What makes magma move

The remaining elements make up the other one-quarter. Magmas derived from crustal material are dominated by oxygen, silicon, aluminum, sodium, and potassium. The composition of magma depends on the rock it was formed from by melting , and the conditions of that melting. Magmas derived from the mantle have higher levels of iron, magnesium, and calcium, but they are still likely to be dominated by oxygen and silicon.

All magmas have varying proportions of elements such as hydrogen, carbon, and sulphur, which are converted into gases like water vapour, carbon dioxide, and hydrogen sulphide as the magma cools. Virtually all of the igneous rocks that we see on Earth are derived from magmas that formed from partial melting of existing rock, either in the upper mantle or the crust.

Partial melting is what happens when only some parts of a rock melt; it takes place because rocks are not pure materials. Most rocks are made up of several minerals, each of which has a different melting temperature.

The wax in a candle is a pure material. If instead you took a mixture of wax, plastic, aluminum, and glass and put it into the same warm oven, the wax would soon start to melt, but the plastic, aluminum, and glass would not melt Figure 3. Again this is partial melting. As you can see from Figure 3. It is most likely that this is a very fine-grained mixture of solid wax and solid plastic, but it could also be some other substance that has formed from the combination of the two.

The high pressure changes the rock into a viscous semisolid called magma. This semisolid magma continues to move upwards through the crust, experiences less pressure and so becomes more fluid. 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 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.

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The Rock Cycle. View Collection. Earth Structure. View Article. Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. According to the United States Geologic Survey, there are approximately 1, potentially active volcanoes worldwide. Most are located around the Pacific Ocean in what is commonly called the Ring of Fire.

A volcano is defined as an opening in the Earth's crust through which lava, ash, and gases erupt. The term also includes the cone-shaped landform built by repeated eruptions over time.

Teach your students about volcanoes with this collection of engaging material. Magma is a mixture of molten and semi-molten rock found beneath the surface of the Earth. Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image lava flow Lava magma that has erupted onto the Earth's surface is visually mesmerizing — as the molten rock flows downhill, lava exposed to the air cools to a deep black color, while the molten rock beneath glows bright orange.

Photograph by Budkov Denis.