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UNH scientists explore, map world’s deepest point off Guam’s coast

Staff Writer

Published: Monday, February 13, 2012

Updated: Monday, February 13, 2012 23:02

The Mariana Trench, located off the coast of Guam, is the deepest known place on earth. At approximately 36,000 feet deep at its deepest point, the trench could easily house Mount Everest, with over a mile of depth to spare.

University of New Hampshire scientists have not let these measurements prevent them from exploring the region. On the contrary, researchers have mapped the entirety of the trench - 400,000 square feet, according to a recent press release - and discovered four "bridges." Unprecedented depth measurements were recorded as well.  

Researchers from the UNH Center for Coastal and Ocean Mapping/UNH-NOAA Joint Hydrographic Center mapped the western Pacific region over the course of several months in 2010. UNH professors James Gardner and Andrew Armstrong led the mission, and also presented the expedition's findings at the recent and prestigious American Geophysical Union meeting.

Earlier satellite images suggested the possibility of the existence of one bridge, but certainly not four.

"There is nothing significant about four bridges, rather than one," Gardner said. "The significant point is that there are bridges at all."

The finding of the bridges can be attributed to improved data resolution. Prior to this endeavor, the only available resolution was about two kilometers per depth point, whereas Gardner's data had a resolution of 100 meters per depth point, or about 20 times the detail.

The scientists used an advanced piece of equipment called a multi-beam echosounder to gather information.

"A multi-beam echosounder sends out a pulse of sound directed at the seafloor and then records the time for an echo to return from the seafloor. The listening part of the system is divided into several hundred narrow listening receivers, each pointed at a different angle to either side of the vertical. … This provides us with a ‘swath' of depth measurements," Gardner said.

The scientist and professor compared the process to mowing the grass with a lawn mower; the equipment goes back and forth, covering 100 percent of the seafloor.

The bridges that, according to Discovery News, rise more than 8,000 feet above the seafloor were created due to the collision of the northwest-shifting Pacific and the eastern-shifting Philippine Plates. The older, and thus colder and denser Pacific Plate dove under or "subducted" the Philippine Plate, and carried its ridges and seamounts along with it. Once these features descended into the trench, they attached to the western wall and have not since been broken up; these intact segments form the bridges.  

These bridges were not the only discovery, as the depth was also recalculated. Before, the deepest point, Challenger Deep (named for the British ship that pinpointed the deep water in 1951) was thought to be between 35,767 and 35,813 feet; new measurements report a depth of between 35,938 and 36,200 feet.

UNH scientists have traveled to the area four times, and trench expeditions are gaining momentum across the globe. The race is on to learn more about the deepest, darkest and, according to the Mariana Trench National Wildlife Refuge, the oldest geographical seafloor of any ocean.

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