How deep is the continental plate? 80-120 miles below sea level

A recent study shows that scientists use seismological data for each continent in the world and find that the continental plate begins to extend downward at 80-120 miles below the surface, and the continental plate boundary is about 100 miles below the surface. According to foreign media reports, scientists believe that they have answered a question: how deep is the Earth’s mainland plate? At present, Brian Savage, a seismologist at the University of Rhode Island, points out that plate tectonics is a relatively new theory that exists only for about 50 or 60 years and I always tell my students Compared with the theory of Earth evolution, the latter theory has been proposed for 150 years, and current and magnetic theory of the proposed time is similar. In half a century, the theory of the Earth plate is universally accepted by geologists, and the plate tectonics is the theory that the continental plate drifts and the ocean crosses on the surface of the earth for hundreds of millions of years. Based on the theory, American researchers know why the earthquake occurred, and why Africa and South America can be put together. At the same time, geologists have mastered a number of people do not realize some of the knowledge, such as: the ocean plate density is greater than the continental plate, the ocean plate is always under the mainland. But the plate tectonics still can not answer some pressing questions about the earth system, they are not sure how the mainland is formed, at the same time, they are not sure whether the mainland deformation or destruction. Until recently, they can not confidently answer this question: how deep is the mainland plate?


magazine last week’s “Science” published a new study reports may end this debate, the use of global seismological data for each continent, the paper found that the continental plates begin at 80-120 miles below sea level Extends downwards.

In other words, the distance between people now and the edge of space is less than the distance from the bottom of the continental plate. This latest study will help scientists enhance our understanding of the plate mechanism, not only the depth or composition of the continental plate, but also more about how the Earth plate moves. The earth is divided into many different layers, the primary education is very familiar with the crust, the crust is located 30-40 miles below the surface, the silicate mantle is located 1800 miles below the surface, the internal and external cores are below the surface 3959 miles Where the Earth’s core is a hot iron and nickel.

But these familiar terms describe only the different layers of the Earth’s structure and its chemical composition, and do not describe how the plates move and react with heat. Thus, geologists use more special words to describe the stratigraphic structure of the earth – lithosphere and asthenosphere.

is not involved in the study at Rice University geologist Cin-Ty Lee said: “Imagine you pop a freshly baked hot fudge chocolate cake from the oven, at the beginning of cake all the liquid, After which it will start to cool from the top and then produce a hard shell. The top of the cake is like the earth’s lithosphere, which is the uppermost part of the earth. “

The lithosphere can also be understood as the tectonic plate A layer, the lithosphere below the warm part of the composition of the soft stream layer. For the observer, the asthenosphere will be like a rock, but for millions of years, its role is like a slow and bulky fluid on the trenches, and mixed with them.

In fact, lithosphere and asthenosphere have similar chemical properties, especially where the boundary is particularly pronounced. But the heat difference between the two is very obvious, the Earth’s internal temperature is about 1400 degrees Celsius, while the surface temperature is only 25 degrees Celsius.

Cin-Ty Lee said: “From 1400 degrees Celsius to 25 degrees Celsius, which is the lithosphere.” A long time ago geologists have identified the geochemical layer, scientists can be through the earthquake station or gravity sensor satellite Direct observation and study of the Earth’s surface, but these techniques are difficult to determine the boundaries of the lithosphere. More importantly, scientists often come to the conflicting results: some people assess the depth of the lithosphere based on the diamond near the volcano; others try to determine the depth of the lithosphere by measuring the seismic waves through the interior of the earth. According to the Diamond Information Assessment, the lithosphere is closer to the Earth’s surface, about 100 miles underground. Saikiran Tharimena, a researcher at the University of Southampton, said the latest study had more information and more resolution, analyzing the information of each continent to assess the depth of the lithosphere. We studied the seismic wave data generated by the world’s magnitude 5.5 above 1990-2015, and the team also analyzed the central part of the plate – the central position of the Canadian shield, not by the rocky and discontinuous coasts.

Based on more database information support, modeling is even simpler, and researchers can see that there is a huge line of “diamond information lines” 80-130 miles below the surface. This discovery will be of great significance to our understanding of the continental plate. The traditional view is that the continental plate system is floating on the underground magma on the huge land. However, the truth is more or less dramatic, Saikiran Tharimena and colleagues say that the rocks in the mantle are slightly melted by increasing pressure on the lower boundary of the lithosphere, and in general the rock at the top of the asthenosphere may melt by 1% Kind of seemingly insignificant melting is enough to lubricate the continental plate to produce drift.

We look at the results tableThe lower boundary of the paleosphere is obvious, for example, the oscillatory velocity of the lower boundary of the asthenosphere will change abruptly, and because of its rapid change, it is unlikely that due to changes in heat or chemical properties. “The only way to change the speed is hard to achieve,” says Cin-Ty Lee. “The only way is to increase the liquid phase.”

The study did not answer whether the presence of liquid melt was causally Relationship, or whether this is only a by-product of history. In other words, the continental plate is now about 100 miles below the surface, but this distance may be a chemical chance, not a permanent feature of the earth. It now appears that the thickness of the lithosphere conforms to this description, but that does not mean that the earth’s history or the future is like that.

Saikiran Tharimena said the next step will be to use high-resolution techniques to analyze a wider range of lithosphere, especially in the ocean-land intersecting region. This will help us understand where the lithosphere ends, and where the more intense asthenosphere begins, which will help answer a bigger question: how is the Earth continent formed? (Allure)

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