![]() ![]() In areas where temperature, pressure, and structural formation allow, magma can collect in magma chambers. As it falls to Earth, tephra includes rocks such as pumice. In the atmosphere, tephra is more often called volcanic ash. This magma solidifies in the air to form volcanic rock called tephra. Magma can also extrude into Earth’s atmosphere as part of a violent volcanic explosion. Lava cools to form volcanic rock as well as volcanic glass. Lava eruptions can be “fire fountains” of liquid rock or thick, slow-moving rivers of molten material. ![]() The most familiar way for magma to escape, or extrude, to Earth’s surface is through lava. Many xenoliths are crystals torn from inside the Earth and embedded in magma while the magma was cooling. A xenolith is a piece of rock trapped in another type of rock. A magmatic dike is simply a large slab of magmatic material that has intruded into another rock body. A pluton is an intrusion of magma that wells up from below the surface. When it cools to solid rock, this intrusion is often called a pluton. Magma can intrude into a low-density area of another geologic formation, such as a sedimentary rock structure. An extrusion could include lava and volcanic rock. An intrusion can form features such as dikes and xenoliths. Magma leaves the confines of the upper mantle and crust in two major ways: as an intrusion or as an extrusion. In this case, water overlying the subducting seafloor would lower the melting temperature of the mantle, generating magma that rises to the surface. Much like heat transfer, flux melting also occurs around subduction zones. This creates magma in places where it originally maintained a solid structure. These compounds cause the rock to melt at lower temperatures. Over millions of years, the magma in this subduction zone can create a series of active volcanoes known as a volcanic arc.įlux melting occurs when water or carbon dioxide are added to rock. This process transfers heat and creates magma. As the denser tectonic plate subducts, or sinks below, or the less-dense tectonic plate, hot rock from below can intrude into the cooler plate above. Transfer of heat often happens at convergent boundaries, where tectonic plates are crashing together. 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. ![]()
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