Magma 101

Magma: Formation, Composition, and Characteristics

• Magma is liquid rock found beneath the surface of the Earth, primarily within the crust and upper mantle.
• Magma consists of a combination of liquid, solid, and semi-liquid substances, as not all minerals and elements within it have the same melting point.
• The viscosity of magma varies depending on its type, with some being more viscous and others flowing more easily.
• Magma is found in zones below crustal features such as mid-ocean ridges, subduction zones, rift valleys, and hot spot volcanoes, where it can accumulate in magma chambers.
• The temperature of magma below these surface features ranges from 490 to 1600 degrees Celsius, with the Earth's core being the hottest at 5,430 degrees Celsius.
• Magma forms through geophysical processes such as mantle plumes and convection currents, as well as through the subduction of plate material colliding with another.
• Mantle plumes originate at the boundary between the outer core and lower mantle, gradually rising to the base of the lithosphere, where they spread out and can melt rock due to the decrease in pressure.
• Magma created in upper mantle plumes can accumulate in large magma chambers and form hot spot volcanoes, while magma from convection currents can contribute to the formation of oceanic crust at mid-ocean ridges and rifts.
• Magma is also formed at subduction zones, where the increasing temperature and the presence of water cause the subducted plate material to melt, forming magma.
• The composition of magma varies depending on its formation, with magmas from mantle plumes having higher iron and magnesium concentrations, while felsic magma, with a high silica content, tends to be extremely viscous and adhesive.
• Felsic magma typically ranges in temperatures from 800 to 1,200 degrees Celsius, and is relatively low in iron content.
• Magma consists of different compounds and elements with varying melting points, leading to variations in its composition.