85-595: Vulcanodon (meaning " volcano tooth ") is an extinct genus of sauropod dinosaur from the Early Jurassic Uppermost Forest Sandstone of southern Africa . The only known species is V. karibaensis . Discovered in 1969 in Zimbabwe , it was regarded as the earliest-known sauropod for decades, and is still one of the most primitive sauropods that has been discovered. As a quadrupedal , ground-dwelling herbivore , Vulcanodon already showed
170-535: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Isanosaurus Isanosaurus ("North-eastern thailand lizard") is an extinct genus of sauropod dinosaur from Thailand . It was originally dated to approximately 210 million years ago during the Late Triassic (late Norian to Rhaetian stages), which would make it one of
255-842: A mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift , the Wells Gray-Clearwater volcanic field , and the Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from
340-437: A graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories. The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater. While there is no international consensus among volcanologists on how to define an active volcano,
425-441: A hill slope and was partially eroded by surface exponation and plant roots, erroneously documented as sandwiched between two basalt layers. It includes the pelvis and sacrum, most of the left hind limb and foot, a right thigh bone, and twelve anterior tail vertebrae. These remains pertain to a single individual as they were all found articulated (still connected together). Additionally, several disarticulated bones were found, including
510-443: 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. See § Volcanoes on other celestial bodies and cryovolcano for more information. The word volcano
595-540: A prosauropod because of the knife-shaped teeth found near its fossils , which fit in with the idea that prosauropods were omnivorous . Scientists now know that the teeth belonged to an unidentified theropod that may have scavenged on the Vulcanodon carcass . Vulcanodon is now known to be a true sauropod. Upon the discovery of the related Tazoudasaurus , both animals were unified in the family Vulcanodontidae , though this has not been universally accepted. Vulcanodon
680-485: A sauropod but as an advanced , specialized prosauropod, possibly of the family Melanorosauridae . According to Raath, the sauropod-like limb proportions in Vulcanodon evolved independently from those of true sauropods (through convergent evolution ). He argued that primitive features of the pelvis as well as the knife-shaped teeth preclude a classification within the Sauropoda. The teeth, however, are now known to belong to
765-563: A scientific symposium in Cape Town and a brief note was published. The find was formally named and described in July 1972 by paleontologist Michael Raath. The name Vulcanodon ( lat. Vulcanus – Roman god of fire; gr. odon – "tooth") points to the fact that the skeleton was found in sandstone , that was at the time misinterpreted to be part of the Batoka Formation but is actually part of
850-462: A second, six tail vertebra, two chevrons , fragmentary ribs, the right sternal plate , the right shoulder blade , and the left thigh bone (femur). This individual may have measured 6.5 metres (21 ft) when alive; the thigh bone measures 76 centimetres in length. However, the vertebral neural arches have been found separated from the vertebral centra , indicating that these elements were not fused with each other; thus, this individual probably
935-608: A single sauropod tail vertebra from the Upper Elliot Formation of South Africa that may belong to a genus closely related to Vulcanodon . The Upper Elliot Formation is famous for its abundant fossils of the prosauropod Massospondylus . Vulcanodon in a cladogram after Nair et al ., 2012: Vulcanodon Tazoudasaurus Spinophorosaurus Barapasaurus Rhoetosaurus Shunosaurus Patagosaurus Omeisaurus Mamenchisaurus Losillasaurus Haplocanthosaurus Neosauropoda During
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#17328798663061020-403: A theropod. Arthur Cruickshank (1975) was the first to show that Vulcanodon was indeed a sauropod, arguing that the fifth metatarsal bone was equally long as the remaining metatarsals, a condition seen in other sauropods but not in prosauropods. Today, Vulcanodon is universally accepted to be one of the most basal (primitive) members of Sauropoda. Michael Cooper (1984) erected a new family ,
1105-632: A volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases. Lava can be broadly classified into four different compositions: Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced [ˈʔaʔa] ) and pāhoehoe ( [paːˈho.eˈho.e] ), both Hawaiian words. ʻAʻa
1190-555: A volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behaviour of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus . Vents that issue volcanic material (including lava and ash ) and gases (mainly steam and magmatic gases) can develop anywhere on
