By simulating the conditions of temperature and pressure below volcanoes, American scientists debunk hypothesis about the emergence of continents
(updated on 6/5/2023 at 00:48 am)
The continents, large land masses that support all life outside the ocean, as important as they are to us, still don’t have a clear origin for science. Now, a study conducted with crystals may have brought us closer to this discovery.
The research was led by geologists associated with the Smithsonian Museum of Natural History in the United States, and focused on a hypothesis about why the continental crust has less iron and more oxidized material than the oceanic one. A popular explanation for this, which emerged in 2018, is the formation of minerals known as garnet.
The formation of garnet crystals from magma would concentrate iron atoms in them, leaving the remaining material more prone to oxidation. As a result, these portions of the crust would become less dense — and this would place them on top of the oceanic crust at a meeting of tectonic plates. In the article published this Thursday (04) in the journal Science, the scientists overthrow this hypothesis by showing that there would not be enough pressure in the lithosphere for the formation of these crystals.
The researchers Elizabeth Cottrell and Megan Holycross sought to simulate at the High Pressure Laboratory at Cornell University, in the United States, the conditions of pressure and temperature in the Earth’s crust that would generate the theorized crystallization. 13 different experiments were conducted, with pressures ranging from 15,000 to 30,000 times atmospheric pressure and temperatures from 950 to 1,230 ºC.
The rates of iron assimilated in the formed crystals were then compared with those of garnet samples from the collection of various geological institutions around the world. The result indicated that, under the tested conditions — calibrated to exactly simulate the behavior below volcanoes — the removal of iron from the magma would not be enough to explain the level of this element in the continental crust today.
The research is a classic example of how science progresses even if the results when the results are positive — by not getting garnet samples with the expected iron concentration, the experiments allowed a theory to be proven false.
The results still leave open the question of how the continents emerged. The most likely hypothesis from now on, that sulfur also played a role in crustal oxidation, will be investigated by future research by other scientists at the same institution.
Source: Science Via: Phys.org
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