Magma

In this part of the lesson we will know all about magma.

What is Magma?

Magma is a kind of mixture of molten or semi-molten rock, volatiles and solids. Besides, molten rock may contain suspended crystals and dissolved gases. It is often to collect in magma chambers that may feed a volcano or turn into a pluton. And it is capable of intrusion into adjacent rocks, giving rise to Sills and Dikes, and extrusion onto the surface as lava, and explosive ejection as Tephra to form pyroclastic rocks. The Tephra is all the volcanic material such as Ash, Plumes, Volcanic Bombs, Volcanic Blocks, lapilli etc.

There are four types of magma.

Ultramafic Magma

Ultramafic Magma also known as Picritic Magma is the hottest and fastest-flowing of the magmas, running almost as fast as water down a volcano. In the distant past. Its lava could reach as high as 1,600 degrees Celsius. Now lava rarely reaches above 1,200 degrees.

Basaltic Magma

Basaltic magma also known as Mafic magma is made up of 45 to 55 percent silica. It is high in iron, magnesium and calcium and is low in potassium and sodium. The temperature of basaltic magma is around 1,000 to 1,200 degrees Celsius, based on laboratory measurement and limited field operations. Basaltic magma is the most fluid of the four types of magma, though it is still 10,000 to 100,000 times less fluid than water. It also has the lowest amount of gas of the four types. Basalt magma is found at Earth's "hot spots," such as Hawaii.

Andesitic Magma

Andesitic magma is the "middle" magma in terms of heat; fluidity, or speed of flow; and gas content. It is probably 800 to 1,000 degrees Celsius. It is made up of 55 to 65 percent silica with average amounts of iron, magnesium, calcium, potassium and sodium. Andesitic magma is somewhat explosive, coming to the crust of the Earth at reverse fault areas. Small- to medium-sized earthquakes also release andesitic magma.

Felsic Magma

Felsic magma also known as Rhyolitic Magma. Includes ryolitic and dacite magmas, which are very thick and slow-moving. It seems to form when the Earth's crust melts with seawater. Felsic magma is made up of 65 to 75 percent silica. It is low in iron, magnesium and calcium and is high in potassium and sodium. Compared to other types of magma, felsic magma is cool, reaching 650 to 800 degrees Celsius, and is high in volatile, or unstable, gases and melted rocks. Felsic magma forms huge calderas, like the Yellowstone caldera.