“Diamonds form in fluids,” Wagner explained. “If diamonds are there, fluids are there.” Searching for evidence of water in Earth’s deep interiorĭiamonds contain pieces of minerals that the researchers sampled to confirm the presence of fluids. These studies showed that water released from minerals weakens the rock around the fault and allows slabs of rock to slip.īut scientists were not convinced that this could explain deep-focus earthquakes due to the notion that fluids couldn’t make it far enough down into the planet’s interior. Wagner and her colleagues challenged this notion in their study, noting that some rare diamonds originate in the same depths as deep-focus earthquakes. The water they hold get squeezed out of them so that the rocks appear to sweat.Īt the same time, studies suggested that water trapped underground plays a part in setting off intermediate-depth earthquakes, which occur between 45 to 185 miles beneath the ground. These are bright, blue rocks formed under high temperatures and pressures in the Earth’s mantle. Instead, all the water deep in the Earth is trapped inside rocks called ringwoodites. This reservoir is three times the volume of what is found on the surface but is not an actual underground sea. Recent research found that a reservoir of water lurks more than 400 miles beneath the surface. “Once you get a few tens of kilometers down, it becomes incredibly difficult to explain how we are getting slip on a fault when the friction is so incredibly high,” Wagner added. The extreme temperatures also enhance the ability of rocks to deform and accommodate changing stresses. When enough stress has accumulated, it causes this pair of rocks to suddenly slip and slide past each other, triggering earthquakes.īut intense pressures deep in the Earth create too much friction for this sliding to occur. Usually, earthquakes occur near the surface after stress builds up between two blocks of rock. “The big problem that seismologists have faced is how it’s possible that we have these deep-focus earthquakes at all,” said co-author Lara Wagner. First detected in the 1920s, these earthquakes continue to confound scientists to this day. What causes deep-focus earthquakes?ĭeep-focus earthquakes are earthquakes that occur between 185 and 435 miles below the Earth’s surface. The researchers detailed their findings in a paper published May 26 in the journal AGU Advances. A massive “ocean” hidden in the Earth’s mantle may be triggering earthquakes that originate deep in the planet’s interior. This is what researchers from Carnegie Institute for Science and University of Alberta in Canada suggest in their study, which links fluids trapped in rocks deep underground to so-called deep-focus earthquakes.
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