Volcanoes biography

What is a volcano?

Many mountains form by folding, faulting, uplift, and erosion of the Earth's crust. Volcanic terrain, however, is built by the slow accumulation of erupted lava. The vent may be visible as a small bowl shaped depression at the summit of a cone or shield-shaped mountain. Through a series of cracks within and beneath the volcano, the vent connects to one or more linked storage areas of molten or partially molten rock (magma). This connection to fresh magma allows the volcano to erupt over and over again in the same location. In this way, the volcano grows ever larger, until it is no longer stable. Pieces of the volcano collapse as rock falls or as landslides.

How do volcanoes erupt?

Molten 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. Magma is made of molten rock, crystals, and dissolved gas—imagine an unopened bottle of soda with grains of sand inside. The molten rock is made of the chemicals oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese. After cooling, liquid magma may form crystals of various minerals until it becomes completely solid and forms an igneous or magmatic rock.

Originating many tens of miles beneath the ground, magma is lighter than surrounding solid rock. It is driven towards Earth's surface by buoyancy, it is lighter than the surrounding rock, and by pressure from gas within it. Magma forces its way upward and may ultimately break though weak areas in the Earth's crust. If so, an eruption begins.

Magma can be erupted in a variety of ways. Sometimes molten rock simply pours from the vent as fluid lava flows. It can also shoot violently into the air as dense clouds of rock shards (tephra) and gas. Larger fragments fall back around the vent, and clouds of tep

A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes resulting from divergent tectonic activity are usually non-explosive whereas those resulting from convergent tectonic activity cause violent eruptions. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift, the Wells Gray-Clearwater volcanic field, and the Rio Grande rift in North America. Volcanism away from plate boundaries most likely arises from upwelling diapirs from the core–mantle boundary called mantle plumes, 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism or intraplate volcanism, in which the plume may cause thinning of the crust and result in a volcanic island chain due to the continuous movement of the tectonic plate, of which the Hawaiian hotspot is an example. Volcanoes are usually not created at transform tectonic boundaries where two tectonic plates slide past one another.

Volcanoes, based on their frequency of eruption or volcanism, can be defined as either active, dormant or extinct. Active volcanoes have a recent history of volcanism and are likely to erupt again, dormant ones have not erupted in a long time but may erupt later, while extinct ones are not capable of eruption at all. These categories aren't entirely uniform; they may overlap for certain examples.

Large eruptions can affect atmospheric temperature as ash

What are volcanoes, and why do they exist?

Volcanoes are places on the Earth’s surface where molten material (magma) can erupt. This definition will work on other planets and moons — even the icy moons of the outer solar system, where the ‘magma’ may be a chilly mixture of water ice, methane and ammonia. On Earth, most volcanoes erupt magma that is rich in silica, and that solidifies to form rock, like pumice or lava.

Volcanoes are a part of the Earth’s internal cooling system. The inside of the Earth is hot, and gets hotter with depth. In some places, between about 50 and 150 km deep, the rocky interior is hot enough to melt, forming droplets of magma that will then percolate up to the surface. Often, this magma also contains dissolved gases — like water (steam), carbon dioxide and sulphur — that leak out of the magma near the surface; or bubble out violently, causing an eruption. Over geological timescales this escape of hot magma from within leads to the slow cooling of the planet.

But not all volcanoes are created equal, right?

As a volcanologist, it is easy to revel in the differences between volcanoes: they all look different, and come in a spectrum of shapes and sizes. While this diversity may reflect underlying differences in the particular geological setting (where the magma is from, how old or thick the crust is, and the history of growth, and weathering), in the end all volcanoes are formed by the same sorts of processes.

Some of the most remarkable volcanoes that I have been lucky enough to visit include the Greek island of Santorini, with its spectacular flooded crater, and its vast multi-coloured cliffs that reveal its hyperactive past; and the mysterious Tanzanian volcano, Ol Doinyo Lengai, with its chocolate-coloured lava flows of molten washing soda. Then of course, there are the remarkable volcanoes I haven’t yet managed to visit: Paricutin, the cone that grew in a Mexican farmer’s cornfield; or any of th

Rupture in a planet's crust where material escapes

"Volcanic" redirects here. For other uses, see Volcano (disambiguation) and Volcanic (disambiguation).

A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes resulting from divergent tectonic activity are usually non-explosive whereas those resulting from convergent tectonic activity cause violent eruptions. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift, the Wells Gray-Clearwater volcanic field, and the Rio Grande rift in North America. Volcanism away from plate boundaries most likely arises from upwelling diapirs from the core–mantle boundary called mantle plumes, 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism or intraplate volcanism, in which the plume may cause thinning of the crust and result in a volcanic island chain due to the continuous movement of the tectonic plate, of which the Hawaiian hotspot is an example. Volcanoes are usually not created at transform tectonic boundaries where two tectonic plates slide past one another.

Volcanoes, based on their frequency of eruption or volcanism, can be defined as either active, dormant or extinct. Active volcanoes have a recent history of volcanism and are likely to erupt again, dormant ones have not erupted in a long time but may erupt later, wh