1275-465: A volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometres (240 cu mi) of volcanic deposits in a single explosive event. Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera -forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivalling those of flood basalts . Supervolcano eruptions, while
1360-727: Is a volcanic field of over 60 cinder cones. Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon. Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and tephra in alternate layers, the strata that gives rise to the name. They are also known as composite volcanoes because they are created from multiple structures during different kinds of eruptions. Classic examples include Mount Fuji in Japan, Mayon Volcano in
1445-445: Is a rupture in the crust of a planetary-mass object , such as Earth , that allows hot lava , volcanic ash , and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism . On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example,
1530-412: Is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse. More silicic lava flows take the form of block lava, where
1615-568: Is composed primarily of flood basalts. The skeleton was found near the top of a 30-metre-thick (98 ft) bedded layer of sand- and siltstone that is over- and underlain by flood basalts. It was long assumed that Vulcanodon lived during the lowermost (earliest) part of the Jurassic (the Hettangian stage ) or at the Triassic – Jurassic boundary, approximately 200 million years ago. Therefore, it
1700-554: Is derived from the name of Vulcano , a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan , the god of fire in Roman mythology . The study of volcanoes is called volcanology , sometimes spelled vulcanology . According to the theory of plate tectonics, Earth's lithosphere , its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in
1785-567: Is expressed using the volcanic explosivity index (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions. As of December 2022 , the Smithsonian Institution 's Global Volcanism Program database of volcanic eruptions in the Holocene Epoch (the last 11,700 years) lists 9,901 confirmed eruptions from 859 volcanoes. The database also lists 1,113 uncertain eruptions and 168 discredited eruptions for
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#17328798663061870-524: Is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analysed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near
1955-466: Is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland , as well. Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens , but can also form independently, as in
2040-600: The Cascade Volcanoes or the Japanese Archipelago , or the eastern islands of Indonesia . Hotspots are volcanic areas thought to be formed by mantle plumes , which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off
2125-629: The Forest Sandstone lays a few metres below the lava flows of the Batoka Formation, and emphasizes the peculiar knife-shaped teeth that are now known to belong to a theropod. The specific name , karibaensis , refers to the place of discovery on a small island in Lake Kariba. It was one of the first dinosaurs found in Zimbabwe. The skeleton (catalogue number QG24) has been found weathering out of
2210-597: The Nam Phong Formation near the village of Ban Non Thaworn, in Chaiyaphum Province . When discovered in 1998, the skeleton had unfortunately been mostly eroded away. With regard to vertebrate fossils, the Nam Phong Formation is poorly explored: besides Isanosaurus , only two articulated ischia were found. Whether these ischia belong to Isanosaurus is unclear, because no pelvic bones are preserved in
2295-659: The Vulcanodontidae , which he regarded as the "rootstock" for later sauropod families. Originally, the Vulcanodontidae included Vulcanodon and the Indian Barapasaurus , but subsequent studies attributed a number of other, much more fragmentary early sauropod genera to this family, including Ohmdenosaurus and Zizhongosaurus . Paul Upchurch (1995) showed that Barapasaurus was more closely related to later, more advanced sauropods than to Vulcanodon , rendering
2380-792: The core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. Mars has significant volcanoes. In 2009,
2465-535: The holotype specimen. Isanosaurus was described by French palaeontologist Éric Buffetaut and colleagues in 2000. The name is derived from Isan (north-eastern Thailand); the species name honours P. Attavipach, a supporter of palaeontological research in Thailand and former Director General of the Thai Department of Mineral Resources . The only specimen includes a neck vertebra , a back vertebra and part of
2550-824: The landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō in New Zealand. Some volcanoes can be low-relief landform features, with the potential to be hard to recognize as such and be obscured by geological processes. Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter , Saturn , and Neptune ; and mud volcanoes , which are structures often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when
