How is molten formed

The layers of magma may be document ed by the type of eruption material the volcano emits. Gases, ash, and light-colored rock are emitted first, from the least-dense, top layer of the magma chamber. Dark, dense volcanic rock from the lower part of the magma chamber may be released later. In violent eruptions, the volume of magma shrinks so much that the entire magma chamber collapses and forms a caldera.

All magma contains gases and a mixture of simple element s. Being that oxygen and silicon are the most abundant elements in magma, geologists define magma types in terms of their silica content, expressed as SiO 2. These differences in chemical composition are directly related to differences in gas content, temperature, and viscosity.

This type of magma has a low gas content and low viscosity, or resistance to flow. Mafic magma also has high mean temperatures, between o and o Celsius o and o Fahrenheit , which contributes to its lower viscosity. Low viscosity means that mafic magma is the most fluid of magma types.

This lava cools into basalt , a rock that is heavy and dark in color due to its higher iron and magnesium levels. The Hawaiian Islands are a direct result of mafic magma eruptions. This results in a higher gas content and viscosity. Its mean temperature ranges from o to o Celsius o to o Fahrenheit. This more gaseous and sticky lava tends to explode violently and cools as andesite rock. Intermediate magma most commonly transforms into andesite due to the transfer of heat at convergent plate boundaries.

Andesitic rocks are often found at continent al volcanic arcs, such as the Andes Mountains in South America, after which they are named. As a result, felsic magma also has the highest gas content and viscosity, and lowest mean temperatures, between o and o Celsius o and o Fahrenheit. These trapped bubbles can cause explosive and destructive eruptions. These eruptions eject lava violently into the air, which cools into dacite and rhyolite rock.

Much like intermediate magma, felsic magma may be most commonly found at convergent plate boundaries where transfer of heat and flux melting create large stratovolcano es. Magma exists as pockets and plumes beneath the surface of the Earth. Photograph by Carsten Peter, National Geographic. Mysterious Magma. Magma is usually studied as lava or igneous rock. In , the Icelandic Deep Drilling Project created a well that uses magma to generate geothermal energy.

Normally, geothermal energy is created by pumping water into hot volcanic bedrock, creating steam that is then harnessed to generate electricity. This huge increase in temperature allowed just one magma well to generate roughly 36 megawatts of electricity, powering 36, homes.

In comparison, one single wind turbine generates between 1 to 3 megawatts. Also called a collision zone. Also called the average. Also known as a composite volcano. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Media If a media asset is downloadable, a download button appears in the corner of the media viewer. Larger fragments fall back around the vent, and accumulations of fall-back fragments may move downslope as ash flows under the force of gravity.

Some of the finer ejected materiaIs may be carried by the wind only to fall to the ground many miles away. The finest ash particles may be injected miles into the atmosphere and carried many times around the world by stratospheric winds before settling out.

Fountaining lava and volcanic debris during the Kilauea Iki eruption of Kilauea Volcano, Hawaii. M olten rock below the surface of the Earth that rises in volcanic vents is known as magma , but after it erupts from a volcano it is called lava.

Originating many tens of miles beneath the ground, the ascending magma commonly contains some crystals, fragments of surrounding unmelted rocks, and dissolved gases, but it is primarily a liquid composed principally of oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese. Magmas also contain many other chemical elements in trace quantities.

Upon cooling, the liquid magma may precipitate crystals of various minerals until solidification is complete to form an igneous or magmatic rock.

T he diagram below shows that heat concentrated in the Earth's upper mantle raises temperatures sufficiently to melt the rock locally by fusing the materials with the lowest melting temperatures, resulting in small, isolated blobs of magma. These blobs then collect, rise through conduits and fractures, and some ultimately may re-collect in larger pockets or reservoirs "holding tanks" a few miles beneath the Earth's surface. Get News Updates by Email. Connect with us online NSF website: nsf.

Follow us on social Twitter: twitter. NSF Instagram: instagram. Contact Help Search search. Search search. Home News. Email Print Share. Credit and Larger Version Peridotite is a pale green olive-colored rock derived from Earth's mantle. Credit and Larger Version Microscopic sample of rock in a high-pressure lab; it shows evidence of magma formation. Credit and Larger Version Geologist Rajdeep Dasgupta uses hydraulic presses to crush rocks at high pressures.

The result is the lava we see erupting from active volcanoes. Only in certain areas where the crust is fractured or broken called fissures — like at the edge of a tectonic plate boundary — can the molten mantle start to creep through. The rock in the mantle is less dense than the crust that contains it so it will rise through any gaps. The molten magma is also hotter than the surrounding crust so it will begin to melt some of the solid rocks that surround it.

The edges of tectonic plates form an ideal location for volcanoes to form. This becomes a ready supply of new molten magma, which can result in more volcanoes. Learn more about this in the article Plate tectonics, volcanoes and earthquakes.