Magma forms far deeper than geologists previously thought, according to new research results.
A team led by geologist Rajdeep Dasgupta of Rice University put very small samples of peridotite, rock derived from Earth's mantle, under high pressures in a laboratory.
The scientists found that the rock can and does liquify, at least in small amounts, at pressures equivalent to those found as deep as 250 kilometers down in the mantle beneath the ocean floor.
Dasgupta said that this answers several questions about Earth's inner workings.
He is the lead author of a paper that appears today in the journal Nature. The research was funded by the National Science Foundation (NSF).
"The results show that in some parts of the Earth, melting, or magma formation, happens very deep beneath Earth's surface," said geologist Jennifer Wade, a program director in NSF's Division of Earth Sciences, which funded the research.
"It also means that some carbon dioxide and water could come from different sources--and deeper within the Earth--than we believed."
The mantle is the planet's middle layer, a buffer of rock between the crust--the top five miles or so--and the Earth's core.
If one could compress millions of years of observation of the mantle to mere minutes, the mantle would look like a rolling mass of rising and falling material.
This slow but constant churning convection brings materials from deep within the Earth to the surface, and higher, through volcanic eruptions.
The team focused on the mantle beneath the ocean because that's where crust is created and where, Dasgupta said, "the connection between the interior and surface world is established."
Magma rises with convective currents, then cools and spreads out to form ocean-floor crust.
The starting point for melting has long been thought to be at 70 kilometers beneath the seafloor.
That had confoun
|Contact: Cheryl Dybas|
National Science Foundation