Kazimiera
02-27-2013, 01:02 AM
Earth's Deepest Spot Revealed in Unprecedented Detail
Sound waves have allowed scientists to peer through the dark ocean depths and create a new map of the deepest spot in the oceans: the Challenger Deep in the Mariana Trench.
http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Marianatrenchmap.png/300px-Marianatrenchmap.png
The new map has a resolution of 100 meters (about 330 feet) per pixel, nearly 20 times more detailed and precise than previous efforts.
Researchers from the Center for Coastal and Ocean Mapping/Joint Hydrographic Center at the University of New Hampshire used what are called multibeam echo sounders to map the Mariana Trench from August to October 2010.
The Mariana Trench stretches 2,500 kilometers (1,500 miles) in an arc that is edged by islands such as Guam and Saipan. Its deepest point is known as the Challenger Deep, some 35,756 feet (10,890 meters) — or nearly 7 miles (11 kilometers) — beneath the surface of the sea. The trench is deeper than Mount Everest is tall.
"Titanic" director James Cameron dove down into the Challenger Deep on March 26, only the second time in history man has visited the place. The dive took two hours and 36 minutes and has renewed interest in the exploration of the deep ocean. The first — and until Cameron, only — trip to this spot was made on Jan. 23, 1960, in a submersible called the Trieste.
The new map of the trench shows depths in a series of shades of blue, with the darkest blues representing the deepest depths. Nearly 154,000 square miles (400,000 square km) of seafloor were surveyed by the oceanographers to make the map.
The multibeam echo sounders were mounted to the hulls of ships, from where they sent out pulses of sound waves toward the seafloor and then recorded the reflections. The longer the reflection took to come back to the instrument, the deeper the section of seafloor it bounced off of.
The sounders send out the pulses in a fan shape, allowing for the construction of 3D maps.
http://www.ouramazingplanet.com/images/i/4716/i02/mariana-trench.jpg?1334593078
The new mapping effort also found four deep-water "bridges" crossing the trench and standing as much as 8,200 feet (2,500 m) above the trench floor. These bridges were once seamounts (mountains on the ocean floor that don't reach the water's surface) that were carried across the ocean floor by the spreading of the plates on which they sit. As plates (in this case the Pacific and Philippine plates) converge, some of the seamounts collide with features on the opposite trench, creating the bridges.
http://www.ouramazingplanet.com/2773-mariana-trench-map.html
Depth of Challenger Deep
http://technabob.com/blog/wp-content/uploads/2012/03/challenger_deep.jpg
Seafloor "Bridges" Found to Span Earth's Deepest Trench
The Mariana Trench, located in the Pacific Ocean off the eastern coasts of Japan and the Philippines — at a depth of around 6.8 miles (11 kilometers) below sea level — is famous for being the deepest point on the planet's surface.
Now, to add to the Mariana Trench's fame, marine geophysicists recently mapped a set of surprising seafloor features nearby. At least four underwater "bridges" span the depths of the trench, where the Pacific Plate dives under the Philippine Plate.
"It wasn't common knowledge that these bridges occurred at all," said James Gardner, a marine geophysicist at the University of New Hampshire who found the structures. "This is really the first time they've been mapped in any detail."
Bridging the trench
As the Pacific and Philippine tectonic plates converge, they carry seamounts (mountains on the ocean floor that don't reach the water's surface) and other underwater features with them toward the trench itself. Some of these plow into other structures on the opposite side of the trench — in a sort of slow-motion seamount collision — or into the trench wall itself.
The result is an underwater "bridge" that stretches across the Mariana Trench. Gardner and a colleague found four of these structures, some rising as high as 6,600 feet (2,000 meters) above the trench and measuring up to 47 miles (75 km) long.
The largest of the four, Dutton Ridge, was mapped in low resolution in the 1980s, but scientists hadn't noticed any other similar structures in the area. Because the seafloor in the region is riddled with seamounts, guyots (flat-topped seamounts) and other features — many of them part of the Magellan Seamount chain — Gardner suspected he could find other bridges.
