GEOLOGY & PLANETARY SCIENCE A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site magma Sketch of a magma reservoir beneath a volcano and a conduit leading up to a lava dome at the surface. Arrow indicates direction of magma movement from a deeper source. Credit: B. Myers / U.S. Geological Survey Molten rock in the interior of the Earth (or some other planet or moon). If it reaches the surface it is known as lava; upon solidifying it forms igneous rock. Magma typically consists of (1) a liquid portion (often referred to as the melt); (2) a solid portion made of minerals that crystallized directly from the melt; (3) solid rocks incorporated into the magma from along the conduit or reservoir, called xenoliths or inclusions; and (4) dissolved gases. Magma that cools and solidifies within the crust may form either plutonic (at great depths) or hypabyssal (at intermediate depths) rocks. Related category    • GEOLOGY AND PLANETARY SCIENCE Source: U.S. Geological Survey Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP