What is a sea floor spreading
What Happens During the Process of Seafloor Spreading?
Jun 08, · Seafloor spreading occurs along mid-ocean ridges—large mountain ranges rising from the ocean floor. The Mid-Atlantic Ridge, for instance, separates the North American plate from the Eurasian plate, and the South American plate from the African lovetiktokhere.com East Pacific Rise is a mid-ocean ridge that runs through the eastern Pacific Ocean and separates the Pacific plate from the North . Seafloor spreading, theory that oceanic crust forms along submarine mountain zones, known collectively as the mid-ocean ridge system, and spreads out laterally away from them. This idea played a pivotal role in the development of the theory of plate tectonics, which revolutionized geologic thought during the last quarter of the 20th century.
Seafloor spreading is a process that occurs at mid-ocean ridgeswhere new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Earlier theories by Alfred Wegener how to wear feathers in short hair Alexander du Toit of continental drift postulated that continents in motion "plowed" through the fixed and immovable seafloor.
The idea that the seafloor itself moves and also carries the continents with it as it spreads from a central rift axis was proposed by Harold Hammond Hess from How to change format of pictures to jpeg University and Robert Dietz of the U.
Naval Electronics Laboratory in San Diego in the s. In locations where two plates move apart, at mid-ocean ridges, new seafloor is continually formed during seafloor spreading. Seafloor spreading helps explain continental drift in the theory of plate tectonics. When oceanic plates divergetensional stress causes fractures to occur in the lithosphere.
The motivating force for seafloor spreading ridges is tectonic plate slab pull at subduction zonesrather than magma pressure, although there is typically significant magma activity at spreading ridges.
Hydrothermal vents are common at spreading centers. Older rocks will be found farther away from what are the characteristics of a filipino family spreading zone while younger rocks will be found nearer to the spreading zone.
Spreading rate is the rate at which an ocean basin widens due to seafloor spreading. The rate at which new oceanic lithosphere is added to each tectonic plate on either side of a mid-ocean ridge is the spreading half-rate and is equal to half of the spreading rate. Spreading rates determine if the ridge is fast, intermediate, or slow.
In the s, the past record of geomagnetic reversals of Earth's magnetic field was noticed by observing magnetic stripe "anomalies" on the ocean floor. The stripes on one side of the mid-ocean ridge were the mirror image of those on the other side. By identifying a reversal with a known age and measuring the distance of that reversal from the spreading center, the spreading half-rate could be computed. In some locations spreading rates have been found to be asymmetric; the half rates differ on each side of the ridge crest by about five percent.
Seafloor spreading occurs at spreading centers, distributed along the crests of mid-ocean ridges. Spreading centers end in transform faults or in overlapping spreading center offsets. A spreading center includes a seismically active plate boundary zone a few kilometers to tens of kilometers wide, a crustal accretion zone within the boundary zone where the ocean crust is youngest, and an instantaneous plate boundary - a line within the crustal accretion zone demarcating the two separating plates.
In the general case, seafloor spreading starts as a rift in a continental land masssimilar to the Red Sea - East Africa Rift System today. Because less dense objects rise in relation to denser objects, the area being heated becomes a broad dome see isostasy. As the crust bows upward, fractures occur that gradually grow into rifts.
The typical rift system consists of three rift arms at approximately degree angles. These areas are named triple junctions and can be found in several places across the world today.
The separated margins of the continents evolve to form passive margins. Hess' theory was that new seafloor is formed when magma is forced upward toward the surface at a mid-ocean ridge. If spreading continues past the incipient stage described above, two of the rift arms will open while the third arm stops opening and becomes a 'failed rift' or aulacogen.
As the two active rifts continue to open, eventually the continental crust is attenuated as far as it will stretch. At this point basaltic oceanic crust and upper mantle lithosphere begins to form between the separating continental fragments. When one of the rifts opens into the existing ocean, the rift system is flooded with seawater and becomes a new sea.
The Red Sea is an example of a new arm of the sea. The East African rift was thought to be a failed arm that was opening more slowly than the other two arms, but in the Ethiopian Afar Geophysical Lithospheric Experiment  reported that in the Afar regionSeptembera 60 how to equivalent my degree in canada fissure opened as wide as eight meters.
