Earth’s upper mantle is 60°C warmer than scientists thought, new study finds. This discovery will make it possible to model more precisely the many geodynamic processes of the Earth, including plate tectonics.
The upper layer of the Earth’s mantle (or the asthenosphere) is actually at a higher temperature than previously thought. » Having such a warm mantle could mean that the mantle is less viscous, which who could explain how tectonic plates are in measure of move to-above the asthenosphere said study lead researcher Emily Sarafian, of MIT’s Geology and Geophysics program.
The expert compares the effect of temperatures on the asthenosphere to that of temperatures on honey. » If you put the honey in the fridge for an hour, it will barely be able to flow when you take it out. “, she explains to the review LiveScience. » If instead you put it on the stove, it will sink very easily, because it will be hotter « .
Many clues show that this mantle is warmer, but for obvious reasons, scientists cannot go there and measure temperatures directly. Instead, they recreate mantle rocks in the lab.
» Once they have a synthetic mantle rock, they subject it to different pressures and temperatures to determine the temperature at which the rock melts at a given pressure. “says the researcher. » By increasing the temperature in small intervals and at different pressures, scientists can note exactly when their rock is melting. « .
Only there is one problem: water. Indeed, the rocks of the mantle contain a small amount of water, but it is very difficult to determine it and therefore to have the right amount in the laboratory samples. Moreover, the atmosphere also contains water and plays on the process.
It is a mineral, olivine, which then came to the aid of the researchers to solve the enigma in another way. It is found naturally in the rock of the Earth’s mantle and it comes in the form of grains as fine as grains of sand, but large enough for researchers to measure the amounts of water.
» We have carried out fusion experiments the same way as the previous scientists have done it, in putting high pressure synthetic rock and temperatures, but adding these grains to our experiments. Ideally, the sample ended up having the same amount of water as the coat “, she adds.
Their results suggested that the envelope melts when it is relatively close to the Earth’s surface. » This should mean that the previous estimate of the mantle temperature was too low and that the mantle is 60°C warmer concluded Sarafian in the study published in the journal Science. » This is a very important difference! »