North America flows from below, discover the geoscientists

The researchers discovered that the underside of the North American continent flows into rock spots – and that the remains of a tectonic plate flowing in the mantle of the earth can be the reason.

An article published in Nature geoscience Describes the phenomenon, discovered at the University of Texas in Austin. This is the first time that “Cratonic slimming” can be captured in action.

“We have made the observation that there could be something under the Craton,” said the main author of the Junlin Hua study, who conducted research during a postdoctoral scholarship at the Jackson School of Geosciences of the UT. “Fortunately, we also had the new idea of ​​what motivates this clarification.”

Cartons are very old rocks that are among the continents of the earth. They are known for their stability and their ability to persist for billions of years. But sometimes, cratons undergo changes that can affect their stability or eliminate whole layers of rock.

For example, the Craton of Northern China lost its deepest root layer millions of years ago.

What makes the discovery of Special Dripping Cratonic, said that researchers is that it happens right now. This allows scientists to observe the cratonic thinning process as and when.

The runoff is focused on the Midwest of the United States. It is not necessary to worry about the continent by avoiding or the drip that changes the landscape of any time, assure the researchers. The processes of the mantle that drive the drops can influence how tectonic plates evolve over time, but they in progress very slowly. In addition, dripping should finally stop while the remains of the tectonic plate sink more deeply into the coat and its influence on the Craton fades.

The discovery is the most important for the geoscientists who study the continents for their entire lifespan, said co-author Thorsten Becker, professor in the Department of Terre de la Jackson and the Planetary Sciences and the Geophysical Institute.

“This kind of thing is important if we want to understand how a planet has evolved over a long time,” said Becker. “It helps us understand how to make continents, how to break them and how to recycle them (in the ground.)”

The dripping discovery has come out of a wider project led by Hua, who is now a professor at the University of Science and Technology in China, which has created a new seismic tomographic model full of waves for North America using an approach developed by the co-author Stephen Grand, who is now a professor emeritus at the Jackson School and his team. This computer model, which uses seismic data collected by the Earthscope project, has revealed new details on the geological processes that occur in the crust and the underlying coat to North America.

“Due to the use of this complete waveform method, we have a better representation of this important area between the deep mantle and the less deep lithosphere where we would expect clues to what is happening with the lithosphere,” said Becker.

This model put the drops in sight for the first time in this way. This has also helped researchers to deduce that the Farallon plate, an ocean tectonic plate that has been subduing under North America for about 200 million years, could lead the process despite its separation from the Craton of approximately 600 kilometers.

The plate, which was initially seismic imagined in the 1990s by Grand, played an important role in the formation of the North American plate. The researchers think that it is now worn on the continent from below by redirecting the flow of material of the mantle so that it shears the bottom of the craton and by releasing volatile compounds which weaken its base.

Although dripping is concentrated in an area of ​​the Craton, Hua said that the plate seems to interact with materials from all over the Craton, which covers most of the United States and Canada.

“A very wide range is lightening,” said Hua.

When the researchers built a computer model of these dynamics, the Craton model sank when the Farallon plate was present. When the plate was removed, the drip stopped.

Becker recognizes that IT models have limits. But the resemblance of the model with the data is a good sign, he said.

“You look at a model and say:” Is it real, are we too interpreted from the data or does he say something new on earth? “” Said Becker. “But it looks like many places that these blobs come and go, that it is (showing us) a real thing.”