2635-489: The "Vulcanodon beds". The sediments in which Vulcanodon was found may represent distal alluvial fan deposits which levelled off into a desert landscape, which may have contained lakes during the wet season. The individual may have roamed the shores of wadis that cut into the alluvial fan deposits, unless the carcass was transported to the locality it was found by flooding. Initially, sauropods were thought to be mainly aquatic, inhabiting lush peat swamps and being captive to
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2720-612: The Philippines, and Mount Vesuvius and Stromboli in Italy. Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like
2805-609: The USGS defines a volcano as active whenever subterranean indicators, such as earthquake swarms , ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present. The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again. Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in
2890-575: The Vulcanodontidae polyphyletic and therefore invalid. The exact relationships with other basal sauropod genera remain unclear. Ronan Allain and colleagues (2004, 2008) found that Vulcanodon is most closely related to Tazoudasaurus , a newly discovered sauropod genus from Morocco . These researchers suggested reintroducing the name Vulcanodontidae to name the clade containing Vulcanodon and Tazoudasaurus . However, this sibling relationship between Tazoudasaurus and Vulcanodon could not be confirmed by other analyses. Adam Yates (2004) described
2975-503: The boundary with the Yukon Territory . Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity. The largest structures are 10 kilometres in diameter and reach 700 meters high. The material that is expelled in a volcanic eruption can be classified into three types: The concentrations of different volcanic gases can vary considerably from one volcano to
3060-533: The buoyancy of water to support their giant body weights. In 1984, Cooper pointed out that Vulcanodon , the most primitive sauropod known at that time, lived in a desert like environment and therefore must have been terrestrial. This indicated that the large body size of sauropods, as already seen in Vulcanodon , had not evolved as an adaptation to an aquatic life style. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Volcano A volcano
3145-402: The case of Lassen Peak . Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent. Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down
3230-400: The closely related Tazoudasaurus . As was assumed that the locality of Vulcanodon itself cannot be dated radiometrically because of weathering of the lavas, it would roughly be a contemporary to Karoo lavas from other localities, as the entire sequence of volcanic eruptions was finished within one million years. In 2018 was revelated that as in 2016 Lake Kariba hosted record-low water levels
3315-561: The earliest and basalmost sauropods, it is important for understanding the early evolution of this group. Sauropods descend from basal sauropodomorphs (informally called "prosauropods"), which were primitively bipedal (two-legged). While Vulcanodon already was fully quadrupedal (four-legged), its limb proportions were intermediate between those of its prosauropod ancestors and those of later, more derived sauropods. Its forelimbs were much more similar to later sauropods than basal sauropodomorphs because they are straight, much more gracile, and
3400-772: The enormous area they cover, and subsequent concealment under vegetation and glacial deposits, supervolcanoes can be difficult to identify in the geologic record without careful geologic mapping . Known examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States); Lake Taupō in New Zealand; Lake Toba in Sumatra , Indonesia; and Ngorongoro Crater in Tanzania. Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas in
3485-419: The features found in sauropods that basal sauropodomorphs lack are related to the change in body size. The greatest regions affected by this are the hind limbs and pelvis. For example, an elongating of the ilium , size reduction of the lesser trochanter shelf, and semiplantigrade posture are some features that indicate the amount and positioning of leg muscles being modified. Vulcanodon possessed these features,
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3570-538: The femur were reduced in Isanosaurus ; most notably, the lesser trochanter was lacking. Additional important features can be found in the vertebrae. The neck vertebrae were distinctly opisthocoelous (convex at the front and hollow at the back), forming ball-and-socket joints with neighbouring vertebrae. The tail vertebrae, on the other hand, were amphicoelous (concave at both ends). The dorsal neural spines were very high, like those of some later sauropods, unlike
3655-431: The flow is covered with angular, vesicle-poor blocks. Rhyolitic flows typically consist largely of obsidian . Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface . These violent explosions produce particles of material that can then fly from
