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Click here to return to the Earth Systems Revision PageTypes of Magma Magma varies in its charcteristics (e.g. temperature, viscosity etc.), depending on the source of the magma / its location. The magma type is important in determining the nature of a volcanic eruption and the subsequent volcanic landforms that are produced (see section on characteristics and formation of extrusive landforms). | Basaltic Lava (Mafic) | Andesitic Lava (Intermediate) | Where Found? | Mid-Ocean Ridges | Subduction Zone | Silica Content? | Low silica content (~50%) | High silica content (~60%) | Viscosity? | Low viscosity, very hot and runny | Viscous, flows slowly | Temperature? | About 1200 oC | About 800 oC | Distance Travelled? | Long distance (cools slowly) | Short distance (cools quickly) | Frequency of Eruption? | Frequent, gentle eruptions | Less frequent, violent eruptions (gases build up) | Products erupted? | Lava and Steam | Ash, Rock, Gas, Steam and Lava |
The most explosive magma type is known as Rhyolitic (felsic) which is very high in silica (above 75%) and highly viscous. See the following links / resources... A good article on the characteristics of magma Also see this interesting overview on how the charactersitics of magma may affect the type of eruption in terms of its explosiveness (quite detailed - but also includes the basics) Brief but succinct online summary comparison table of magma types (pdf file - will require adobe acrobat reader) - please be aware that although we haven't looked at it as such - rhyoltic magma is the most explosive magma due to its high silica content and high viscosity |
