1 Seafloor spreading is when tectonic plates split from each other, creating a new oceanic crust. 2 While the Pacific Ocean is slowly shrinking, the Atlantic Ocean is expanding. 3 Some scientists believe that eventually the Pacific Ocean could close completely.
This, coupled with the expansion of the Atlantic Ocean, is why the Pacific Ocean is getting smaller. The Atlantic is home to the Mid-Atlantic Ridge, a mountain range that extends for about 10,000 miles and is the site of seafloor spreading.
The two geological processes that help explain the shrinking of the Pacific Ocean are seafloor spreading and subduction. Seafloor spreading is when tectonic plates split from each other, creating a new oceanic crust.
The Seafloor Is Dissolving Away. And Humans Are to Blame. Carbon emissions are dissolving the seafloor, especially in the Northern Atlantic Ocean. Shown here, Azkorri beach in Basque Country in northern Spain. (Image credit: Inaki Bolumburu/Shutterstock) Climate change reaches all the way to the bottom of the sea.
Due to the presence of subduction zones, the destruction of old crust balances the formation of new seafloor, slowing the growth of the Pacific Ocean. This, coupled with the expansion of the Atlantic Ocean, is why the Pacific Ocean is getting smaller.
The Pacific’s mid-ocean ridge, the East Pacific Rise, is a fast-spreading center, which means it spreads about 3 to 6 inches a year, compared to the Mid-Atlantic Ridge, which expands at a rate of 0.8 to 2 inches a year. Due to the presence of subduction zones, the destruction of old crust balances the formation of new seafloor, slowing the growth of the Pacific Ocean. This, coupled with the expansion of the Atlantic Ocean, is why the Pacific Ocean is getting smaller.
Subduction happens when two tectonic plates collide, and one is forced below another. A denser plate, such as an oceanic plate, subducts under a less dense plate, like a continental plate, and melts once it enters the magma. The areas where these plates crash are called subduction zones. Subduction usually results in the formation of mountain ranges, volcanoes, and deep-sea trenches. The presence of these natural structures helps identify the location of subduction zones.
The two geological processes that help explain the shrinking of the Pacific Ocean are seafloor spreading and subduction. Seafloor spreading is when tectonic plates split from each other, creating a new oceanic crust. This process gradually pushes tectonic plates apart and occurs at underwater mountain ranges called mid-ocean ridges.
Seafloor spreading is when tectonic plates split from each other, creating a new oceanic crust. While the Pacific Ocean is slowly shrinking, the Atlantic Ocean is expanding. Some scientists believe that eventually the Pacific Ocean could close completely. The Pacific Ocean is the world’s largest ocean. It is massive, with an estimated area of 63.8 ...
The future of the Pacific Ocean. As a result of Plate Tectonics, the Earth’s continents are always moving. Scientists believe a new supercontinent will form hundreds of millions of years from now, with four fundamental scenarios believed to be responsible for its creation: Novopangea, Pangea Ultima, Aurica, and Amasia.
The Pacific Ocean is home to a circle of subduction zones called the Ring of Fire, a 24,900 mile-long path along the ocean’s edge. It is home to about 75% of the world’s volcanoes, and 95% of all earthquakes happen there. The Pacific’s mid-ocean ridge, the East Pacific Rise, is a fast-spreading center, which means it spreads about 3 ...
The crash and the cessation of subduction effectively halted the northward course of the Pacific Plate at that time, and it was this event that was responsible for suddenly re-routing the direction of the Pacific Plate 50 million years ago. So in the end, it was a continental-scale fender-bender that gave the Pacific its spectacular bend, according to the new study published in Science Advances .
The research team from University of Oslo carefully collected together a variety of evidence that suggests that the Pacific Plate changed its course about 50 million years ago because an archipelago that previously formed the northern end of the Pacific Plate crashed into eastern Asia at that time.
