Much like hot fudge being poured over cold ice cream, this transfer of heat is able to melt the surrounding rock (the “ice cream”) into magma. As the liquid rock solidifies, it loses its heat to the surrounding crust. Magma can also be created when hot, liquid rock intrudes into Earth’s cold crust. These volcanic mounds can grow into volcanic islands over millions of years of activity. When located beneath the ocean, these plumes, also known as hot spots, push magma onto the seafloor. The rock then cools into new crust.ĭecompression melting also occurs at mantle plumes, columns of hot rock that rise from Earth’s high-pressure core to its lower-pressure crust. The rifting movement causes the buoyant magma below to rise and fill the space of lower pressure. This reduction in overlying pressure, or decompression, enables the mantle rock to melt and form magma.ĭecompression melting often occurs at divergent boundaries, where tectonic plates separate. Areas of lower pressure always have a lower melting point than areas of high pressure. This hot material rises to an area of lower pressure through the process of convection. Most of the mantle and crust are solid, so the presence of magma is crucial to understanding the geology and morphology of the mantle.ĭifferences in temperature, pressure, and structural formations in the mantle and crust cause magma to form in different ways.ĭecompression melting involves the upward movement of Earth's mostly solid mantle. Magma originates in the lower part of Earth’s crust and in the upper portion of the mantle. The core is the superheated center, the mantle is the thick, middle layer, and the crust is the top layer on which we live. This heat makes magma a very fluid and dynamic substance, able to create new landforms and engage physical and chemical transformations in a variety of different environments.Įarth is divided into three general layers. Magma is extremely hot-between 700° and 1,300° Celsius (1,292° and 2,372° Fahrenheit). Magma that has cooled into a solid is called igneous rock. When magma is ejected by a volcano or other vent, the material is called lava. This mixture is usually made up of four parts: a hot liquid base, called the melt minerals crystallized by the melt solid rocks incorporated into the melt from the surrounding confines and dissolved gases. Magma is a molten and semi-molten rock mixture found under the surface of Earth.

High viscosity magma