The eruptive products of volcanoes typically contain liquids, crystals, and insoluble gases that have never before reached the Earth’s surface.
What is Magma?
“Magma” refers to “molten rock, typically found within magma chambers close to the Earth’s surface.” Magma is a mixture of liquid silicates at high temperature and pressure, and it is the original source of all types of igneous rocks. It has the ability to intrude into adjacent rock layers or erupt onto the surface.
Magma exists at temperatures ranging from 650 to 1,200°C. It is subjected to high pressure underground and, when it erupts to the surface through volcanic vents, it manifests as lava and pyroclastic materials. The eruptive products of volcanoes typically contain liquids, crystals, and insoluble gases that have never before reached the Earth’s surface.
Magma exists at temperatures ranging from 650 to 1,200°C.
Magma is concentrated in numerous separate magma chambers within the Earth’s crust and can vary significantly in composition across different regions. It can be found in subduction zones, fault lines, mid-ocean ridges, or hotspots containing plumes of molten rock from the mantle.
Formation of Magma
The formation of magma can only occur under specific conditions in the Earth’s asthenosphere. Magma can also be formed by the addition of volatile substances into heated rocks.
Volatiles are released from subducting oceanic plates. These substances infiltrate the overlying rock layers and stimulate melting. They can break the mineral bonds within the molten rock and lower the melting temperature, resulting in the formation of magma.
The formation of magma can also result from the melting of crustal rocks by previously existing magma. This magma, being at a higher temperature, can melt the surrounding crustal rock as it rises, leading to the generation of even more magma.
Magma signals an impending volcanic eruption.
Composition of Magma
The composition of magma varies depending on the makeup of the rocks being melted when the magma intrudes into the Earth’s crust and is expelled in the form of lava. There are three basic types of magma: mafic, andesitic, and felsic.
Magma is primarily a mixture of silica, alkalis, and alkaline earths (sodium, potassium, calcium, magnesium) and iron. Generally, the more mafic the magma, the smoother the eruption tends to be. This is because high silica content can lead to the accumulation of volatiles, which may result in explosive eruptions commonly observed in complex volcanoes.