3740-592: The formation of a submarine volcano off the coast of Mayotte . Subglacial volcanoes develop underneath ice caps . They are made up of lava plateaus capping extensive pillow lavas and palagonite . These volcanoes are also called table mountains, tuyas , or (in Iceland) mobergs. Very good examples of this type of volcano can be seen in Iceland and in British Columbia . The origin of the term comes from Tuya Butte , which
3825-568: The future. In an article justifying the re-classification of Alaska's Mount Edgecumbe volcano from "dormant" to "active", volcanologists at the Alaska Volcano Observatory pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in
3910-461: The glossaries or index", however the USGS still widely employs the term. Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the Chaitén volcano in 2008. Modern volcanic activity monitoring techniques, and improvements in
3995-492: The interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split. A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen ), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites . Examples include
4080-514: The later part of the Lower Jurassic, southern Africa was the scene of massive volcanism , resulting in extensive lava flows (so called flood basalts ) that covered much of southern Africa and Antarctica . These basalt formations are known as the Karoo-Ferrar large igneous province. Vulcanodon comes from the "Vulcanodon beds", a fossil-bearing sediment unit within the Batoka Formation , which
4165-522: The latter of which is seen earliest in it. However, Vulcanodon does not have reduced distal phalanges, which are seen in Shunosaurus and all more derived sauropods. This means that while the muscle positioning of its legs were changing, they had not yet reduced in the distal region of the limb. Vulcanodon is known only from a single locality on an island in Lake Kariba , the largest artificial lake in
4250-419: The mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland . Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. The oceanic plate subducts (dives beneath the continental plate), forming a deep ocean trench just offshore. In a process called flux melting , water released from the subducting plate lowers the melting temperature of
4335-545: The modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale. For example, the Yellowstone volcano has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius
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#17328798663064420-415: The most dangerous type, are very rare; four are known from the last million years , and about 60 historical VEI 8 eruptions have been identified in the geologic record over millions of years. A supervolcano can produce devastation on a continental scale, and severely cool global temperatures for many years after the eruption due to the huge volumes of sulfur and ash released into the atmosphere. Because of
4505-438: The mud volcano is actually a vent of an igneous volcano. Volcanic fissure vents are flat, linear fractures through which lava emerges. Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle effusive eruptions . Since low-viscosity magma
4590-452: The next. Water vapour is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide . Other principal volcanic gases include hydrogen sulfide , hydrogen chloride , and hydrogen fluoride . A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen , carbon monoxide , halocarbons , organic compounds, and volatile metal chlorides. The form and style of an eruption of
4675-867: The north side of the mountain. Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 metres (100 to 1,300 ft) high. Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings . Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico , Caja del Rio
4760-541: The ocean surface as new islands or floating pumice rafts . In May and June 2018, a multitude of seismic signals were detected by earthquake monitoring agencies all over the world. They took the form of unusual humming sounds, and some of the signals detected in November of that year had a duration of up to 20 minutes. An oceanographic research campaign in May 2019 showed that the previously mysterious humming noises were caused by
4845-420: The ocean surface, due to the rapid cooling effect and increased buoyancy in water (as compared to air), which often causes volcanic vents to form steep pillars on the ocean floor. Hydrothermal vents are common near these volcanoes, and some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break
4930-471: The ocean's surface. In the deep ocean basins, the tremendous weight of the water prevents the explosive release of steam and gases; however, submarine eruptions can be detected by hydrophones and by the discoloration of water because of volcanic gases . Pillow lava is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form underwater. Even large submarine eruptions may not disturb