"As the Pacific Plate gets thrust down underneath the Philippine Plate, it wouldn't be totally unexpected that you'd find these things bridging across the trench and being accreted to the inner wall," Gardner told OurAmazingPlanet.
Using a multibeam echosounder (a tool that uses sonar to measure the topography of the ocean floor in detail), Gardner and a colleague mapped a large swath of the ocean floor surrounding the trench. They presented their findings at the December meeting of the American Geophysical Union in San Francisco.
Deep, cold and creeping slowly
What the bridges mean for the ocean floor and its occupants is unclear, Gardner said.
"I would certainly expect Dutton Ridge and the others to have different fauna and flora than the trench floor, because they stand about 2 kilometers [1.2 miles] higher,” Gardner said. "But the extreme depth would make it hard to monitor the biology or seafloor currents in the area."
In fact, the pressure at the bottom of the Mariana Trench is more than eight tons per square inch, and water temperatures hover just above freezing, making it a challenging environment for researchers and sea life alike.
The long-term fate of the bridges is also unknown, Gardner said.
Dutton Ridge, the northernmost of the four bridges, has settled in over the Mariana Trench and seems to be "choking" the plate boundary for now, Gardner said. He also found evidence suggesting that the trench may have already swallowed up other similar bridges.
Whether and when Dutton Ridge and the other three bridges will plunge to the same end isn't clear. And with the Pacific and Philippine plates creeping steadily toward each other at a rate of less than an inch (2 cm) per year, we aren't likely to find out anytime soon.
http://www.ouramazingplanet.com/2197-seafloor-bridges-span-deepest-ocean-trench.html
http://www.thedivesite.co.za/files/1/images/_57087494_challenger_deep_trench_624.jpg
http://2.bp.blogspot.com/-_u3bIndAvxk/T06AIhWKe3I/AAAAAAAAAeA/NiExOY7-ET0/s1600/mariana-trench-diagram-story-top.jpg
Sound waves have allowed scientists to peer through the dark ocean depths and create a new map of the deepest spot in the oceans: the Challenger Deep in the Mariana Trench.
http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Marianatrenchmap.png/300px-Marianatrenchmap.png
The new map has a resolution of 100 meters (about 330 feet) per pixel, nearly 20 times more detailed and precise than previous efforts.
Researchers from the Center for Coastal and Ocean Mapping/Joint Hydrographic Center at the University of New Hampshire used what are called multibeam echo sounders to map the Mariana Trench from August to October 2010.
The Mariana Trench stretches 2,500 kilometers (1,500 miles) in an arc that is edged by islands such as Guam and Saipan. Its deepest point is known as the Challenger Deep, some 35,756 feet (10,890 meters) — or nearly 7 miles (11 kilometers) — beneath the surface of the sea. The trench is deeper than Mount Everest is tall.
"Titanic" director James Cameron dove down into the Challenger Deep on March 26, only the second time in history man has visited the place. The dive took two hours and 36 minutes and has renewed interest in the exploration of the deep ocean. The first — and until Cameron, only — trip to this spot was made on Jan. 23, 1960, in a submersible called the Trieste.
The new map of the trench shows depths in a series of shades of blue, with the darkest blues representing the deepest depths. Nearly 154,000 square miles (400,000 square km) of seafloor were surveyed by the oceanographers to make the map.
The multibeam echo sounders were mounted to the hulls of ships, from where they sent out pulses of sound waves toward the seafloor and then recorded the reflections. The longer the reflection took to come back to the instrument, the deeper the section of seafloor it bounced off of.
