Geologists Accidentally Found a Ghost Plume Rising From Earth's Mantle
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Mantle plumes are important geologic processes—they interact with plate tectonics, create rich mineral deposits, and even contribute to mass extinction events.
Now, a new study has found evidence of a 'ghost plume'—a mantle plume that shows no sign of volcanic activity on the surface—under eastern Oman.
Understanding these ghost plumes, and especially developing ways to find more of them, will help geologists better understand how much heat is escaping the core-mantle boundary.
Mantle plumes are one of the most dynamic geologic processes on Earth. As their name suggests, these plumes move hot rock near the core-mantle boundary toward the surface, creating new landmasses (such as Hawai'i) or causing powerful geothermal activity (Yellowstone). Of course, moving all that magma beneath the Earth comes with a healthy dose of volcanism for those who live above these mantle superhighways—unless you live in Oman, that is.
In a new paper published in the journal Earth and Planetary Science Letters, an international team of scientists—led by seismologist Simone Pilia of King Fahd University of Petroleum and Minerals in Saudi Arabia—claims to have found an amagmatic mantle plume, also known as a 'ghost plume,' resting beneath eastern Oman. Speaking with New Scientist, Pilia said that he accidentally discovered the plume while analyzing seismic data from the region.
Seismologists typically analyze the interior of Earth using earthquake data from around the world. When an earthquake occurs, it sends seismic waves through the planet, and the trajectory of those waves can give scientists insight into the interior of the globe. While analyzing some of these waves, Pilia noticed a cylindrical area beneath eastern Oman where they moved more slowly and the rock they moved through appeared to be less rigid. This means that temperatures were much higher in this region, indicating the presence of a mantle plume. But eastern Oman doesn't display the surface volcanism that's typical of such areas.
Taking a closer look with independent measurements, Pilia confirmed that a mantle plume—nicknamed 'Dani' after his son—likely existed roughly 660 kilometers below the surface. 'The more we gathered evidence, the more we were convinced that it is a plume,' Pilia told New Scientist.
Although there is no volcanic activity on the surface above this plume, there are other pieces of evidence that point to some sort of geologic anomaly in the region. For example, Oman continues to rise in elevation long after the impacts of tectonic compression—a process that squeezes the Earth's crust together. The plume's existence also fits nicely into models detailing the movement of the Indian tectonic plate during the late Eocene.
If this 'Dani plume' truly is a ghost plume, it would be the first one ever detected, and could possibly lead scientists to re-examine just how much heat is moving from the core-mantle boundary—especially if more ghost plumes exist around the world. Not only could that change Earth's geologic history, but mantle plumes provide many real-world benefits. They initiating seafloor spreading; they serve as sources of large nickel, platinum, and diamond deposits; and they can even cause global mass extinction events.
If a variety of 'ghost plumes' are also at work around the world, it's important that we learn as much as we can.
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