Of the 1,511 volcanoes known to have erupted in the past 10,000 yr, 164 are shield volcanoes. Vent. A shield volcano is the largest kind of volcano that erupts a thin, low-viscosity, basaltic lava gently and over a large area. [11] Shield volcanoes are similar in origin to vast lava plateaus and flood basalts present in various parts of the world. The composition of the lavas of the Galápagos shields are strikingly similar to those of the Hawaiian volcanoes. [39], Located over the Mid-Atlantic Ridge, a divergent tectonic plate in the middle of the Atlantic Ocean, Iceland is the site of about 130 volcanoes of various types. [12], Interactions between water and lava at shield volcanoes can cause some eruptions to become hydrovolcanic. The large, decentralized shape of Hawaiian volcanoes as compared to their smaller, symmetrical Icelandic cousins[8] can be attributed to rift eruptions. [40] They do not follow the pattern of caldera growth and destruction that other shield volcanoes do; caldera may form, but they generally do not disappear. [33][34][35] The Galápagos Islands are perched on a large lava plateau known as the Galápagos Platform. Typical shield volcanoes found in California and Oregon measure 3 to 4 mi (5 to 6 km) in diameter and 1,500 to 2,000 ft (500 to 600 m) in height,[7] while shield volcanoes in the central Mexican Michoacán–Guanajuato volcanic field average 340 m (1,100 ft) in height and 4,100 m (13,500 ft) in width, with an average slope angle of 9.4° and an average volume of 1.7 km3 (0.4 cu mi). In height they are typically about one twentieth their width. [7][8] Although the term is generally applied to basaltic shields, it has also at times been applied to rarer scutiform volcanoes of differing magmatic composition—principally pyroclastic shields, formed by the accumulation of fragmental material from particularly powerful explosive eruptions, and rarer felsic lava shields formed by unusually fluid felsic magmas. Venus has over 150 shield volcanoes which are much flatter, with a larger surface area than those found on Earth, some having a diameter of more than 700 km (430 mi). La Cumbre is an active shield volcano on Fernandina Island that has been erupting since April 11, 2009. [47] Although the majority of these are long extinct it has been suggested, from observations by the Venus Express spacecraft, that many may still be active. A new shield volcano forms when a crack on the surface of the Earth begins erupting thin layers of basalt lava. [28] Lava tubes can account for a large portion of shield volcano activity; for example, an estimated 58% of the lava forming Kīlauea comes from lava tubes. For this reason these volcanoes are not steep (you can't pile up a fluid that easily runs downhill). These explosive eruptions are drastically different from the usual shield volcanic activity[12] and are especially prevalent at the waterbound volcanoes of the Hawaiian Isles. This accounts for their asymmetrical shape, whereas Icelandic volcanoes follow a pattern of central eruptions dominated by summit calderas, causing the lava to be more evenly distributed or symmetrical. Shield Volcanoes. Sif Mons, a shield volcano on Venus, in a low-angle computer-generated view based on radar data from the Magellan spacecraft. [1] They include the largest volcanoes on earth, such as Tamu Massif and Mauna Loa. [16] In September 2013, a team led by the University of Houston's William Sager announced the discovery of Tamu Massif, an enormous extinct submarine shield volcano of previously unknown origin which, approximately 450 by 650 km (280 by 400 mi) in area, dwarfs all previously known volcanoes on the planet. Increasing viscosity on the part of the lava or shear stress on the part of local topography can morph a pāhoehoe flow into an ʻaʻā one, but the reverse never occurs. A shield volcano is a wide volcano with shallowly-sloping sides. The Geophysics Institute at the National Polytechnic School in Quito houses an international team of seismologists and volcanologists[37] whose responsibility is to monitor Ecuador's numerous active volcanoes in the Andean Volcanic Belt and the Galapagos Islands. These are eruptive features which occur along linear fissure vents and are distinguished from shield volcanoes by the lack of an identifiable primary eruptive center. Flow after flow pours out in all directions from a central summit vent, or group of vents, building a broad, gently sloping cone of flat, domical shape, with a profile much like that of a warrior's shield. [36] They are composed of either tholeiitic olivine or picritic basalt. (Figure 4.3.2), are typically only a few hundred metres in diameter, and few are more than 200 m high. [14] Accounting for this subsidence and for the height of the volcano above the sea floor, the "true" height of Mauna Loa from the start of its eruptive history is about 17,170 m (56,000 ft). Long eruptive periods form cinder cones, which then collapse over time to form calderas. Like Hawaiian volcanoes, their formation initially begins with several eruptive centers before centralizing and concentrating at a single point. The volcanoes follow a distinct evolutionary pattern of growth and death. Shield volcanoes are not limited to Earth; they have been found on Mars, Venus, and Jupiter's moon, Io.[43]. The most active shield volcano in Africa is Nyamuragira. Flow after flow pours out in all directions from a central summit vent, or group of vents, building a broad, gently sloping cone of flat, domical shape, with a profile much like that of a warrior's shield. Of these four forms, shield volcanoes erupt the least viscous lavas. Carr, M.H., 2006, The Surface of Mars, Cambridge, 307 p. Category:Lists of extraterrestrial mountains, "Nepal in new bid to finally settle Mount Everest height", "New Giant Volcano Below Sea Is Largest in the World", Journal of Volcanology and Geothermal Research, "Geochemistry of Lavas from the Emperor Seamounts, and the Geochemical Evolution of Hawaiian Magmatism from 85 to 42 Ma", "Summary of the Pu'u 'Ō 'ō-Kupaianaha Eruption, 1983-present", "Volcanic Galapagos: Formation of an Oceanic Archipelago", "Description: Lava Tubes and Lava Tube Caves", "How Volcanoes Work: Galapagos Shield Volcanoes", "Volcanoes of South America: Galápagos Islands", Institute for Geophysics at National Polytechnic School, "Galapagos volcano erupts, could threaten wildlife", https://en.wikipedia.org/w/index.php?title=Shield_volcano&oldid=1021840363, Short description is different from Wikidata, Wikipedia articles with faulty MA identifiers, Creative Commons Attribution-ShareAlike License, Diagram of the common structural features of a shield volcano, This page was last edited on 6 May 2021, at 23:45. Fissure venting is common in Hawaiʻi; most Hawaiian eruptions begin with a so-called "wall of fire" along a major fissure line before centralizing to a small number of points. Here are 4 of the volcanoes that comprise the big island of Hawai'i. Some volcanoes interact with both. [8] Although the general form of a "typical" shield volcano varies little worldwide, there are regional differences in their size and morphological characteristics. "Shield volcanoes, are built almost entirely of fluid lava flows. [12][19] An example of these parasitic cones is at Puʻu ʻŌʻō on Kīlauea[20]—continuous activity ongoing since 1983 has built up a 2,290 ft (698 m) tall cone at the site of one of the longest-lasting rift eruptions in known history. Notice that the caldera is composed of numerous smaller "cookie-cutter" collapses which have coalesced to form the main caldera. In addition, there is no clear pattern of age between the volcanoes, suggesting a complicated, irregular pattern of creation. 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