5015-408: The oldest known sauropods. Its age was later considered uncertain, and may be Early Jurassic or even as young as Late Jurassic . The only species is Isanosaurus attavipachi . Though important for the understanding of sauropod origin and early evolution, Isanosaurus is poorly known. Exact relationships to other early sauropods remain unresolved. The specimen was found in dark red sandstone of
5100-462: The one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars . Large pieces of tephra are called volcanic bombs . Big bombs can measure more than 1.2 metres (4 ft) across and weigh several tons. A supervolcano is defined as
5185-425: The overlying mantle wedge, thus creating magma . This magma tends to be extremely viscous because of its high silica content, so it often does not reach the surface but cools and solidifies at depth . When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs . Typical examples are the volcanoes in the Pacific Ring of Fire , such as
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#17328798663065270-569: The pelvis, a posture called death pose that is frequently seen in dinosaur skeletons. The teeth would have been the only preserved elements of the skull. However, as shown by Cooper (1984), these teeth do not pertain to Vulcanodon but to a theropod dinosaur that may have scavenged on the Vulcanodon carcass. Antetonitrus Gongxianosaurus Isanosaurus Vulcanodon Tazoudasaurus Barapasaurus Patagosaurus Omeisaurus Mamenchisaurus Neosauropoda Originally, Michael Raath (1972) described Vulcanodon not as
5355-595: The plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain , with the Yellowstone Caldera being part of the North American plate currently above the Yellowstone hotspot . However, the mantle plume hypothesis has been questioned. Sustained upwelling of hot mantle rock can develop under
5440-435: The proximal end of the ulna is v-shaped. Unfortunately, no skull or neck of Vulcanodon is known, although it is otherwise very well known. Vulcanodon ' s limbs were sturdy and column-like, and its forelimbs were already proportionally long, reaching 76% of hindlimb length. Its lower leg, metatarsus , and toes were shortened in comparison to its bipedal ancestors, but still not as short as in later sauropods. The sacrum
5525-408: The right forearm and some metacarpalia and phalanges from both the right and left forefeet, probably also pertaining to this individual. Later, the site was revisited by the scientists Geoffrey Bond and Michael Cooper, who were able to collect additional remains including a scapula (specimen QG152, a shoulder blade) and a fragment of a neck vertebra. These remains show that more than one individual
5610-435: The same time interval. Volcanoes vary greatly in their level of activity, with individual volcanic systems having an eruption recurrence ranging from several times a year to once in tens of thousands of years. Volcanoes are informally described as erupting , active , dormant , or extinct , but the definitions of these terms are not entirely uniform among volcanologists. The level of activity of most volcanoes falls upon
5695-485: The same way; they are often described as "caldera volcanoes". Submarine volcanoes are common features of the ocean floor. Volcanic activity during the Holocene Epoch has been documented at only 119 submarine volcanoes, but there may be more than one million geologically young submarine volcanoes on the ocean floor. In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above
5780-449: The skeleton, the pelvis was relatively primitive, reminiscent of its "prosauropod" ancestors. One such feature is that the brevis shelf of the ilium has a fossa, which is not found in any more derived sauropods. The hallux (the first toe of the foot) showed a large claw that was flattened laterally, as seen in "prosauropods". However, the claws of the second and third toe were unusual in being nail-like and broader than deep. This feature
5865-622: The solidified erupted material that makes up the mantle of a volcano may be stripped away that its inner anatomy becomes apparent. Using the metaphor of biological anatomy , such a process is called "dissection". Cinder Hill , a feature of Mount Bird on Ross Island , Antarctica , is a prominent example of a dissected volcano. Volcanoes that were, on a geological timescale, recently active, such as for example Mount Kaimon in southern Kyūshū , Japan , tend to be undissected. Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions. The intensity of explosive volcanism
5950-406: The surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes that were once thought to be extinct, before springing back into eruptive activity were the long-dormant Soufrière Hills volcano on the island of Montserrat , thought to be extinct until activity resumed in 1995 (turning its capital Plymouth into
6035-434: The theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region. At the mid-ocean ridges , two tectonic plates diverge from one another as hot mantle rock creeps upwards beneath
