The magma in a magma chamber usually exists in several layers, based upon the density of the materials composing the lava. The least-dense magma rises to the top, while the denser magma settles toward the bottom of the magma chamber.
Full Definition of ACCRETION. 1. : the process of growth or enlargement by a gradual buildup: as a: increase by external addition or accumulation (as by adhesion of external parts or particles) b: the increase of land by the action of natural forces. 2. â acÂ·creÂ·tionÂ·ary \-shÉ-Ëner-Ä, -Ëne-rÄ\ adjective.
Accretion disks are common around smaller stars, or stellar remnants in a close binary, or black holes surrounded by material, such as those at the centers of galaxies. Some dynamics in the disk, such as dynamical friction, are necessary to allow orbiting gas to lose angular momentum and fall onto the central