Volcano

Earth’s mantle may be hotter than thought

Earth's mantle
HOT STUFF Temperatures in Earth’s mantle are higher than previously thought, results from a new experiment suggest.

Temperatures across Earth’s mantle are about 60 degrees Celsius higher than previously thought, a new experiment suggests. Such toasty temperatures would make the mantle runnier than earlier research suggested, a development that could help explain the details of how tectonic plates glide on top of the mantle, geophysicists report in the March 3 Science.

“Scientists have been arguing over the mantle temperature for decades,” says study coauthor Emily Sarafian, a geophysicist at the Woods Hole Oceanographic Institution in Massachusetts and at MIT. “Scientists will argue over 10 degree changes, so changing it by 60 degrees is quite a large jump.”

The mostly solid mantle sits between Earth’s crust and core and makes up around 84 percent of Earth’s volume. Heat from the mantle fuels volcanic eruptions and drives plate tectonics, but taking the mantle’s temperature is trickier than dropping a thermometer down a hole.

Scientists know from the paths of earthquake waves and from measures of how electrical charge moves through Earth that a boundary in the mantle exists a few dozen kilometers below Earth’s surface. Above that boundary, mantle rock can begin melting on its way up to the surface. By mimicking the extreme conditions in the deep Earth — squeezing and heating bits of mantle that erupt from undersea volcanoes or similar rocks synthesized in the lab — scientist can also determine the melting temperature of mantle rock. Using these two facts, scientists have estimated that temperatures at the boundary depth below Earth’s oceans are around 1314° C to…

Harnessing Volcano Energy

When we say a volcano is dormant, that doesn’t mean that it’s dead; it just means that it hasn’t erupted in some time. Iceland has more than its fair share of volcanos, and the nation is treating those volcanos as a national resource. A resource of thermal energy that is. The volcano under Reykjanes Peninsula hasn’t erupted in over 700 years, but it will soon contribute to Iceland’s energy output. A group of scientists and engineers dug a hole almost three miles deep toward the volcano’s thermal core.

At this depth, the hole does not enter the magma chamber but does penetrate the rock surrounding it, which the researchers measured…

3 Mountains Taller Than Everest

by James Hunt

At almost 30,000 feet, Mount Everest may seem like it’s as tall and as high a mountain as has ever existed. But the title of Tallest Mountain all depends on how—and where—you make your measurements. Here are three competitors.

1. MAUNA KEA

The dormant volcano Mauna Kea in Hawaii is one of several known peaks that are arguably taller than Everest—as long as you’re willing to award the title of “tallest” based on a technicality.

Certainly, the highest point of Mauna Kea is definitely not higher than Everest’s. At 4205 meters (13,796 feet) above sea level, it’s less than half as high as Everest. So why is it such a good challenger for the accolade of tallest mountain? It all hinges on those three simple words: “above sea level.”

If you discard the water that surrounds Mauna Kea and measure the mountain from its underwater base—a measurement strangely called the “dry prominence,” or the solid bottom of all features—Mauna Kea is taller than Everest by almost 500 meters (1640 feet). Starting at the point where Mauna Kea begins to rise out of the surrounding crust, the mountain has a total height of around 9330 meters (30,610 feet). Since no part of Everest is submerged, its dry prominence is the same as its height above sea level. But if you could place the two mountains side-by-side, on a flat plane, Mauna Kea would indisputably be the taller of the two.

There are several factors that enable Mauna Kea to be taller than a mountain formed above sea level, but the main reasons are to do with the crust beneath it. Oceanic crust is denser than continental crust and therefore less prone to sag. It’s also a lot thinner than continental crust—about 4 to 6 miles thick, rather than 15 to 43 miles like continental crust.

By comparison, Everest has the heavy weight of a mountain sitting on top of the already heavy weight of continental crust. Since water is much less dense than rock, the oceanic crust below Mauna Kea is carrying less weight beneath sea level than the continental crust beneath Mount Everest. It can therefore support a higher prominence than would be possible above…