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A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice, typically a volcanic cone or mountain. [2] [22]
A’a lava has a rough, spiny surface made of clasts of lava called clinkers. [16] Block lava is another type of lava, with less jagged fragments than in a’a lava. [17] Pahoehoe lava is by far the most common lava type, both on Earth and probably the other terrestrial planets. It has a smooth surface, with mounds, hollows and folds. [3]
Volcanologists frequently visit volcanoes, especially active ones, to observe volcanic eruptions, collect eruptive products including tephra (such as ash or pumice), rock and lava samples. One major focus of enquiry is the prediction of eruptions; there is currently no accurate way to do this, but predicting or forecasting eruptions, like ...
In 2009, a paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism. It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma, as defined for that body, and/or magmatic gas is erupted.' This article mainly covers volcanoes on Earth.
Volcanoes are usually mountains (sometimes islands, lakes, plateaus, calderas, seamounts or lava domes) that are formed when magma (liquid rock) wells up from inside the Earth. There are also analogous formations away from the Earth. Many volcanoes are categorized both as volcanoes and other landforms, such as mountains (if qualified).
Map of Earth's plate boundaries and active volcanoes More detailed map showing volcanoes active in the last 1 million years These lists cover volcanoes by type and by location. Type
The first English-language paper on the subject was published in 1947 by William Henry Mathews, describing the Tuya Butte field in northwest British Columbia, Canada. The eruptive process that builds these structures, originally inferred in the paper, [57] begins with volcanic growth below the glacier.
World map of active volcanoes and plate boundaries Kīlauea's lava entering the sea Lava flows at Holuhraun, Iceland, September 2014. An active volcano is a volcano that has erupted during the Holocene (the current geologic epoch that began approximately 11,700 years ago), is currently erupting, or has the potential to erupt in the future. [1]