Seafloor spreading

Seafloor dispersing is a geologic procedure in i m sorry tectonic plates—large slabs the Earth"s lithosphere—split personally from every other.

You are watching: Evidence for sea floor spreading has come from

Seafloor dispersing is a geologic process in i beg your pardon tectonic plates—large slabs of Earth"s lithosphere—split apart from every other.
Seafloor spreading and also other tectonic activityprocesses are the result of mantle convection. Mantle convection is the slow, churning movement of Earth’s mantle. Convection currents carry heat from the reduced mantle and core come the lithosphere. Convection currents likewise “recycle” lithospheric materials ago to the mantle.
Seafloor spreading occurs in ~ divergent bowl boundaries. As tectonic plates gradually move far from each other, warm from the mantle’s convection currents provides the crust much more plastic and also less dense. The less-dense material rises, often creating a mountain or elevated area that the seafloor.
Eventually, the tardy cracks. Warm magma sustained by mantle convection bubbles approximately fill this fractures and also spills onto the crust. This bubbled-up magma is cooled through frigid seawater to type igneous rock. This absent (basalt) i do not care a brand-new part the Earth’s crust.
Seafloor spreading occurs follow me mid-ocean ridges—large hill ranges increasing from the s floor. The Mid-Atlantic Ridge, for instance, the end the north American plate indigenous the Eurasian plate, and the southern American plate from the african plate. The east Pacific increase is a mid-ocean ridge that runs v the east Pacific Ocean and separates the Pacific plate native the north American plate, the Cocos plate, the Nazca plate, and also the Antarctic plate. The southeast Indian Ridge marks whereby the southern Indo-Australian plate forms a divergent boundary with the Antarctic plate.
Seafloor spreading is not continuous at all mid-ocean ridges. Gradually spreading ridges are the web page of tall, narrow underwater cliffs and mountains. Swiftly spreading ridges have a much more gentle slopes.
The Mid-Atlantic Ridge, for instance, is a slow-moving spreading center. It diffusion 2-5 centimeters (.8-2 inches) every year and also forms an s trench about the dimension of the cool Canyon. The east Pacific Rise, top top the various other hand, is a quick spreading center. It spreads about 6-16 centimeters (3-6 inches) every year. Over there is not an ocean trench in ~ the east Pacific Rise, due to the fact that the seafloor spreading is too quick for one to develop!
The newest, thinnest late on earth is located near the facility of mid-ocean ridge—the actual site of seafloor spreading. The age, density, and thickness that oceanic crust increases with distance from the mid-ocean ridge.
The magnetism of mid-ocean ridges assisted scientists an initial identify the process of seafloor spreading in the early on 20th century. Basalt, the once-molten rock that provides up most brand-new oceanic crust, is a relatively magnetic substance, and scientists began using magnetometers to measure up the magnetism that the s floor in the 1950s. What they discovered was that the magnetism the the ocean floor about mid-ocean ridges was separated into matching “stripes” top top either next of the ridge. The specific magnetism the basalt rock is identified by the Earth’s magnetic field when the magma is cooling.
Scientists identified that the same procedure formed the perfectly symmetrical stripes top top both side of a mid-ocean ridge. The continual process of seafloor spreading separated the stripes in one orderly pattern.
Oceanic crust gradually moves far from mid-ocean ridges and also sites of seafloor spreading. As it moves, it i do not care cooler, more dense, and an ext thick. Eventually, older oceanic late encounters a tectonic boundary with continental crust.
In part cases, oceanic tardy encounters an active plate margin. An energetic plate margin is an actual bowl boundary, wherein oceanic crust and continental tardy crash into each other. Energetic plate spare are frequently the website of earthquakes and also volcanoes. Oceanic crust developed by seafloor dispersing in the east Pacific Rise, for instance, may become component of the Ring that Fire, the horseshoe-shaped sample of volcanoes and also earthquake zones about the Pacific s basin.
In other cases, oceanic late encounters a passive key margin. Passive margins space not bowl boundaries, but areas where a single tectonic bowl transitions indigenous oceanic lithosphere to continental lithosphere. Passive margins are not sites of faults or subduction zones. Special layers that sediment overlay the transitional late of a passive margin. The oceanic late of the Mid-Atlantic Ridge, because that instance, will either become part of the passive margin top top the phibìc American bowl (on the east shore of north America) or the Eurasian plate (on the west shore of Europe).
New geographic functions can be developed through seafloor spreading. The Red Sea, because that example, was produced as the african plate and also the Arabian key tore away from every other. Today, just the Sinai Peninsula connect the Middle eastern (Asia) with North Africa. Eventually, geologists predict, seafloor spreading will completely separate the 2 continents—and sign up with the Red and also Mediterranean Seas.
Mid-ocean ridges and also seafloor dispersing can additionally influence sea levels. Together oceanic tardy moves away from the shallow mid-ocean ridges, it cools and also sinks as it becomes an ext dense. This increases the volume that the s basin and also decreases the sea level. For instance, a mid-ocean ridge system in Panthalassa—an ancient ocean that surrounding the supercontinent Pangaea—contributed to shallower seas and higher sea levels in the Paleozoic era. Panthalassa was an early kind of the Pacific Ocean, which today experiences less seafloor spreading and also has a lot less comprehensive mid-ocean ridge system. This helps describe why sea levels have actually fallen considerably over the past 80 million years.
Seafloor dispersing disproves an early component of the theory of continent drift. Supporters of continental drift initially theorized the the continents moved (drifted) through unmoving oceans. Seafloor spreading proves the the s itself is a website of tectonic activity.
Seafloor dispersing is just one part of key tectonics. Subduction is another. Subduction happens whereby tectonic plates crash into each other instead of spreading apart. In ~ subduction zones, the leaf of the denser key subducts, or slides, in ~ the less-dense one. The denser lithospheric product then melts earlier into the Earth"s mantle.
Seafloor spreading creates new crust. Subduction destroys old crust. The 2 forces roughly balance every other, so the shape and diameter of the earth remain constant.

