February 24 2018
(Newport, Oregon) – A group of researchers – mostly from the Oregon coast area – recently spent a considerable amount of time far from these shores and deeper than most have ever gone. The band of explorers eavesdropped on the famed Mariana Trench, near Micronesia, discovering a cacophony of noises down some 36,000 feet – about seven miles. (Photo: researchers deploy the hydrophone into the trench).
What surprised them was the mish-mash of both natural and man-made sounds, when they expected to hear nearly nothing. Everything from ship traffic, whales to even earthquakes was heard, using a a titanium-encased hydrophone.
The researchers were from Oregon State University, the National Oceanic and Atmospheric Administration and the U.S. Guard, including some connected with the Hatfield Marine Science Center in Newport. For three weeks, the group plunged the hydrophone into the trough known as Challenger Deep, in a project designed to establish a baseline for ambient noise in the deepest parts of the Pacific Ocean. Scientists wanted to know more about human-caused noise down below and if that was growing.
Instead they found a rich sound environment created by nature as well. Robert Dziak, a NOAA research oceanographer and chief scientist on the project, said they thought a place so deep would be nearly silent. Yet they heard the sounds of earthquakes creaking and rumbling close by and far away. Whales moaned and sang. Then a category 4 typhoon created an "overwhelming clamor" overhead. Ship traffic and their propellers made their presence known as well.
Dziak's group recorded a loud magnitude 5.0 earthquake that happened about six miles down, at a point where the hydrophone was actually slightly lower than the quake itself.
"The sound of the typhoon was also dramatic, although the cacophony from big storms tends to be spread out and elevates the overall noise for a period of days," Dziak said.
Oregon-based ocean engineer Haru Matsumoto said getting these initial recordings was not easy. Pressures at the depth of seven miles are incredible, and NOAA's Chris Meinig had to help develop a device that could survive that.
"It is akin to sending a deep-space probe to the outer solar system," Dziak said. "We're sending out a deep-ocean probe to the unknown reaches of inner space."
OSU's Joe Haxel will lead another return to Challenger Deep in 2017, where the researchers will deploy the hydrophone for a longer period of time and attach a deep-ocean camera.
Dziak, Matsumoto and Haxel are affiliated with the Acoustics Program in the NOAA/Pacific Marine Environmental Laboratory and work at OSU's Hatfield Marine Science Center in Newport. The project in Challenger Deep is one of a number of projects in which the U.S. Coast Guard partners with NOAA to sponsor scientific research. More about Oregon Coast Science. Where to stay in this area - Where to eat - Maps and Virtual Tours.
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