Types Of Volcano

Stratovolcanoes
Some stratovolcanoes may form in a few thousand years, but may remain active for tens to hundreds of thousands of years. During their lifespans, dormant intervals may also last tens of thousands of years. Perhaps the most common rock type of stratovolcanoes is andesite (named after the Andes Mountains), but stratovolcanoes form in a wide variety of tectonic settings and erupt a wide range of rocks. Their steep-sided profiles are often exaggerated even further by artists for dramatic effect. [Read more]

Shield Volcanoes
Their name derives from their low-angle profile, which resembles the broad shields used by Hawaiian warriors. They are formed primarily by the successive accumulation of fluid lava flows, which descend from summit or flank fissure systems. Although shield volcanoes are not as visually dramatic as stratovolcanoes, they are often much larger features. Oceanic shield volcanoes such as those in the Hawaiian Islands can rise as much as 8000 m above the surrounding sea floor and 12,000 m above their actual bases, which have sagged due to the immense mass of the volcano.
[Read more]

Calderas
Calderas are large volcanic depressions formed by collapse of the summit or flanks of a volcano into underlying chambers evacuated by very large explosive eruptions or the effusion of large volumes of lava flows. Earth's calderas range from a kilometer to as much as about 100 kilometers in width; many contain scenic caldera lakes. Calderas may be simple structures formed during an eruption that truncates either the summit of a single stratovolcano or a complex of multiple overlapping volcanoes,
[Read more]

Craters
Craters differ from calderas both in size and origin. Craters are much smaller features than calderas and are typically defined as being less than 1 km in diameter. Although both craters and calderas are most often associated with explosive eruptions, craters are typically formed by the explosive ejection of material in and surrounding the upper part of the conduit, rather than by collapse. Steep-walled pit craters, in contrast, often found on shield volcanoes, are more passive features formed when magma drains from a fissure, leaving overlying lava flow.....
[Read more]

Fissure Vents
Fissures often extend radially away from the summit and can reach from the upper part of the volcano to its base. Fissures can also reflect regional tectonic trends independent of the volcanoes themselves, such as in Iceland, where the mid-Atlantic Ridge rises above sea level, or along continental rift zones such as those in eastern Africa. Volcanoes in the Galápagos Islands are notable for circumferential fissures that parallel the rims of large summit calderas. Although explosive eruptions and lava effusion can occur simultaneously over long portions of a fissure, activity often migrates along a fissure and is subsequently localized at a few specific points, where cones or craters can form.
[Read more]

Pyroclastic Cones
Pyroclastic cones typically range from a few tens of meters to a few hundred meters in height and are most often formed during single eruptions, when explosively ejected material accumulates around the vent. The slopes of pyroclastic cones consequently approach the angle of repose of its constituent materials. Pyroclastic cones, also known as cinder cones or scoria cones, can form rapidly, but remain active for long periods of time.
[Read more]

Lava Domes
Lava domes are formed when viscous magma slowly extrudes from a vent and piles up around it. Silicon promotes rigidity in magmas because it has a +4 charge and forms multiple bonds with other elements. Domes are consequently often produced by magmas of more silica-rich dacitic-to-rhyolitic compositions. Domes are steep-sided structures typically a few tens of meters to a few hundred meters high and can form at the summit of a volcano, on its flanks, or as independent volcanic centers.
[Read more]