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25-712: The formation and characteristics of the Guaymas basin are caused by its location on a mid-ocean ridge system, or a range of underwater volcanoes which occur along divergent plate boundaries .As tectonic plates spread apart, magma flows and hardens on the sea floor, creating a new igneous crust. Meanwhile, sediments from the ocean rapidly deposit on top of the crust, building a thick sill cover. The magma spurs hydrothermal flow which creates thermal and chemical gradients. These gradients lead to dynamic biogeochemical environments, which include features such as high heat flow, hydrothermal plumes , and hydrocarbon seeps, that contribute to

50-424: A chain of volcanoes as the plates move above them. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The alternative plate theory is that the mantle source beneath a hotspot is not anomalously hot, rather the crust above is unusually weak or thin, so that lithospheric extension permits

75-404: A distinction between primary hotspots coming from deep within the mantle and secondary hotspots derived from mantle plumes. The primary hotspots originate from the core/mantle boundary and create large volcanic provinces with linear tracks (Easter Island, Iceland, Hawaii, Afar, Louisville, Reunion, and Tristan confirmed; Galapagos, Kerguelen and Marquersas likely). The secondary hotspots originate at

100-511: A few tens to exist. Hawaii , Réunion , Yellowstone , Galápagos , and Iceland are some of the most active volcanic regions to which the hypothesis is applied. The plumes imaged to date vary widely in width and other characteristics, and are tilted, being not the simple, relatively narrow and purely thermal plumes many expected. Only one, (Yellowstone) has as yet been consistently modelled and imaged from deep mantle to surface. Most hotspot volcanoes are basaltic (e.g., Hawaii , Tahiti ). As

125-402: A major source of submarine earthquakes . A seafloor map will show a rather strange pattern of blocky structures that are separated by linear features perpendicular to the ridge axis. If one views the seafloor between the fracture zones as conveyor belts carrying the ridge on each side of the rift away from the spreading center the action becomes clear. Crest depths of the old ridges, parallel to

150-549: A map in time and space of both spreading rate and polar reversals. Hotspot (geology) In geology , hotspots (or hot spots ) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii , Iceland , and Yellowstone hotspots . A hotspot's position on the Earth's surface is independent of tectonic plate boundaries , and so hotspots may create

175-500: A result, they are less explosive than subduction zone volcanoes, in which water is trapped under the overriding plate. Where hotspots occur in continental regions , basaltic magma rises through the continental crust, which melts to form rhyolites . These rhyolites can form violent eruptions. For example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when

200-432: A structure called a mantle plume . Whether or not such mantle plumes exist has been the subject of a major controversy in Earth science, but seismic images consistent with evolving theory now exist. At any place where volcanism is not linked to a constructive or destructive plate margin, the concept of a hotspot has been used to explain its origin. A review article by Courtillot et al. listing possible hotspots makes

225-564: Is an accepted version of this page In plate tectonics , a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary ) is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts , which eventually become rift valleys . Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges . Current research indicates that complex convection within

250-477: Is now closely linked to the mantle plume hypothesis. The detailed compositional studies now possible on hotspot basalts have allowed linkage of samples over the wider areas often implicate in the later hypothesis, and it's seismic imaging developments. Hotspot volcanoes are considered to have a fundamentally different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries. When one oceanic plate meets another,

275-485: Is sometimes thought to be associated with the phenomenon known as hotspots . Here, exceedingly large convective cells bring very large quantities of hot asthenospheric material near the surface, and the kinetic energy is thought to be sufficient to break apart the lithosphere. Divergent boundaries are typified in the oceanic lithosphere by the rifts of the oceanic ridge system, including the Mid-Atlantic Ridge and

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300-483: The Earth's mantle allows material to rise to the base of the lithosphere beneath each divergent plate boundary. This supplies the area with huge amounts of heat and a reduction in pressure that melts rock from the asthenosphere (or upper mantle ) beneath the rift area, forming large flood basalt or lava flows. Each eruption occurs in only a part of the plate boundary at any one time, but when it does occur, it fills in

325-464: The East Pacific Rise , and in the continental lithosphere by rift valleys such as the famous East African Great Rift Valley . Divergent boundaries can create massive fault zones in the oceanic ridge system. Spreading is generally not uniform, so where spreading rates of adjacent ridge blocks are different, massive transform faults occur. These are the fracture zones , many bearing names, that are

