A network of devices called MERMAIDs is taking seismographs where they've never been.
- Most of the ocean floor is inaccessible to seismologists.
- Much can be learned about the interior of Earth by listening to earthquakes.
- Ingenious new floating sensors are changing the ocean seismology game.
9 MERMAIDs floating free<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE1MTg4Ny9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTQ3Mjc3OH0.HgCHRyjqODfm9J9oJHD5FppzIjTHgohkCBSxwHEt2JM/img.jpg?width=980" id="b55d8" class="rm-shortcode" data-rm-shortcode-id="c430ce78d4c1c7b09dfb7711caf0134d" data-rm-shortcode-name="rebelmouse-image" />
Image source: Yann Hello, University of Nice<p>The MERMAID project is the brainchild of Princeton geoscientist Frederik Simons. "Imagine a radiologist forced to work with a CAT scanner that is missing two-thirds of its necessary sensors," he tells <a href="https://phys.org/news/2019-02-mermaids-reveal-secrets-ocean-floor.html" target="_blank" data-vivaldi-spatnav-clickable="1">Phys.org</a>. He and colleague Guust Nolet have been developing their system for 15 years.</p><p>Each "MERMAID" is a floating <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ocean-bottom-seismometer" target="_blank" data-vivaldi-spatnav-clickable="1">seismometer/hydrophone</a> set free to drift where it will, and together they form a seismographic network. "MERMAID" stands for "Mobile Earthquake Recording in Marine Areas by Independent Divers."</p><p>They generally float at a depth of 1,500 meters. But when they pick up audio that may signify the start of an earthquake, they rise to the surface, taking no longer than 95 minutes to get there, poke their heads out of the water to acquire their location via GPS, and transmit the data they've collected.<span></span></p><p>The nine MERMAIDs have just completed their first two-year tour of duty.</p>
What the MERMAIDs found<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE1MTkxNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNjA5NTk3Mn0.sXU4J7iS1ug428FmTMEjN7F7ICQalxquPNuqyqG7GyA/img.jpg?width=980" id="a33fa" class="rm-shortcode" data-rm-shortcode-id="4c5c933a04cef94f927f8c5df32a5eab" data-rm-shortcode-name="rebelmouse-image" />
This shows the speed of seismic waves moving through the Earth from the surface at the top of the cross-section down to about 2,890 km deep at its bottom edge. Darker colors signify slower wave movement. Image source: Princeton University<p>The MERMAIDs drifted through an area ranging from about 20° north to 20° south centered on the Galápagos Islands. Their data revealed the volcanoes on the islands are fed hot rock via a narrow conduit that extends downward to about 1,200 miles (1,900 km). Such a deep ocean "mantle plume," a phrase coined by geophysicist W. Jason Morgan, who hypothesized their existence in 1971, has never been imaged in detail prior to the deployment of the MERMAIDs.</p><p>The high temperatures they recorded is of special interest. Ever since observations have contradicted Lord Kelvin's 19th-century proposal that the Earth should be cooling quickly, scientists have wondered why the Earth has somehow managed to remain at a fairly constant temperature instead. The new research suggests an answer. </p><p>In a Princeton University press release, Nolet explained: </p><p style="margin-left: 20px;">"These results of the Galápagos experiment point to an alternative explanation: the lower mantle may well resist convection, and instead only bring heat to the surface in the form of mantle plumes such as the ones creating Galápagos and Hawaii."</p><p>Next up is a new fleet of some 50 MERMAIDs to be released in the South Pacific with the aim of learning more about the plume region beneath Tahiti. That project will be led by <a href="http://www.sustc.edu.cn/en/faculty_finder/f/Chen%20Yongshun" target="_blank" data-vivaldi-spatnav-clickable="1">Chen Yongshun</a> of Southern University of Science and Technology, who enthuses, "Stay tuned! There are many more discoveries to come."</p>
The clash of tectonic plates beneath us is just part of life on Earth—unless, of course, there is human interference like in the American Midwest.
Earthquakes are usually pretty scary, but they are a natural part of life on Earth. The reason they are devastating to humans is because we have built buildings and cities on top of ground that is often not as stable as we'd like it to be. And here's an important perspective: "Earthquakes don’t kill people, buildings do," says Bill Nye, as he explains what causes this geological phenomenon. Beneath the oceans' water, our planet has big slabs of land called tectonic plates that sit atop the earth's lava (a layer of molten rock that scientist call magma). There are gaps between these tectonic plates, so they slide and move over the magma and at times collide, causing a natural earthquake. But there are also manmade earthquakes, like the ones in the American Midwest. Bill Nye explains what's going on with these quakes, the basics of what to do if you're ever in an earthquake, and how science and smarter architecture can help humans survive the clashing of these tectonic plates beneath us. Bill Nye is the author of Unstoppable: Harnessing Science to Change the World.