Scientists have discovered that the Earth’s crust is dripping “like honey” into our hot interior of the Andes Mountains.
By setting up a simple experiment in a sandbox and comparing the results with actual geological data, the researchers found compelling evidence that Earth The avalanche took place hundreds of miles across the Andes after being swallowed up by the sticky mantle.
This process, called rock drip, has been occurring for millions of years and in multiple locations around the world — including the Central Anatolian Plateau in Turkey and the Great Basin of the western United States — but scientists only learned about it in recent years. The researchers published their findings on the Andean distillation on June 28 in the journal Nature: Earth and Environment Communications (Opens in a new tab).
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“We have confirmed that there is deformation on the surface of an area of the Andes with a large part of the lithosphere [Earth’s crust and upper mantle] Below is mired in meltdown,” Julia Andersen, a researcher and doctoral candidate in Earth sciences at the University of Toronto, He said in a statement. “Because of its high density, it has been dripping like cold syrup or honey deeper into the planet’s interior and is likely responsible for two major tectonic events in the central Andes – shifting the region’s topography by hundreds of kilometers and crushing and extending the surface crust itself.”
The outer regions of Earth’s geology can be divided into two parts: a crust and an upper mantle that form solid plates of solid rock, the lithosphere. and the hotter, more compact the plastic-like rocks in the lower mantle. Lithosphere (or tectonic) plates float on this lower mantle, and magmatic convection currents can separate plates from each other to form oceans; rubbing them against each other to cause earthquakes; It collides with them, slides one under the other, or a gap in the plate exposes the mantle’s intense heat to form mountains. But, as scientists are beginning to observe, these aren’t the only ways mountains can form.
Lithosphere dripping occurs when two plates of the lithosphere collide and crumble upwards so much that they condense, resulting in a long, heavy droplet that seeps into the bottom of the planet’s mantle. As the drop continues to seep down, its increasing weight pulls on the crust above, forming a trough on the surface. Eventually, the weight of the drop becomes too great to remain intact; The long lifeline ruptures, and the crust above it springs upward through hundreds of miles – forming mountains. In fact, researchers have long suspected that such subsurface expansion may have contributed to the formation of the Andes.
The Central Andean Plateau consists of the Puna and Altiplano plateaus – an area stretching 1,120 miles (1,800 km) and 250 miles (400 km) wide, stretching from northern Peru through Bolivia, southwest Chile, and northwest Argentina. It was created by the subduction, or sliding beneath, of the heavier Nazca Tectonic Plate under the South American Tectonic Plate. This process deformed the crust above, and pushed it thousands of miles into the air to form mountains.
But subduction is only half the story. Previous studies It also refers to features in the central Andean plateau that cannot be explained by the slow and steady upward thrust of the subduction process. Instead, parts of the Andes appear to have arisen from sudden upward pulsations in the crust throughout the Cenozoic Era — Earth’s current geologic period, which began about 66 million years ago. The Bona Plateau is also higher than the Altiplano and contains volcanic centers and large basins such as the Arizaru and Atacama.
These are all signs of dripping lithosphere. But scientists certainly need to test this hypothesis by modeling the floor of the plateau. They filled a glass tank with a material that mimics the Earth’s crust and cover, using polydimethylsiloxane (PDMS), a silicone polymer about 1,000 times thicker than table syrup, for the bottom lid; mixture of PDMS and upper mantle modeling clay; and a sand-like layer of fine ceramic balls and silica balls for the veneer.
“It was like creating and destroying tectonic mountain belts in a sandbox, perched on a simulated basin of magma — all under very precise conditions of only millimeters,” Andersen said.
To simulate how droplets form in Earth’s lithosphere, the team created small, high-density instabilities above the lower mantle layer of their model, recording with three high-resolution cameras as the droplet slowly formed and then descended into a long, puffy droplet. “Drip happens over hours, so you won’t see a lot happening from minute to minute,” Andersen said. “But if you check every few hours, you will clearly see the change – it just takes patience.”
By comparing their model surface images with aerial photographs of geological features of the Andes, the researchers saw remarkable similarities between the two, strongly suggesting that the features in the Andes were indeed formed by rocky drip.
“We also observed crustal shortening with folds in the model as well as trough-like depressions at the surface, so we are confident that dripping is the cause of the observed deformations in the Andes,” Andersen said.
The researchers said their new method not only provides strong evidence for how some key features of the Andes were formed, but also highlights the important role of geological processes beyond subduction in shaping Earth’s landscapes. It may also prove effective in detecting the effects of other types of underground droplets elsewhere in the world.
Originally published on Live Science.
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