page_title: Caldera
section_title: Toba
hierarchical_section_title: Caldera / Types of caldera / Explosive caldera eruptions / Toba
caption_attribution_description: English: La Cumbre volcano, Fernandina Island, Galapagos. Photographed from the International Space Station. ISS Crew Earth Observations: ISS005-E-6997 Identification Mission ISS005 (Expedition 5) Roll E Frame 6997 Country or Geographic Name GALAPAGOS ISLANDS Features LA CUMBRE VOLCANO, FERNANDINA Center Point Latitude -0.5° N Center Point Longitude -91.5° E Camera Camera Tilt 40° Camera Focal Length 800&#160;mm Camera Kodak DCS760C Electronic Still Camera Film 3060 x 2036 pixel CCD, RGBG array. Quality Percentage of Cloud Cover 0-10% Nadir What is Nadir? Date 2002-07-06 Time 20:21:02 Nadir Point Latitude -2.9° N Nadir Point Longitude -93.3° E Nadir to Photo Center Direction Northeast Sun Azimuth 312° Spacecraft Altitude 214 nautical miles (396&#160;km) Sun Elevation Angle 51° Orbit Number 713 Original image caption La Cumbre volcano on Fernandina Island is the most active volcano on the Galapagos, erupting most recently in 1995. The volcano rises 1495 m from sea level. This photo was taken by the Expedition 5 crew aboard the International Space Station. The scene provides a detailed view of the 850-m-deep summit caldera. The dark flows in the middle of the caldera floor were erupted in 1991. Today, these flows are partly covered by dark green vegetation.
context_page_description: A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber/reservoir in a volcanic eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost. The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven caldera-forming collapses are known to have occurred since 1900, most recently at Bárðarbunga volcano, Iceland in 2014.
context_section_description: About 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres (670 cu mi) dense-rock equivalent of ejecta. This was the largest known eruption during the ongoing Quaternary period (the last 2.6 million years) and the largest known explosive eruption during the last 25 million years. In the late 1990s, anthropologist Stanley Ambrose proposed that a volcanic winter induced by this eruption reduced the human population to about 2,000–20,000 individuals, resulting in a population bottleneck. More recently, Lynn Jorde and Henry Harpending proposed that the human species was reduced to approximately 5,000-10,000 people. There is no direct evidence, however, that either theory is correct, and there is no evidence for any other animal decline or extinction, even in environmentally sensitive species. There is evidence that human habitation continued in India after the eruption.
  Eruptions forming even larger calderas are known, especially La Garita Caldera in the San Juan Mountains of Colorado, where the 5,000 cubic kilometres (1,200 cu mi) Fish Canyon Tuff was blasted out in eruptions about 27.8 million years ago.
  At some points in geological 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 (formed during the Oligocene, Miocene, and Pliocene epochs) or the Saint Francois Mountain Range of Missouri (erupted during the Proterozoic eon).
caption: Satellite photograph of the summit caldera on Fernandina Island in the Galápagos archipelago.
exif: {}