6120-444: The thinned oceanic crust . The decrease of pressure in the rising mantle rock leads to adiabatic expansion and the partial melting of the rock, causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new seafloor . Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where
6205-413: The typical sauropod body plan with column-like legs and a long neck and tail. It was smaller than most other sauropods, measuring approximately eleven metres (36 ft) in length. Vulcanodon is known from a fragmentary skeleton including much of the pelvic girdle , hindlimbs, forearms, and tail, but lacking the trunk and neck vertebrae as well as the skull . Originally, this genus was believed to be
6290-431: The underlying ductile mantle , and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created). During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in
6375-665: The unit were accessible to be studied and confirmed that the holotype came from the uppermost Forest Sandstone, being as old as the Rhaetian or as young as the Pliensbachian, with a Sinemurian-Pliensbachian Midpoint. Vulcanodon is the only named dinosaur from the Vulcanodon beds. Cooper (1984) noted that the habitat was desert-like, as indicated by aeolian (wind-blown) sands of the Forest Sandstone Formation, which underlies
6460-492: The volcano. Solid particles smaller than 2 mm in diameter ( sand-sized or smaller) are called volcanic ash. Tephra and other volcaniclastics (shattered volcanic material) make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record. The production of large volumes of tephra is characteristic of explosive volcanism. Through natural processes, mainly erosion , so much of
6545-424: The volcanoes of the East African Rift . 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. The most common perception of
6630-462: The world, in northern Zimbabwe (formerly Rhodesia ). The island, located west of Bumi Hills , is called "Island 126/127", after early, unpublished lake charts, but has no formal name. The first bone was found by B. A. Gibson of the town of Kariba in July 1969, and an excavation team collected the specimen in October 1969, March 1970 and May 1970. In the later half of 1970, the new find was presented at
6715-430: Was also found in the probably closely related Tazoudasaurus , but is absent in all other sauropods. The feet of Vulcanodon were semiplantigrade as in later sauropods (where both the digits and part of the metatarsals contact the ground), a derived feature not found in more basal sauropods like Isanosaurus . However, they also retained primitive features, like the fact that the phalanges were not reduced. Many of
6800-421: Was described by Roman writers as having been covered with gardens and vineyards before its unexpected eruption of 79 CE , which destroyed the towns of Herculaneum and Pompeii . Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness. Pinatubo was an inconspicuous volcano, unknown to most people in
6885-411: Was initially thought have been a small sauropod. In 2010, Gregory S. Paul estimated its length at 11 metres (36.1 ft), its weight at 3.5 tonnes (3.9 short tons). Some books mention lower estimates of approximately 6.5 m (21 ft). However, in 2018, researchers have estimated a greater body mass of 10.3 metric tons (11.4 short tons). The thighbone was 110 centimetres (43 in) long. As one of
6970-411: Was made out of four fused sacral vertebrae; "prosauropods" possessed only three sacrals. The tail vertebra bodies already showed an incipient excavation of their lateral sides, saving weight and giving them a waisted appearance when viewed from below. In later sauropods, this excavations were enlarged to form extensive perforated pockets called pleurocoels . Contrasting the many sauropod-like features of
7055-474: Was not fully grown. Early sauropodomorphs were primitively bipedal (two-legged). Isanosaurus , being one of the first sauropods known, already shows a quadrupedal locomotion (with all four legs on the ground). The legs were column-like, as indicated by the robust and straight thigh bone. In prosauropods , but also in the very basal sauropod Antetonitrus , the thigh bone was slightly sigmoidal (S-curved). Also, like in other sauropods, bony processes of
7140-520: Was present, and it is possible that they do not pertain to Vulcanodon at all. Today, the Vulcanodon remains are stored in the Natural History Museum of Zimbabwe in Bulawayo . Raath (1972) noted the discovery of nine fragmentary carnivorous teeth near the pelvic region of the skeleton. He argued that the Vulcanodon carcass might have been embedded with the head and neck bended backwards above
7225-452: Was regarded as the earliest sauropod known, until the discovery of the even older Late Triassic Isanosaurus was announced in 2000 . Adam Yates (2004) has recently shown that Vulcanodon is actually much younger than previously thought, dating to the uppermost (latest) part of the Lower Jurassic during the Toarcian stage, approximately 175–183 million years ago. Thus, it is contemporary to
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