The archipelago comprised what is known as an island arc: an elongate chain of volcanoes and volcanic rocks formed above a subduction zone (a zone where the seafloor of an oceanic tectonic plate is pushed under another tectonic plate and sinks into the mantle below). The team was able to work out the fiery history of the island arc and its relation to the Hawaiian-Emperor Bend from three key sources of data:
Deep rocks: Island arcs only develop along a subduction zone , so the formation of the island arc should have been accompanied by subduction, and subduction, in turn, is associated with the sinking of oceanic tectonic plates into Earth's interior. The relics of subducted oceanic plates can be "imaged" by seismic waves generated by earthquakes, in much the same way that your bones can be imaged with X-rays during a CT scan. By such seismic imaging techniques we have identified the relics of a subduction system that was formerly located at the northern end of the Pacific Plate, at the same place that the island arc rocks were located according to their magnetic data.
As Hawaii's active volcanoes die in the future, new volcanic islands will appear elsewhere on the Pacific Plate, specifically at spots that replace the Hawaiian Islands above the hot conduit. This process is much like what would happen if you moved a sheet of paper over a stationary candle: the movement of the paper will be recorded as a trail of burn marks from the heat of the candle beneath. Hawaii is presently over the "candle," but in the future it will have moved away from it and the candle will begin singing a new spot on the paper.
Exotic rocks: The pieces of that island arc, which are now found on the peninsula of Kamchatka and in the Japanese Islands , are geologically exotic, meaning that they do not have the same characteristics of other rocks from the same region and were clearly transported from somewhere else—and they specifically reveal that they formed far away from any large continents (like Asia).
But something curious catches the eye about this submerged volcanic chain in the Pacific: it isn't straight. A very conspicuous kink divides the chain into two segments: a mostly west-trending segment (the "Hawaiian Chain') and a mostly north-trending segment (the "Emperor Chain'); the kink between is thus commonly referred to as the "Hawaiian-Emperor Bend." Volcanic rocks sampled from seamounts on either side of the bend have been dated, and indicate that the bend developed approximately 47 million years ago.
Seafloor Spreading. Seafloor spreading is a geologic process in which tectonic plate s—large slabs of Earth's lithosphere —split apart from each other. Seafloor spreading and other tectonic activity processes are the result of mantle convection. Mantle convection is the slow, churn ing motion of Earth’s mantle.
As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense.
As oceanic crust moves away from the shallow mid-ocean ridges, it cools and sinks as it becomes more dense. This increases the volume of the ocean basin and decreases the sea level.
Geographic Features. Oceanic crust slowly moves away from mid-ocean ridges and sites of seafloor spreading. As it move s, it becomes cooler, more dense, and more thick. Eventually, older oceanic crust encounters a tectonic boundary with continental crust. In some cases, oceanic crust encounters an active plate margin.
The oceanic crust of the Mid-Atlantic Ridge, for instance, will either become part of the passive margin on the North American plate (on the east coast of North America) or the Eurasian plate (on the west coast of Europe). New geographic features can be created through seafloor spreading.
The newest, thinnest crust on Earth is located near the center of mid-ocean ridge —the actual site of seafloor spreading. The age, density, and thickness of oceanic crust increases with distance from the mid-ocean ridge. Geomagnetic Reversals.
The Mid-Atlantic Ridge, for instance, is a slow spreading center. It spreads 2-5 centimeters (.8-2 inches) every year and forms an ocean trench about the size of the Grand Canyon. The East Pacific Rise, on the other hand, is a fast spreading center. It spreads about 6-16 centimeters (3-6 inches) every year.
Many ocean floor features are a result of the interactions that occur at the edges of these plates. The shifting plates may collide (converge), move away (diverge) or slide past (transform) each other. As plates converge, one plate may move under the other causing earthquakes, forming volcanoes, or creating deep ocean trenches.
Very little of the ocean floor has been mapped directly. So how do we make maps of the global ocean floor? It turns out that satellites can “see” below the sea surface. With careful processing, small differences in sea surface heights and gravity can reveal detailed maps of the seafloor.
Seamounts named to honor NOAA and partners’ role in ocean exploration. Three seamounts in the Pacific Ocean now bear names honoring the contributions to science made by NOAA and its partners in ocean exploration during a campaign led by the NOAA Ocean Exploration.
Bathymetry , the shape of the ocean floor, is largely a result of a process called plate tectonics. The outer rocky layer of the Earth includes about a dozen large sections called tectonic plates that are arranged like a spherical jig-saw puzzle floating on top of the Earth's hot flowing mantle. Convection currents in the molten mantle cause the plates to slowly move about the Earth a few centimeters each year. Many ocean floor features are a result of the interactions that occur at the edges of these plates.
