Rumbles From the Deep
If a hydrothermal vent in the deep ocean makes a sound, does anyone hear it?
Until recently, many scientists would have answered that question with a "no." Scientists in the 1980's had attempted to record vent sounds but they did not detect a signal. It had generally been believed that the hot fluids streaming from deep-sea hydrothermal vents don't generate detectable noise. But a few scientists at the University of Washington (UW) decided to give vents a closer listen, using recent technology, and they got an earful.
Some of the largest vents on the seafloor, known as black smokers, release hot fluids into the surrounding water at rates of up to 19 liters (5 gallons) a second—twice as fast as the average fire hose. Tim Crone, a graduate student at UW, found it difficult to believe that fluid moving this violently wouldn't make some noise in the surrounding environment - even very deep in the ocean.
Using a deep-sea underwater sound recorder, Crone and his colleagues recorded over 180 hours of sound at two different vents located 2200 meters (7,150 feet) below the ocean's surface. Known as "Sully" and "Puffer", the two vents are part of the Juan de Fuca Ridge, an area about 300 miles west of Seattle, Washington. The ridge is an area where the seafloor spreads apart in opposite directions and new crust is formed by occasional volcanic eruptions.
To the surprise of Crone, the recordings revealed not only that the vents make sound, but also that the sound was louder than anyone expected. The low rumbling noise of the vents is thought to be caused as the hot fluids pulse and rush through the chimney that surrounds the vent opening, and then cool and mix with the surrounding cold water.
Sure, it's interesting to know that vents make sound, but what important information can vent sounds communicate to scientists who study these unique ecosystems?
According to Crone, studying the patterns of vent sounds can help uncover how the fluids flowing out of the vents change over time, and what forces might cause these changes. So far, they have learned that the rumbling of the vents increases or decreases along with the rise and fall of the tides. Listening to the changes in sound may also help scientists better understand earthquakes and volcanic eruptions that occur on the seafloor.
It has been suggested that deep-sea animals may benefit from vent sounds, too. Fish and other animals may be able to detect and use the sound vibrations to locate vents for a home or a meal, or to avoid the super-heated fluids and toxic chemicals that the vents release.
Right now, vents around the world are telling stories of how the Earth gives birth—all we have to do is listen.