The forces that make the world’s highest mountains rise to the skies operate deep beneath the Earth’s skin. Geologists have some idea of the mechanism, but the evidence so far leaves plenty of room for debate over the details.
A new look at previous research and recent analysis of new seismic data collected from across southern Tibet provides a surprising picture of the enormous forces at work beneath the Himalayas.
Announced at American Geophysical Union Conference In San Francisco last December, researchers from US and Chinese institutions reported how the Indian continental plate is collapsing as it grinds beneath the overlying Eurasian tectonic plate.
This is a surprising compromise to the two models currently favored to explain the uplift of the Tibetan Plateau and the mighty Himalayas.
Both cases are caused by collisions between masses of Earth’s crust belonging to India and Eurasia. Beginning about 60 million years ago, the Indian plate was pushed under its northern neighbor by flows of molten rock in the mantle.
Little by little, Eurasia is being lifted skyward on the shoulders of a drowned giant, giving it the highest altitude of the Earth.
Studies of the density of the mantle and crust suggest that the highly buoyant Indian continental plate cannot sink so easily, but this is because the sunken parts of the crust sink beneath the belly of the Eurasian plate. This means that there is a high possibility that it is still worn out. It plunged deep into the mantle.
Another possibility is that the Indian plate is warped, with some parts wrinkled or folded and others sinking or submerging.
Different perspectives emerge depending on what type of evidence is preferred and how the data is processed.
In a study led by Lin Liu, a geophysicist at Ocean University of China, researchers collected data from “above and below”. S wave and Shear wave division data Data from 94 broadband seismic stations placed from west to east across southern Tibet was combined with previously collected “round trip” data. P wave data To come up with a more nuanced view of the dynamics below.
The researchers determined that the Indian plate was not simply moving smoothly beneath the Eurasian plate, nor was it clustered together like a rug on a slippery floor.
Instead, its thick base has flaked off and its lighter upper half has sunk into the mantle as it continues its journey just below the surface.
Computer models had suggested that thick sections of some plates could break apart in this way, but this study provides the first empirical evidence that it is happening.
The researchers’ explanation is consistent with geological models based on the limits of helium-3-rich springs and patterns of near-surface cracking and earthquakes, which together suggest parts of the ancient Indian plate are largely intact. Looks like it corroborates the massacre map below. etc. break apart about 100 kilometers underground, allowing the base to warp into the planet’s molten core.
A clear 3D representation of the boundaries and boundaries where plates slide against each other would not only help us understand how our surfaces came to look the way they do, but also inform how we predict earthquakes in the future. may be able to provide information.
This research was presented at the 2023 International Conference. American Geophysical Union Conference. A pre-print copy of the study is available below. available online.