– The tectonic movement of plates on Earth could be caused by the collision of our planet with a giant meteorite. According to scientists from Australia, is one of the probable causes, writes N+1 with reference to Nature Geoscience.
Modern tectonic movement of plates on Earth is characterized by several features. This, for example, continuous updating of the oceanic crust due to the formation of new igneous rocks at mid-ocean ridges and slow absorption of the crust in subduction zones (long linear area along which there is a dip of some crustal blocks under the other – if). Such processes lead to a complete upgrade of the crust about 100 million years. When and for what reasons a movement of the earth’s crust by this mechanism is still an open question.
It is known that subduction zones are not less than 3 billion years, but what happened to the plates in cataractous era (covers the first 600 million years of Earth’s history) is unknown. Sedimentary rocks from kataria almost gone, so the analysis of geological events that took place earlier than 4 billion years ago, extremely difficult. For this purpose, the analysis of clastic rocks containing zircon, indirect evidence or computer modelling.
In his new work of Geophysics decided to explore what could happen to the Earth after a collision with a large enough meteorite. About 4 billion years ago collision with meteorites was one of the main factors determining what is happening on the Ground. Scientists have suggested that a large meteorite could have caused the formation of the modern lithosphere and its tectonic movements.
To test their hypothesis, the researchers conducted a computer simulation of events that could occur with the mantle and the lithosphere after the fall of the meteorite, using the method of Monte Carlo. In the model, they used data on the number and size of the asteroids at this stage of the development of the Solar system, their likely speed and heat flow in the clash.
Computer simulations showed that the fall of the meteorite leads to the excitation temperature anomalies in the mantle. This anomaly develops and causes the rise of water from deeper layers to the outside and dive initially formed layers of the earth’s crust into the mantle.
Modeling the processes taking place from outer layers of the crust of kataria after a collision with meteorites of different sizes, the researchers showed that in response to any strong initial perturbation at the moment of collision in the earth’s mantle begins a slow transition to steady state with a fairly thin crust and subduction zones. However, this condition differs from the modern, so scientists have suggested that the formation of the modern earth’s crust has occurred successive collisions with a few meteors (radius of one of them were to be not less than 1 thousand km).
As a result of these clashes could be formed in the oscillating mode with two metastable States. The simulation results showed that between these States there have been several transitions with a period of about 100 million years, then about 4 billion years ago by the cooling and thickening of lithosphere (and perhaps even multiple collisions with smaller meteorites) formed a relatively stable brand new condition, similar to today.
The study also showed that, in addition to tectonic movements, such a collision could lead to the formation of the modern Earth’s magnetic field, which is formed by the mechanism of magnetic Dynamo and is quite sensitive to heterogeneities in the mantle.
It is worth noting that the obtained results was confirmed by data from recent geological investigations. If initially it was thought that tectonic movements began around 3 billion years, the analysis of isotopic composition of Titan showed that it happened not later than 3.5 billion years ago.