350-567: The Guaymas Basin supports a unique and vibrant ecosystem . Heterotrophs consume organic matter rained down from the productive surface waters, while chemolithoautotrophs degrade hydrocarbons and oxidize sulfur in the hydrothermal fluid (often cycling these compounds with syntrophic partners). Of note are the colonies of Riftia tubeworms, Beggiatoa and other microbial mats , and thermophilic microbes that can withstand hydrothermal temperatures. Divergent boundary This

375-418: The current spreading center, will be older and deeper... (from thermal contraction and subsidence ). It is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the seafloor spreading hypothesis was found. Airborne geomagnetic surveys showed a strange pattern of symmetrical magnetic reversals on opposite sides of ridge centers. The pattern was far too regular to be coincidental as

400-466: The denser plate is forced downward into a deep ocean trench. This plate, as it is subducted, releases water into the base of the over-riding plate, and this water mixes with the rock, thus changing its composition causing some rock to melt and rise. It is this that fuels a chain of volcanoes, such as the Aleutian Islands , near Alaska . The joint mantle plume /hotspot hypothesis originally envisaged

425-504: The feeder structures to be fixed relative to one another, with the continents and seafloor drifting overhead. The hypothesis thus predicts that time-progressive chains of volcanoes are developed on the surface. Examples are Yellowstone , which lies at the end of a chain of extinct calderas, which become progressively older to the west. Another example is the Hawaiian archipelago, where islands become progressively older and more deeply eroded to

450-534: The northwest. Geologists have tried to use hotspot volcanic chains to track the movement of the Earth's tectonic plates. This effort has been vexed by the lack of very long chains, by the fact that many are not time-progressive (e.g. the Galápagos ) and by the fact that hotspots do not appear to be fixed relative to one another (e.g. Hawaii and Iceland ). That mantle plumes are much more complex than originally hypothesised and move independently of each other and plates

475-538: The opening gap as the two opposing plates move away from each other. Over millions of years, tectonic plates may move many hundreds of kilometers away from both sides of a divergent plate boundary. Because of this, rocks closest to a boundary are younger than rocks further away on the same plate. At divergent boundaries, two plates move away from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below. The origin of new divergent boundaries at triple junctions

500-472: The passive rising of melt from shallow depths. The origins of the concept of hotspots lie in the work of J. Tuzo Wilson , who postulated in 1963 that the formation of the Hawaiian Islands resulted from the slow movement of a tectonic plate across a hot region beneath the surface. It was later postulated that hotspots are fed by streams of hot mantle rising from the Earth's core–mantle boundary in

525-516: The rhyolite is completely erupted, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures (cracks in the lithosphere). An example of this activity is the Ilgachuz Range in British Columbia, which was created by an early complex series of trachyte and rhyolite eruptions, and late extrusion of a sequence of basaltic lava flows. The hotspot hypothesis

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550-457: The type of ecosystem which thrives in the Guaymas basin. Hydrothermal circulation, or the circulation of hot water, is a predominant feature of the Guaymas Basin. Hydrothermalism is mainly observed in the southern trough of the basin where hydrothermal vents make up a hydrothermal complex on the seafloor by creating mounds, chimney structures, and sediments. Hydrothermal circulation happens when water flows downward through broken ocean crust along

575-526: The upper/lower mantle boundary, and do not form large volcanic provinces, but island chains (Samoa, Tahiti, Cook, Pitcairn, Caroline, MacDonald confirmed, with up to 20 or so more possible). Other potential hotspots are the result of shallow mantle material surfacing in areas of lithospheric break-up caused by tension and are thus a very different type of volcanism. Estimates for the number of hotspots postulated to be fed by mantle plumes have ranged from about 20 to several thousand, with most geologists considering

600-411: The volcanic mid-ocean ridge system. After being heated, the water chemically reacts with the host sill. The temperature of the water can rise above 400°C. At this temperature, the water will rise quickly back to the seafloor due to its decrease in density. This circulation of water is crucial to the cycling of energy and nutrients between the ocean crust and the ocean. Especially in the southern trough,

625-478: The widths of the opposing bands were too closely matched. Scientists had been studying polar reversals and the link was made by Lawrence W. Morley , Frederick John Vine and Drummond Hoyle Matthews in the Morley–Vine–Matthews hypothesis . The magnetic banding directly corresponds with the Earth's polar reversals. This was confirmed by measuring the ages of the rocks within each band. The banding furnishes

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