Noisy Mariana Trench

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The ocean is a pretty big place, there are creatures we haven’t seen yet and places that have yet to be explored, even with the amazing amount of technology we have researching the sea floor today. One point of interest has been the Mariana Trench, the deepest part of the Earth’s oceans. The Mariana Trench, at its deepest, runs nearly seven miles beneath the surface of the water.

Researchers wanted to know exactly what goes on that far beneath the ocean’s surface, where light cannot penetrate and sound is muffled. As you can imagine this can be pretty difficult to do without expensive and tough equipment, which is designed to withstand the water and extreme pressure that comes with working so far beneath the ocean. What they found surprised even the most experienced oceanographers.

The researchers put a microphone encased in titanium (to protect it against the severe pressure that far under the water) and sent it to a depth of six miles. The scientists were able to hear the propellers of passing ships on the surface, the sounds of a storm passing overhead, and the calls of whales. Scientists also picked up noises related to nearby earthquakes.

Photo of Deep-ocean hydrophone being brought back onboard USCG Cutter Sequoia following successful recovery after the deployment at Challenger Deep. The white top basket on top of pressure case protects hydrophone element.
Photo of Deep-ocean hydrophone being brought back onboard USCG Cutter Sequoia following successful recovery after the deployment at Challenger Deep. The white top basket on top of pressure case protects hydrophone element. Photo: NOAA and Oregon State University.

This part of the Mariana Trench is known as the Challenger Deep, and it is more than 36,000 feet deep. At this depth scientists didn’t expect that their microphone would pick much up, but the three weeks of recordings they were able to create were clear and captured so much more about life on the bottom of the ocean than they ever thought.

Three dimensional perspective of bathymetry at Challenger Deep, Mariana Trench. Challenger Deep is located along axis of Mariana Trench. Tectonic plates, major faults and seamounts in the area are labeled. Source of image is Center for Coastal and Ocean Mapping - Joint Hydrographic Center
Three dimensional perspective of bathymetry at Challenger Deep, Mariana Trench. Challenger Deep is located along axis of Mariana Trench. Tectonic plates, major faults and seamounts in the area are labeled. Image: Center for Coastal and Ocean Mapping – Joint Hydrographic Center

The scientists worked with the US Coast Guard as well as NOAA to continue research on the impact of audio on marine life. They were seeking to create a base line for noise that existed at the bottom of the ocean to compare it with other recordings taken at various depths around the world.

Listen:

An example of a baleen whale vocalizing just before, and during, the magnitude 5 earthquake:


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Sound of the propeller from a passing ship.

More

Mariana Trench: Seven miles deep, the ocean is still a noisy place.  Oregon State University, March 2, 2016.

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