As a result, the new sea will evaporate partially or completely several times before the elevation of the rift valley has been lowered to the point that the sea becomes stable. During this period of evaporation large evaporite deposits will be made in the rift valley. Later these deposits have the potential to become hydrocarbon seals and are of particular interest to petroleum geologists.
Seafloor spreading can stop during the process, but if it continues to the point that the continent is completely severed, then a new ocean basin is created. The Red Sea has not yet completely split Arabia from Africa, but a similar feature can be found on the other side of Africa that has broken completely free.
South America once fit into the area of the Niger Delta. The Niger River has formed in the failed rift arm of the triple junction. As new seafloor forms and spreads apart from the mid-ocean ridge it slowly cools over time. Older seafloor is, therefore, colder than new seafloor, and older oceanic basins deeper than new oceanic basins due to isostasy. If the diameter of the earth remains relatively constant despite the production of new crust, a mechanism must exist by which crust is also destroyed.
The destruction of oceanic crust occurs at subduction zones where oceanic crust is forced under either continental crust or oceanic crust. What happened on may 8th, the Atlantic basin is actively spreading at the Mid-Atlantic Ridge. Only a small portion of the oceanic crust produced in the Atlantic is subducted. However, the plates making up the Pacific Ocean are experiencing subduction along many of their boundaries which causes the volcanic activity in what has been termed the Ring of Fire of the Pacific Ocean.
Spreading centers at slow and intermediate rates exhibit a rift valley while at fast rates an axial high is found within the crustal accretion zone. Since the new oceanic basins are shallower than the old oceanic basins, the total capacity of the world's ocean basins decreases during times of active sea floor spreading. At the Mid-Atlantic Ridge and in other mid-ocean ridgesmaterial from the what is comparative effectiveness research definition mantle rises through the faults between oceanic plates to form new crust as the plates move away from each other, a phenomenon first observed as continental drift.
When Alfred Wegener first presented a hypothesis of continental drift inhe suggested that continents plowed through the ocean crust. This was impossible: oceanic crust is both more dense and more rigid than continental crust. Accordingly, Wegener's theory wasn't taken very seriously, especially in the United States. At first the driving force for spreading was argued to be convection currents in the mantle.
The driver for seafloor spreading in plates with active margins is the weight of the cool, dense, subducting slabs that pull them along, or slab pull. The magmatism at the ridge is considered to be passive upwelling, which is caused by the plates being pulled apart under the weight of their own slabs. However, the Mid-Atlantic what is a sea floor spreading itself is not bordered by plates that are being pulled into subduction zones, except the minor subduction in the Lesser Antilles and Scotia Arc.
In this case the plates are sliding apart over the mantle upwelling in the process of ridge push. The depth of the seafloor or the height of a location on a mid-ocean ridge what is a sea floor spreading a base-level is closely correlated with its age age of the lithosphere where depth is measured. The age-depth relation can be modeled by the cooling of a lithosphere plate     or mantle half-space in areas without significant subduction.
In the mantle half-space model,  the seabed height is determined by the oceanic lithosphere and how to make native american clothes temperature, due to thermal expansion. The simple result is that the ridge height or ocean depth is proportional to the square root of its age. The system is assumed to be at a quasi- steady stateso that the temperature distribution is constant in time, i.
Due to the large velocity, the temperature dependence on the horizontal direction is negligible, and the height at time t i. Both coefficients are related by:. The depth predicted by the square root of seafloor age derived above is too deep for seafloor older than 80 million years. Analysis of depth versus age and depth versus square root of age data allowed Parsons and Sclater  to estimate model parameters for the North Pacific :. Assuming isostatic equilibrium everywhere beneath the cooling plate yields a revised age depth relationship for older sea floor that is approximately correct for what is a sea floor spreading as young as 20 million years:.
Parsons and Sclater concluded that some style of mantle convection must apply heat to the base of the plate everywhere to prevent cooling down below km and lithosphere contraction seafloor deepening at older ages. From Wikipedia, the free encyclopedia. Process at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. See also: Seafloor depth versus age.
November Engel; Harold L. James; B. Leonard eds. Petrologic studies: a volume to honor A. Bibcode : Natur. ISSN S2CID PMID Geophysical Journal International. Bibcode : GeoJ ISSN X. Annual Review of Earth and Planetary Sciences. Mid-ocean ridges. New York: Cambridge. ISBN OCLC Geophysical Research Letters. Bibcode : GeoRL.
