It is home to the Challenger Deep, which, at 10, meters 35, feet , is the deepest part of the ocean. The Tonga, Kuril-Kamatcha, Philippine, and Kermadec Trenches all contain depths greater than 10, meters 33, feet.
The great depth of ocean trenches creates an environment with water pressures more than 1, times greater than the surface, constant temperatures just above freezing, and no light to sustain photosynthesis. While this may not seem like conditions suitable to life, the combination of extremely high pressure, the gradual accumulation of food along trench axes, and the geographical isolation of hadal systems are believed to have created habitats with an extraordinarily high abundance of a few highly specialized organisms.
Many of the organisms living in trenches have evolved surprising ways to survive in these unique environments. Recent discoveries in the hadal zone have revealed organisms with proteins and biomolecules suited to resisting the crushing hydrostatic pressure and others able to harness energy from the chemicals that leak out of hydrocarbon seeps and mud volcanoes on the seafloor.
Other hadal species thrive on the organic material that that drifts down from the sea surface and is funneled to the axis of the V-shaped trenches. Because of their extreme depth, trenches present unique logistical and engineering challenges for the researchers who want to study them. Trench exploration to date has been extremely limited only three humans have ever visited the seafloor below 6, meters and much of what is known about trenches and the things that live there has been derived from two sampling campaigns in the s the Danish G alathea and the Soviet Vitjaz Expeditions and from a handful of photographic expeditions and seafloor samples taken remotely from the deep with little knowledge of their precise location.
Despite their scarcity, these initial attempts at studying trenches have hinted at the existence of previously unknown processes, species, and ecosystems. Knowledge of ocean trenches is limited because of their depth and their remoteness, but scientists do know they play a significant role in our lives on land.
Seafloor earthquakes generated in subduction zones were responsible for the Indian Ocean tsunami and for the Tohoku Earthquake and tsunami in Japan. By studying ocean trenches, scientists can better understand the physical process of subduction and the causes of these devastating natural disasters. The study of trenches also gives researchers insight into the novel and diverse adaptations of deep-sea organisms to their surroundings that may hold the key to biological and biomedical advances.
Studying the way that hadal organisms have adapted to life in their harsh surroundings could help advance understanding in many different areas of research, from diabetes treatments to improved laundry detergents. Researchers have already discovered microbes inhabiting deep-sea hydrothermal vents that hold potential as new sources of antibiotics and anti-cancer drugs. The discovery presents opportunities for further research on the role of trenches both as a source through volcanism and other processes and a sink in the planetary carbon cycle that could influence the way scientists eventually come to understand and predict the impacts of human-generated greenhouse gases and global climate change.
The development of new deep-sea technology, from submersibles to cameras to sensors and samplers, will provide greater opportunity for scientists to systematically investigate trench ecosystems over extended periods of time. This will eventually give us a better understanding of earthquakes and geophysical processes, revise how scientists understand the global carbon cycle, provide avenues for biomedical research, and potentially contribute new insights into the evolution of life on earth.
These same technological advances will also create new capabilities for scientists to study the entire ocean, from remote coastlines to the ice-covered Arctic Ocean. Trenches are long, narrow depressions on the seafloor that form at the boundary of tectonic plates where one plate is pushed, or subducts, beneath another. The deepest parts of the ocean are found in trenches—at more than 35, feet nearly 11, meters , Challenger Deep is a part of the Mariana Trench, where the Pacific Plate is subducting beneath the Philippine Plate.
This digital photo essay brings you the forms, figures, and facts of life more than a mile and half deep. Andy Bowen has been developing robotic deep-sea technology for many years, starting his career at Woods Hole Oceanographic Institution in…. It took a village of engineers to build a completely new type of unmanned deep-sea robot that can reach the…. Provides researchers access to some of the most remote areas on Earth, in autonomous or remotely operated mode. He uses techniques that span isotope geochemistry, next generation DNA sequencing, and satellite tagging to study the ecology of a wide variety of ocean species.
He recently discovered that blue sharks use warm water ocean tunnels, or eddies, to dive to the ocean twilight zone, where they forage in nutrient-rich waters hundreds of meters down. Born in New Zealand, Simon received his B.
With much of his work in the South Pacific and Caribbean, Simon has been on many cruises, logging 1, hours of scuba diving and hours in tropical environs. Once this happens, the continents will no longer continue to move apart because the spreading at the mid-Atlantic ridge will be taken up by subduction. If spreading along the mid-Atlantic ridge continues to be slower than spreading within the Pacific Ocean, the Atlantic Ocean will start to close up, and eventually in a million years or more North and South America will collide with Europe and Africa.
There is strong evidence around the margins of the Atlantic Ocean that this process has taken place before. The roots of ancient mountain belts, which are present along the eastern margin of North America, the western margin of Europe, and the northwestern margin of Africa, show that these land masses once collided with each other to form a mountain chain, possibly as big as the Himalayas. The apparent line of collision runs between Norway and Sweden, between Scotland and England, through Ireland, through Newfoundland, and the Maritimes, through the northeastern and eastern states, and across the northern end of Florida.
When rifting of Pangea started at approximately Ma, the fissuring was along a different line from the line of the earlier collision. This is why some of the mountain chains formed during the earlier collision can be traced from Europe to North America and from Europe to Africa.
That the Atlantic Ocean rift may have occurred in approximately the same place during two separate events several hundred million years apart is probably no coincidence. The series of hot spots that has been identified in the Atlantic Ocean may also have existed for several hundred million years, and thus may have contributed to rifting in roughly the same place on at least two separate occasions Figure This map shows the boundaries between the major plates.
