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's caldera, formed in the A caldera is a Volcanic feature formed by the collapse of land following a volcanic eruption. They are often confused with Volcanic Crater s. The word 'caldera' comes from the Spanish Language , meaning " Cauldron ". CALDERA FORMATION A collapse is triggered by the emptying of the Magma Chamber beneath the volcano, usually as the result of a large Volcanic Eruption . If enough magma is erupted, the emptied chamber will not be able to support the weight of the ''volcanic edifice'' (the Mountain ) above. Fractures will form around the edge of the chamber, usually in a roughly circular shape. These ''ring fractures'' may in fact serve as volcanic vents. As the magma chamber empties, the center of the volcano within the ring fractures begins to collapse. The collapse may occur as the result of a single massive eruption, or it may occur in stages as the result of a series of eruptions. The total area that collapses may be hundreds or thousands of square kilometers. image of Lake Toba . A Resurgent Dome formed the island of Samosir .]] Explosive calderas If the magma is rich in Silica , the caldera is often filled in with Ignimbrite , Tuff , Rhyolite , and other Igneous Rock s. Silica-rich magma is very Viscous . As a result, gases tend to become trapped at high pressure within the magma. When the magma gets near the surface of the Earth, the gas expands quickly, causing Explosion s and spreading Volcanic Ash over wide areas. Further Lava flows may be erupted, and the center of the caldera is often uplifted in the form of a '' Resurgent Dome '' by subsequent intrusion of magma. A ''silicic'' or ''rhyolitic caldera'' may erupt hundreds or even thousands of Cubic Kilometer s of material in a single event. Even small caldera-forming eruptions, such as Krakatoa in 1883 or Mount Pinatubo in 1991, may result in significant local destruction and a noticeable drop in temperature around the world. Large calderas may have even greater effects. When induced by this eruption reduced the Human population to a few thousand individuals, resulting in a Population Bottleneck (''see'' Toba Catastrophe Theory ). Even larger caldera-forming eruptions are known, especially La Garita Caldera in the San Juan Mountains of Colorado , where the 5,000 cubic kilometer Fish Canyon Tuff was blasted out in a truly major single eruption 27.8 million years ago. At some points in Geologic Time , rhyolitic calderas have appeared in distinct clusters. The remnants of such clusters may be found in places such as the San Juan Mountains of Colorado (erupted during the Tertiary Period ) or the Saint Francois Mountain Range of Missouri (erupted during the Proterozoic ). 's summit caldera]] Non-explosive calderas Some volcanoes, such as Caldera has an inner crater known as Halema‘uma‘u, which has often been filled by a lava lake. The largest volcano on Earth, Mauna Loa is also capped by a subsidence caldera called Moku‘āweoweo Caldera. Non-volcanic calderas It is possible, although rare, for a caldera-like formation to be created by erosion rather than volcanism. It is believed that the Caldera De Taburiente on La Palma in the Canary Islands is an example of this. NOTABLE CALDERAS ''See also
, Oregon, formed around 5,680 BCE]] , Idaho easily recognized from space. Yellowstone Park to east, Teton Range to southwest.]]
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SEE ALSO EXTERNAL LINKS
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