Surprising new study finds that the mantle is hotter than we thought

meltingtempe

Researchers from the Woods Hole Oceanographic Intuition (WHOI) discovered that upper parts of Earth’s mantle may be hotter than we previously thought

A new study led by Woods Hole Oceanographic Institution (WHOI) suggests the mantle—the mostly solid, rocky part of Earth’s interior that lies between its super-heated core and its outer crustal layer—may be hotter than previously believed. The new finding, published March 3 in the journal Science, could change how scientists think about many issues in Earth science including how ocean basins form.

“At mid-ocean ridges, the tectonic plates that form the seafloor gradually spread apart,” said the study’s lead author Emily Sarafian, a graduate student in the MIT-WHOI Joint Program. “Rock from the upper mantle slowly rises to fill the void between the plates, melting as the pressure decreases, then cooling and re-solidifying to form new crust along the ocean bottom. We wanted to be able to model this process, so we needed to know the temperature at which rising mantle rock starts to melt.”

But determining that temperature isn’t easy. Since it’s not possible to measure the mantle’s temperature directly, geologists have to estimate it through laboratory experiments that simulate the high pressures and temperatures inside the Earth.

Water is a critical component of the equation: the more water (or hydrogen) in rock, the lower the temperature at which it will melt. The peridotite rock that makes up the upper mantle is known to contain a small amount of water. “But we don’t know specifically how the addition of water changes this melting point,” said Sarafian’s advisor, WHOI geochemist Glenn Gaetani. “So there’s still a lot of uncertainty.”

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