What is magma and how does it form igneous rock?
Magma is a hot liquid mixture formed by partial melting of rock by Earth’s natural heat sources. In addition to a silicate (rich in silicon and oxygen) liquid which contains molecules and other structures which will form silicate minerals upon cooling, magma contains ions of common elements, dissolved gases, separated gas bubbles, and some inherited or early crystallizing mineral grains. A common magma in oceanic regions forms volcanic lava flows of basalt, a dark, fine grained rock which has cooled rapidly by eruption on Earth’s surface. A second type of common magma invades the crust below mountain regions and cools slowly to form coarse grained, light colored granite. Igneous eruptions and intrusions are evidence of internal heat production and in fact, cool Earth.
