A new analysis finds surprisingly cool temperatures at volcanic hotspots.
Scientists have long thought that these islands were fueled by thermal plumes welling up from deep within the Earth’s mantle. However, when researchers compared the temperatures of volcanic hotspots and mid-ocean ridges around the world, they found that many of these so-called hotspots were actually rather cool.
The temperature of mid-ocean ridges should represent typical temperatures within the mantle, she says. In order to upwell, a plume must be somewhere between 100 to 150 degrees Celsius hotter than the surrounding rock. “They have to be hotter to be able to rise through the entire mantle, and therefore hotter than the mid-ocean ridge,” Lithgow-Bertelloni says.
The researchers used a model that drew upon seismic measurements from around the globe to infer the temperature at all 46 known oceanic hotspots. The team also calculated that the average temperature at mid-ocean ridges was roughly 1,388 degrees Celsius . The toastiest cluster of hotspots included the volcanoes of Iceland, Samoa, Galápagos, and Hawaii. Warm hotspots were found at Bermuda and the Canary Islands, while cold hotspots were found at Cameroon, Ascension Island, and the Great Meteor, or New England, hotspot in the North Atlantic.