Without referring to the plate map in Figure Start with the major plates, and then work on the smaller ones. Finally, using a highlighter or coloured pencil, label as many of the boundaries as you can as divergent, convergent, or transform. Skip to content Chapter 10 Plate Tectonics. Figure Previous: Next: Share This Book Share on Twitter.
This plate includes all of Africa and the surrounding ocean, including the eastern Atlantic Ocean, the surrounding Antarctic Ocean, and the western Indian ocean.
The part of the plate around the South America plate is moving northwards and a little east. The part of the plate around the Australia plate is moving southwards. This plate includes Australia and much of the surrounding ocean.
New Guinea and the northern parts of New Zealand are part of the Australia plate. The ocean area along southern Asia up to the India plate is also a part of the Australia plate. This plate is small. It includes the central Caribbean countries and runs along the northern edge of South America. This plate includes the northeastern part of the Atlantic ocean, all of Europe, all of Russia except its most eastern part , and down through southeast Asia, including China and Indonesia.
This plate includes the islands that make up the Philipines and north to include parts of southern Japan. It runs along the north western coast of the United States and the southern British Columbia coast. This plate includes all of North America, Greenland, the eastern most part of Russia, northern Japan, and the northwestern part of the Atlantic ocean. It runs from the tip of South America eastwards to form a barrier between the Antarctic plate and the South America plate.
This plate starts at the western edge of South America and stretches east into the southwestern parst of the Atlantic Ocean. This plate moves north and slightly west towards the Caribbean plate and the North America plate. The Blanco, Mendocino, Murray, and Molokai fracture zones are some of the many fracture zones transform faults that scar the ocean floor and offset ridges see text.
The San Andreas is one of the few transform faults exposed on land. The San Andreas fault zone, which is about 1, km long and in places tens of kilometers wide, slices through two thirds of the length of California. Land on the west side of the fault zone on the Pacific Plate is moving in a northwesterly direction relative to the land on the east side of the fault zone on the North American Plate.
Oceanic fracture zones are ocean-floor valleys that horizontally offset spreading ridges; some of these zones are hundreds to thousands of kilometers long and as much as 8 km deep.
Examples of these large scars include the Clarion, Molokai, and Pioneer fracture zones in the Northeast Pacific off the coast of California and Mexico. These zones are presently inactive, but the offsets of the patterns of magnetic striping provide evidence of their previous transform-fault activity.
Not all plate boundaries are as simple as the main types discussed above. In some regions, the boundaries are not well defined because the plate-movement deformation occurring there extends over a broad belt called a plate-boundary zone.
One of these zones marks the Mediterranean-Alpine region between the Eurasian and African Plates, within which several smaller fragments of plates microplates have been recognized. Because plate-boundary zones involve at least two large plates and one or more microplates caught up between them, they tend to have complicated geological structures and earthquake patterns.
We can measure how fast tectonic plates are moving today, but how do scientists know what the rates of plate movement have been over geologic time? The oceans hold one of the key pieces to the puzzle. Because the ocean-floor magnetic striping records the flip-flops in the Earth's magnetic field, scientists, knowing the approximate duration of the reversal, can calculate the average rate of plate movement during a given time span.
These average rates of plate separations can range widely. The Arctic Ridge has the slowest rate less than 2. Evidence of past rates of plate movement also can be obtained from geologic mapping studies. If a rock formation of known age -- with distinctive composition, structure, or fossils -- mapped on one side of a plate boundary can be matched with the same formation on the other side of the boundary, then measuring the distance that the formation has been offset can give an estimate of the average rate of plate motion.
This simple but effective technique has been used to determine the rates of plate motion at divergent boundaries, for example the Mid-Atlantic Ridge, and transform boundaries, such as the San Andreas Fault. Current plate movement can be tracked directly by means of ground-based or space-based geodetic measurements; geodesy is the science of the size and shape of the Earth. Ground-based measurements are taken with conventional but very precise ground-surveying techniques, using laser-electronic instruments.
However, because plate motions are global in scale, they are best measured by satellite-based methods. The late s witnessed the rapid growth of space geodesy, a term applied to space-based techniques for taking precise, repeated measurements of carefully chosen points on the Earth's surface separated by hundreds to thousands of kilometers.
The three most commonly used space-geodetic techniques -- very long baseline interferometry VLBI , satellite laser ranging SLR , and the Global Positioning System GPS -- are based on technologies developed for military and aerospace research, notably radio astronomy and satellite tracking. Among the three techniques, to date the GPS has been the most useful for studying the Earth's crustal movements.
Twenty-one satellites are currently in orbit 20, km above the Earth as part of the NavStar system of the U. Department of Defense. These satellites continuously transmit radio signals back to Earth. To determine its precise position on Earth longitude, latitude, elevation , each GPS ground site must simultaneously receive signals from at least four satellites, recording the exact time and location of each satellite when its signal was received.
By repeatedly measuring distances between specific points, geologists can determine if there has been active movement along faults or between plates. The separations between GPS sites are already being measured regularly around the Pacific basin. By monitoring the interaction between the Pacific Plate and the surrounding, largely continental plates, scientists hope to learn more about the events building up to earthquakes and volcanic eruptions in the circum-Pacific Ring of Fire.
Space-geodetic data have already confirmed that the rates and direction of plate movement, averaged over several years, compare well with rates and direction of plate movement averaged over millions of years.
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