Bibcode : Sci How to remove hills hoist from ground, Geophysics, Geosystems. Bibcode : Geo Earth and Planetary Science Letters. Timothy; White, Scott M. Bibcode : GGG Bibcode : Tectp. Special Papers.
sea floor spreading The process by which new material that lies under the ocean rises and pushes the existing tectonic plates aside, creating new crust as it does so. notes for sea floor spreading Sea floor spreading is making the Atlantic Ocean wider by a few inches each year. Seafloor spreading definition is - the divergence at mid-ocean ridges of the tectonic plates underlying the oceans that is due to upwelling from the earth's interior of magma which solidifies and adds to the spreading plates. If the oceanic crust reaches a deep sea trench, it sinks into the trench and is lost into the mantle. Scientists now know that the oldest crust is coldest and lies deepest in the ocean because it is less buoyant than the hot new lovetiktokhere.comor spreading is the mechanism for Wegener’s drifting continents.
Seafloor spreading is a geological process which involves the splitting of tectonic plates and their movement away from each other. Like all geological processes which involves tectonic activity, seafloor spreading is caused by mantle convection. Convection currents transfer heat from the core and mantle of the earth up to the lithosphere, and also carry rocks from the lithosphere deep to the mantle.
Seafloor spreading takes place at the boundaries of divergent plates whereby, as the divergent tectonic plates move away from each other, hot convectional currents from the mantle cause the lithosphere the ocean crust to become less-dense, ductile, and brittle, and therefore rise above the surrounding crust to form a submarine mountain.
In most cases, the brittle lithosphere cracks, allowing hot magma pushed by the convectional currents to spill onto the ocean crust forming a new layer of the ocean crust made up of igneous rock. Scientists originally believed that drifting was an occurrence exclusive to continents through continental drifts.
However, technological innovations of the 20th century in the form of precise depth recorders and seismic recorders allowed scientists to discover an immense submarine mountain range which runs under the Atlantic Ocean. Scientists would later establish that the Mid-Atlantic Ridge was part of an extensive submarine mountain chain which ran around the world and spanned more than 40, miles in length. In some sections, the immense mountain chain had deep rifts which ranged between 20 and 30 miles in width and with an average depth of about 1 mile.
Hess argued that the seafloor was formed as a result of the expansion of mid-ocean ridges as they move in opposite directions from the ridge center. The study established that rocks making up the ocean crust were not more than million years in age, making them younger compared to continental crust rocks which have a maximum age of 3 billion years.
Additionally, the researchers established that the sediment cover gradually thinned near a mid-ocean ridge. The process of seafloor spreading leads to the formation of numerous geographical features which can be terrestrial, sub-terrestrial, or marine features.
Seafloor spreading is credited for the formation of the Red Sea as a result of the movement of the Arabian and African tectonic plates away from each other.
The movement of these two tectonic plates is still ongoing, albeit at a slow pace, and geologists believe that after millions of years, Africa and Asia will completely be separated at the Suez Peninsula, causing the Red Sea and the Mediterranean Sea to merge. As the ocean crust moves against the continental crust, the boundary between the two forms an active plate margin which is highly unstable, and the instability causes the active plate margin as the center of earthquakes and volcanic activity.
The main geographical feature formed by the process of seafloor spreading are mid-ocean ridges. Usually, these submarine mountain ranges have a valley running on their spine which is known as a rift and is about a mile in depth. While mid-ocean ridges are a submarine features, in some places, the Mid-ocean ridges in the world are all connected and make the Ocean Ridge, which with a total length of 40, miles is the longest mountain range in the world. Mid-ocean ridges have ongoing geological activity, with scientists believing that they move several inches each year.
Mid-Atlantic Ridge is an example of a mid-ocean ridge, which runs beneath the Atlantic Ocean. The East Pacific Rise is another mid-ocean ridge is which runs on the ocean floor of the Pacific Ocean. The East Pacific Rise has unique submarine volcanic features known as hydrothermal vents which are home to animal species found nowhere else on earth.
The Southeast Indian Ridge runs a total length of about 3, miles between the Macquarie Triple Junction and the Rodrigues Triple Junction, and rises about meters above the Indian Ocean floor along its entire length. The mid-ocean ridge separates the Antarctic Plate from the Australian Plate.
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