Beneath the smooth ocean surface extends an underwater landscape as complex as anything you might find on land. While the ocean has an average depth of 2.3 miles, the shape and depth of the seafloor is complex. Some features, like canyons and seamounts, might look familiar, while others, such as hydrothermal vents ...
The continental shelf is an area of relatively shallow water, usually less than a few hundred feet deep, that surrounds land.
After scaling the mid-ocean ridge and traversing hundreds to thousands of miles of abyssal plains, you might encounter an ocean trench. The Mariana Trench, for example, is the deepest place in the ocean at 36,201 feet.
About 5 to 15 percent of the global ocean floor has been mapped in this way, depending on how you define “mapped.”. There is another way to see the depths of the ocean: by measuring the shape and gravity field of Earth, a discipline known as geodesy.
From these seafloor maps, scientists can further refine their understand of the evolution and motion of Earth’s tectonic plates and the continents they carry. They can also improve estimates of the depth of the seafloor in various regions and target new sonar surveys to further refine the details, especially in areas where there is thick sediment. This third map shows the gravity data as a cartographer would represent the seafloor, with darker blues representing deeper areas.
But how does the height of the sea surface (which is what the altimeters measured) tell us something about gravity and the seafloor? Mountains and other seafloor features have a lot of mass, so they exert a gravitational pull on the water above and around them; essentially, seamounts pull more water toward their center of mass. This causes water to pile up in small but measurable bumps on the sea surface. (If you are wondering why a greater mass would not pull the water down, it is because water is incompressible; that is, it will not shrink into a smaller volume.)
But there are ways to visualize what the planet looks like beneath that watery shroud. Sonar-based (sounding) instruments mounted on ships can distinguish the shape ( bathymetry) of the seafloor. But such maps can only be made for places where ships and sonar pass frequently. The majority of such measurements have been made along the major shipping routes of the world, interspersed with results from scientific expeditions over the past two centuries. About 5 to 15 percent of the global ocean floor has been mapped in this way, depending on how you define “mapped.”
Seafloor Features Are Revealed by the Gravity Field. It has been said that we have more complete maps of the surface of Mars or the Moon than we do of Earth. Close to 70 percent of our planet is covered by water, and that water refracts, absorbs, and reflects light so well that it can only penetrate a few tens to hundreds of meters.
David Sandwell of the Scripps Institution of Oceanography and Walter Smith of the National Oceanic and Atmospheric Administration have spent much of the past 25 years negotiating with military agencies and satellite operators to allow them access to measurements of the Earth’s gravity field and sea surface heights.
The map above shows a global view of gravity anomalies, as assembled by Sandwell, Smith, and colleagues. Shades of orange and red represent areas where seafloor gravity is stronger (in milligals) than the global average, a phenomenon that mostly coincides with the location of underwater ridges, seamounts, and the edges of Earth’s tectonic plates. Shades of blue represent areas of lower gravity, corresponding largely with the deepest troughs in the ocean. The second map shows a tighter view of that data along the Mid-Atlantic Ridge between Africa and South America.
The same greenhouse gas emissions that are causing the planet's climate to change are also causing the seafloor to dissolve. And new research has found the ocean bottom is melting away faster in some places than others.
The rise in depth indicates that now that there is more carbon in the ocean, dissolution reactions are happening more rapidly and at shallower depths. This line has moved up and down throughout millennia with natural variations in the Earth's atmospheric makeup. Scientists don't yet know what this alteration in the deep sea will mean for the creatures that live there, according to Earther, but future geologists will be able to see man-made climate change in the rocks eventually formed by today's seafloor. Some current researchers have already dubbed this era the Anthropocene, defining it as the point at which human activities began to dominate the environment.
The ocean is what's known as a carbon sink: It absorbs carbon from the atmosphere. And that carbon acidifies the water. In the deep ocean, where the pressure is high, this acidified seawater reacts with calcium carbonate that comes from dead shelled creatures. The reaction neutralizes the carbon, creating bicarbonate.
The western North Atlantic is where the ocean layer without calcium carbonate has risen 980 feet (300 meters). This depth, called the calcite compensation depth, occurs where the rain of calcium carbonate from dead animals is essentially canceled out by ocean acidity. Below this line, there is no accumulation of calcium carbonate.