the mid-ocean ridge system. Convection currents deliver hot rock from deep in the mantle, which melts as this boundary pulls apart, and the molten rock erupts onto the floor of the ocean.
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Significant amounts of basalt are produced in above-ocean hotspots. At these locations a small plume of rock rises up through the mantle from a hotspot on Earth's core. The Hawaiian Islands are an example of these basaltic volcanoes.
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Production of basalt at these island locations begins with an eruption on the ocean floor. A sustained hotspot and repeated eruptions results in a larger and larger volcanic cone leading to an island.
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The island of "Hawaii", is between 300,000 and 600.000 years old and began as an eruption on the floor of the Pacific Ocean. The cone grew following many eruptions and layer after layer of basalt flows.
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There are also Colorado River Flood Basalts, which are an extensive sequence of layers of lava flow reaching a thickness of up to 6,000 feet.
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A continental environment is where a mantle plume or hotspot delivers large amounts of basaltic lava through the continental crust and up to the Earth's surface. Eruptions can occur over millions of years producing layers of basalt vertically.
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Examples of other flood basalts include those in Washington, Oregon, and Idaho; the Emeishan Traps of China, the Deccan traps of India, and several others.
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Basalt is used to create cobblestone, by artists to create statues, for groundwork construction, and for building blocks.
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