Earth"s newest crust is developed at website of seafloor spreading—red web page on this map.

Map courtesy NOAA

Seafloor spreading and also rift valleys are usual features at “triple junctions.” Triple junctions room the intersection of three divergent bowl boundaries. The triple junction is the main point where 3 cracks (boundaries) break-up off at around 120° angle from every other.
In the Afar Triple Junction, the African, Somali, and also Arabian bowl are dividing from every other. The an excellent Rift Valley and also Red Sea (a significant site the seafloor spreading) room the result of plate tectonics in the Afar Triple Junction.

area where two or more tectonic bowl are relocating away from each other. Also called an extensional boundary.

the sudden shaking that Earth"s crust resulted in by the relax of energy along error lines or from volcanic activity.

mid-ocean ridge wherein seafloor spreading is occuring at much more than 100 millimeters (4 inches) a year.

scientific instrument supplied to measure up the presence, strength, and also direction the Earth"s magnetic field.

slow activity of Earth"s hard mantle resulted in by convection currents transferring warm from the interior of the planet to the surface.

lithospheric region where oceanic late transitions to continent crust there is no faults or subduction zones.

base level because that measuring elevations. Sea level is figured out by dimensions taken end a 19-year cycle.

movement that tectonic plates resulting in geologic activity such together volcanic eruptions and earthquakes.

massive slab of solid rock consisted of of Earth"s lithosphere (crust and upper mantle). Additionally called lithospheric plate.

See more: How Long Can You Drive With A Bad Heater Core ? What Are The

an opened in the Earth"s crust, v which lava, ash, and also gases erupt, and likewise the cone built by eruptions.


Careers| Newsroom| Privacy Notice| Sustainability Policy| regards to Service| password of Ethics| contact Us

sign up with our community of educators and receive the latest details on nationwide Geographic"s sources for you and also your students.

Educational sources in her Inbox

join our community of educators and receive the latest details on nationwide Geographic"s resources for you and also your students.