Volcano definition

A cone-shaped hill or mountain, wholly or chiefly of volcanic materials, built up around the vent, usually so as to form a crater.

An opening in the Earth's crust from which lava, ash, and hot gases flow or are ejected during an eruption.

A high and low pressure disturbance cause the magma to rise to the surface and spill over the top.

The definition of a volcano is a rupture in the Earth's crust where molten lava, hot ash, and gases from below the Earth’s crust escape into the air.

Pressure builds in a volcano until the pressure must be expelled. The liquid and heat build up and force the lighter, melted rock buried deep below to the surface toward the surface of the Earth, causing an eruption.

A vent in the earth's crust through which molten rock (lava), rock fragments, gases, ashes, etc. are ejected from the earth's interior: a volcano is active while erupting, dormant during a long period of inactivity, or extinct when all activity has finally ceased.

The rock element of the magma is categorized as either Rhyolite, Andesite, or Basalt.

Plate Volcanoes - The majority of volcanoes are formed when two of the Earth’s plates meet and collide. These volcanoes actually occur on the ocean floor.

Caldera Volcanoes - Caldera volcanoes are formed from considerable amounts of magma erupting from sub-surface magma chambers. When the magma erupts, it leaves an empty space below the surface. The eruption of a caldera volcano generally has the coolest lava; but, they are the most dangerous because their eruption might also cause tsunamis, large pyroclastic surges, and widespread falling of ash.

Decade Volcanoes - These volcanoes are sixteen volcanoes that have been identified by scientists as noteworthy due to their large eruptions, and their closeness to populated areas. They include: Avachinsky-Koryaksky in Russia, Nevado de Colima in Mexico, Mount Etna in Italy, Galeras in Colombia, Mauna Loa in the United States, Mount Merapa in Indonesia, Mount Nyiragongo in Africa, Mount Rainer in the United States, Sakurajima in Japan, Santa Maria in Guatemala, Santorini in Greece, Taal Volcano in the Philippines, Teide in Spain, Ulawun in New Britain, Mount Unzen in Japan, and Mount Vesuvius in Italy.

Natural radioactive decay that occurs within the Earth causes a large amount of heat to be produced, which causes more rocks to melt into magma which travels towards the surface.

A usually cone-shaped mountain formed by the materials issuing from such an opening. Volcanoes are usually associated with plate boundaries but can also occur within the interior areas of a tectonic plate. Their shape is directly related to the type of magma that flows from them—the more viscous the magma, the steeper the sides of the volcano. &diamf3; A volcano composed of gently sloping sheets of basaltic lava from successive volcanic eruptions is called a shield volcano . The lava flows associated with shield volcanos, such as Mauna Loa, on Hawaii, are very fluid. &diamf3; A volcano composed of steep, alternating layers of lava and pyroclastic materials, including ash, is called a stratovolcano . Stratovolcanos are associated with relatively viscous lava and with explosive eruptions. They are the most common form of large continental volcanos. Mount Vesuvius, Mount Fuji, and Mount St. Helens are stratovolcanos.

Shield Volcanoes - Shield volcanoes are extremely broad and flat when compared to other volcanoes.

Composite Volcanoes - Composite volcanoes, also known as strato-volcanoes, are formed by alternate layers of rock fragments and lava. The shape of a composite volcano is large and cone-like.

Most eruptions occur when gas expands inside the Earth, reducing pressure and causing aggressive volcanic behavior.

Expelled magma on the surface of the Earth can take up to several hundred years to cool depending on its composition and location.

The molten lava that flows down the side of a volcano is composed of a mixture of gases, liquid rock, silica and crystals.

A major area of volcanic activity is called the "Ring of Fire" which extends around the Pacific Plate from Alaska down both sides of the Pacific Ocean, around Australia and down to the Antarctic continent.

A usually cone-shaped mountain formed from the materials issuing from such an opening.

An opening in the earth's crust from which lava, ash, and hot gases flow or are ejected during an eruption.

A similar opening on the surface of another planet.