Hidden layers of molten rock lie beneath the earth’s crust!
Recently, researchers have discovered something new about a layer of partially molten rock that lies beneath the Earth’s cold outer crust.
This elastic band of hot matter is known as the asthenosphere, or loose shell, and is generally considered to be solid, with some liquid matter weakening the overall structure.
However, its top layer turned out to be much softer than scientists thought.
A study by scientists at the University of Texas has revealed the varying flow and density characteristics of the thin portion of the asthenosphere, resolving the boundaries of regions within the layer that can extend across the entire globe. A clear map of the variation in seismic wave echoes passing through the Earth’s interior can help us pinpoint the actions that drive the planet’s floating tectonic plates.
The discovery adds vital details to the global structure of the upper mantle, allowing geologists to rule out any influence this soft region of the upper mantle has on the overall ripples of the asthenosphere.
“We can’t rule out that local melting doesn’t matter,” admits physicist and geophysicist Thorsten Becker of the University of Texas. “But I think it encourages us to consider these melting observations as a sign of what’s going on in the ground.” , not necessarily as an active participant in anything.”
Although some previous research suggested that the asthenosphere was interrupted by occasional bursts of magmatic activity, it was not clear until recently how widespread this phenomenon was.
For the new study, Baker and colleagues created a global map of the globe using mantle seismic images collected from stations around the world.
When the seismic waves sent by these stations above the Earth hit the upper part of the asthenosphere, they slowed down significantly, which indicates that the upper layer is more molten than the rest.
More liquid materials usually provide more flow, but this is not necessarily the case here.
Scientists’ map of the asthenosphere does not match the movement of tectonic plates above. For example, regions where seismic waves move more slowly do not show more tectonic activity.
“When we think about melting, we intuitively think that melting should play a large role in the viscosity of the material,” says Junlin Hua, research leader, “but we found that even when the proportion of melting is very high, its effect on the flow of the mantle is small.” Extremely”.
Oddly enough, there seem to be several pockets of magma scattered throughout the asthenosphere, and not just at the top, where hot magma usually accumulates at depths of 100 to 150 kilometers (about 60 to 90 miles).
In the lower part of the asthenosphere, for example, magma usually arises, perhaps as a result of desiccating melting, which can occur when rocks are not saturated with water.
On the other hand, the middle layer with a depth of about 260 km is not widespread, but appears sporadically and may be the result of carbon melting of the mantle.
Scientists have long suspected that the Earth’s tectonic plates are driven by flows of molten rock deep below the surface, but the exact dynamics of the rise and fall of gas, liquid, or rock is unclear.
Based on current findings, the University of Texas researchers believe that gradual changes in temperature and pressure in the asthenosphere are causing a deep flow of molten rock. The overall viscosity of this region is not a big factor when it comes to the movement of overlying tectonic plates.
The study is published in the journal Nature Geoscience.
Source: Science Alert
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