The sounders send out the pulses in a fan shape, allowing for the construction of 3D maps.
http://www.ouramazingplanet.com/images/i/4716/i02/mariana-trench.jpg?1334593078
The new mapping effort also found four deep-water "bridges" crossing the trench and standing as much as 8,200 feet (2,500 m) above the trench floor. These bridges were once seamounts (mountains on the ocean floor that don't reach the water's surface) that were carried across the ocean floor by the spreading of the plates on which they sit. As plates (in this case the Pacific and Philippine plates) converge, some of the seamounts collide with features on the opposite trench, creating the bridges.
http://www.ouramazingplanet.com/2773-mariana-trench-map.html
Depth of Challenger Deep
http://technabob.com/blog/wp-content/uploads/2012/03/challenger_deep.jpg
Seafloor "Bridges" Found to Span Earth's Deepest Trench
The Mariana Trench, located in the Pacific Ocean off the eastern coasts of Japan and the Philippines — at a depth of around 6.8 miles (11 kilometers) below sea level — is famous for being the deepest point on the planet's surface.
Now, to add to the Mariana Trench's fame, marine geophysicists recently mapped a set of surprising seafloor features nearby. At least four underwater "bridges" span the depths of the trench, where the Pacific Plate dives under the Philippine Plate.
"It wasn't common knowledge that these bridges occurred at all," said James Gardner, a marine geophysicist at the University of New Hampshire who found the structures. "This is really the first time they've been mapped in any detail."
Bridging the trench
As the Pacific and Philippine tectonic plates converge, they carry seamounts (mountains on the ocean floor that don't reach the water's surface) and other underwater features with them toward the trench itself. Some of these plow into other structures on the opposite side of the trench — in a sort of slow-motion seamount collision — or into the trench wall itself.
The result is an underwater "bridge" that stretches across the Mariana Trench. Gardner and a colleague found four of these structures, some rising as high as 6,600 feet (2,000 meters) above the trench and measuring up to 47 miles (75 km) long.
The largest of the four, Dutton Ridge, was mapped in low resolution in the 1980s, but scientists hadn't noticed any other similar structures in the area. Because the seafloor in the region is riddled with seamounts, guyots (flat-topped seamounts) and other features — many of them part of the Magellan Seamount chain — Gardner suspected he could find other bridges.
"As the Pacific Plate gets thrust down underneath the Philippine Plate, it wouldn't be totally unexpected that you'd find these things bridging across the trench and being accreted to the inner wall," Gardner told OurAmazingPlanet.
Using a multibeam echosounder (a tool that uses sonar to measure the topography of the ocean floor in detail), Gardner and a colleague mapped a large swath of the ocean floor surrounding the trench. They presented their findings at the December meeting of the American Geophysical Union in San Francisco.
Deep, cold and creeping slowly
What the bridges mean for the ocean floor and its occupants is unclear, Gardner said.
"I would certainly expect Dutton Ridge and the others to have different fauna and flora than the trench floor, because they stand about 2 kilometers [1.2 miles] higher,” Gardner said. "But the extreme depth would make it hard to monitor the biology or seafloor currents in the area."
In fact, the pressure at the bottom of the Mariana Trench is more than eight tons per square inch, and water temperatures hover just above freezing, making it a challenging environment for researchers and sea life alike.
The long-term fate of the bridges is also unknown, Gardner said.
Dutton Ridge, the northernmost of the four bridges, has settled in over the Mariana Trench and seems to be "choking" the plate boundary for now, Gardner said. He also found evidence suggesting that the trench may have already swallowed up other similar bridges.
Whether and when Dutton Ridge and the other three bridges will plunge to the same end isn't clear. And with the Pacific and Philippine plates creeping steadily toward each other at a rate of less than an inch (2 cm) per year, we aren't likely to find out anytime soon.
http://www.ouramazingplanet.com/2197-seafloor-bridges-span-deepest-ocean-trench.html
http://www.thedivesite.co.za/files/1/images/_57087494_challenger_deep_trench_624.jpg
http://2.bp.blogspot.com/-_u3bIndAvxk/T06AIhWKe3I/AAAAAAAAAeA/NiExOY7-ET0/s1600/mariana-trench-diagram-story-top.jpg