A new theory of the formation of the ancient continents Facts
The structure of the Earth can be compared with oranges: its bark like skin, covered with a thick mantle. By its parameters bark 30-40 kilometers deep, and be looser than the thinner oceanic crust.
"According to the new theory, the first continental crust formed when tectonic plates collide, plunging oceanic crust into the Earth's mantle. There is partially melted at the approximate depth of 100 kilometers. This molten rock and formed the first continent, "- said study author Thorsten Nigel, professor at the Institute of Geosciences Steinmann in Bonn. The theory explains the formation of the oldest continental rocks (3.8 billion years ago) found in western Greenland.
The composition of the continental crust for a version of the proposed semi-oceanic crustal rocks, melted by 10-30%. Unfortunately, the concentrations of the main chemical components in the re-solidified breed does not allow us to estimate the depth at which there was a meltdown. To answer this question, we need to know what the remaining 70-90% of the rock was oceanic crust. Researchers from Bonn also analyzed for the presence of trace species found in varying concentrations. Scientists are confident that with their help, they will be able to determine the residual rock minerals that were present in the molten rock at depth.
Before magma separated from the bedrock, between viscous and hard rock minerals, trace elements were exchanged. Different minerals have their own special ways of separation, when the minerals begin to melt. In other words, the concentration of trace elements in molten rocks indicates the residual elements of the bedrock. This, in turn, allows scientists to reconstruct the structure of a possible bedrock and the depth at which there was the continental crust.
The scientists were able to reconstruct a computer model of the underlying and the molten rock, which may have resulted from partial melting of the oceanic crust at different depths and at different temperatures. These data were compared with the actual level of concentration of trace elements in ancient rocks. It was found that the formation of molten rock, which later emerged the ancient continents, oceanic crust does not fall below 100 kilometers. Rather, this depth is not more than 30-40 kilometers.