What type of crust is found in the south american plate

Perhaps most importantly, no sunlight penetrate s the deepest ocean trenches, making photosynthesis impossible. Organisms that live in ocean trenches have evolve d with unusual adaptation s to thrive in these cold, dark canyon s. In general, life in dark ocean trenches is isolated and slow-moving. Pressure at the bottom of the Challenger Deep, the deepest spot on Earth, is about 12, tons per square meter 8 tons per square inch.

Large ocean animals, such as sharks and whales, cannot live at this crushing depth. Many organisms that thrive in these high-pressure environments lack gas -filled organ s, such as lung s. These organisms, many related to sea stars or jellies, are made mostly of water and gelatinous material that cannot be crushed as easily as lungs or bones.

Many of these creatures navigate the depths well enough to even make a vertical migration of more than 1, meters 3, feet from the bottom of the trench—every day. Even the fish in deep trenches are gelatinous. Several species of bulb-headed snailfish, for example, dwell at the bottom of the Mariana Trench. The bodies of these fishes have been compared to tissue paper. Shallower ocean trenches have less pressure, but may still fall outside the photic or sunlight zone , where light penetrates the water.

Many fish species have adapted to life in these dark ocean trenches. Anglerfish, for instance, use a bioluminescent growth on the top of their heads called an esca to lure prey.

The anglerfish then snaps up the little fish with its huge, toothy jaws. Without photosynthesis, marine communities rely primarily on two unusual sources for nutrient s. Marine snow is mostly detritus , including excrement and the remains of dead organisms such as seaweed or fish. This nutrient-rich marine snow feeds such animals as sea cucumbers and vampire squid. Another source of nutrients for ocean-trench food webs comes not from photosynthesis, but from chemosynthesis. Chemosynthesis is the process in which producer s in the ocean trench, such as bacteria , convert chemical compound s into organic nutrients.

The chemical compounds used in chemosynthesis are methane or carbon dioxide eject ed from hydrothermal vent s and cold seep s, which spew these toxic , hot gases and fluids into the frigid ocean water. One common animal that relies on chemosynthetic bacteria for food is the giant tube worm. Ocean trenches remain one of the most elusive and little-known marine habitats. Until the s, many oceanographer s thought that these trenches were unchanging environments nearly devoid of life.

Even today, most research on ocean trenches has relied on seafloor samples and photographic expedition s. That is slowly changing as explorers delve into the deep—literally.

Two other unmanned expeditions have also explored the Challenger Deep. Engineering submersible s to explore ocean trenches is presents a huge set of unique challenges. Submersibles must be incredibly strong and resilient to contend with strong ocean current s, no visibility, and intense pressure of the Mariana Trench. Engineering a submersible to safely transport people, as well as delicate equipment , is even more challenging.

The sub that took Piccard and Walsh to the Challenger Deep, the remarkable Trieste , was an unusual vessel called a bathyscaphe. To combat deep-sea currents, the sub was designed to spin slowly as it descended. Lights on the sub were not incandescent or fluorescent bulbs, but arrays of tiny LED s that illuminate d an area of about 30 meters feet.

To adapt to the pressure of the deep, the sub was shaped like a sphere —the walls of a square or cylinder -shaped vessel would need to be at least three times thicker to avoid being crushed. Perhaps most startlingly, the Deepsea Challenger itself was designed to compress. The most famous transform boundary is the San Andreas Fault where the Pacific plate that Los Angeles and Hawaii are on is grinding past the North American plate that San Francisco and the rest of the United States is on at the rate of 3 inches a year.

Recently, geologists have stated that San Francisco should expect another disastrous earthquake in the next 30 years. Another important transform boundary is the North Anatolian Fault in Turkey. This powerful fault last ruptured in in Izmit, Turkey which killed 17, people in 48 seconds.

A small amount of geologic activity, known as intraplate activity , does not take place at plate boundaries but within a plate instead. Mantle plumes are pipes of hot rock that rise through the mantle.

The release of pressure causes melting near the surface to form a hotspot. Eruptions at the hotspot create a volcano. Hotspot volcanoes are found in a line. Can you figure out why?

Hint: The youngest volcano sits above the hotspot and volcanoes become older with distance from the hotspot. An animation of the creation of a hotspot chain is seen here. Geologists use some hotspot chains to tell the direction and the speed a plate is moving. Hotspot magmas rarely penetrate through thick continental crust.

One exception is the Yellowstone hotspot. Skip to main content. Plate Tectonics. Plates move as rigid bodies, so it may seem surprising that the North American Plate can be moving at different rates in different places.

The explanation is that plates move in a rotational manner. The North American Plate, for example, rotates counter-clockwise; the Eurasian Plate rotates clockwise. Boundaries between the plates are of three types: divergent i. The plates are made up of crust and the lithospheric part of the mantle Figure Plates are thought to move along the lithosphere-asthenosphere boundary, as the asthenosphere is the zone of partial melting.

It is assumed that the relative lack of strength of the partial melting zone facilitates the sliding of the lithospheric plates. At spreading centres, the lithospheric mantle may be very thin because the upward convective motion of hot mantle material generates temperatures that are too high for the existence of a significant thickness of rigid lithosphere Figure The fact that the plates include both crustal material and lithospheric mantle material makes it possible for a single plate to be made up of both oceanic and continental crust.

Similarly the South American Plate extends across the western part of the southern Atlantic Ocean, while the European and African plates each include part of the eastern Atlantic Ocean. The Pacific Plate is almost entirely oceanic, but it does include the part of California west of the San Andreas Fault.

Divergent boundaries are spreading boundaries, where new oceanic crust is created from magma derived from partial melting of the mantle caused by decompression as hot mantle rock from depth is moved toward the surface Figure Most divergent boundaries are located at the oceanic ridges although some are on land , and the crustal material created at a spreading boundary is always oceanic in character; in other words, it is mafic igneous rock e.

Note that spreading rates are typically double the velocities of the two plates moving away from a ridge. Spreading is hypothesized to start within a continental area with up-warping or doming related to an underlying mantle plume or series of mantle plumes. When a series of mantle plumes exists beneath a large continent, the resulting rifts may align and lead to the formation of a rift valley such as the present-day Great Rift Valley in eastern Africa.

It is suggested that this type of valley eventually develops into a linear sea such as the present-day Red Sea , and finally into an ocean such as the Atlantic. It is likely that as many as 20 mantle plumes, many of which still exist, were responsible for the initiation of the rifting of Pangea along what is now the mid-Atlantic ridge see Figure Convergent boundaries, where two plates are moving toward each other, are of three types, depending on whether oceanic or continental crust is present on either side of the boundary.

The types are ocean-ocean, ocean-continent, and continent-continent. At an ocean-ocean convergent boundary, one of the plates oceanic crust and lithospheric mantle is pushed, or subducted , under the other. Often it is the older and colder plate that is denser and subducts beneath the younger and hotter plate. There is commonly an ocean trench along the boundary. As discussed in the context of subduction-related volcanism in Chapter 4, the significant volume of water within the subducting material is released as the subducting crust is heated.

It is released when the oceanic crust is heats and then rises and mixes with the overlying mantle. The eastward-moving and more dense Nazca Plate is subducting under the western edge of the South American Plate, along the continent's Pacific coast, resulting in the longest convergent boundary on earth. This subduction zone generates frequent large earthquakes.

The collision of these plates is also responsible for lifting the massive Andes Mountains , home to more than potentially active volcanoes, along four Andean Volcanic Belts :.

South American Plate Tectonic.