The process is called “lithospheric dripping” and , apparently, has been occurring for millions of years and in many places on our planet; among them, the central Anatolian Plateau of Turkey and the Great Basin of the western United States. However, until a few years ago we had no record of this.
Now, a new geological experiment has resulted in the discovery that the earth’s crust has been “dragged” for hundreds of kilometers also in the Andes Mountains after being swallowed by the viscous mantle. Thus, below this well-known terrestrial mountain range, parts of the outer crust of the Earth have sunk into a layer of the mantle, slowly dripping into the interior of the planet as if it were honey.
What happens on the surface when the crust starts to leak?
This has been going on for millions of years: a long geological process that has produced telltale wrinkles and other features on the surface that scientists have discerned through modeling and experimentation. As the rocky crust heats up to a certain temperature, it begins to thicken and drip down into the mantle. This formation and release of droplets from the crust has effects on the surrounding surface of the planet.
“We have confirmed that a deformation in the surface of an area of the Andes Mountains has a large part of the lithosphere below the avalanche,” said geology graduate student and lead author of the study Julia Andersen of the University of Toronto in Canada. “Because of its high density, it dripped like cold syrup or honey deeper into the planet’s interior and is probably responsible for two major tectonic events in the central Andes: changing the surface topography of the region by hundreds of kilometers and crushing and stretch the superficial crust itself”.
“Overall, the results help define a new class of tectonic plates and may have implications for other terrestrial planets that do not have Earth-like tectonic plates, such as Mars and Venus,” says the researcher.
The geology of the Earth
We can divide it into two parts: a crust and an upper mantle that form rigid plates of solid rock, the lithosphere; and the hotter, more pressurized plastic rocks of the lower mantle. Lithospheric (or tectonic) plates float in this lower mantle, and their magmatic convection currents can pull the plates apart to form oceans; rubbing against each other can cause earthquakes; and they can also collide, slide under one another, or expose a gap in the plate to the fierce heat of the mantle to form mountains. But according to these results, it seems that they are not the only processes by which mountains can be formed. Also with the lithospheric drip. As the droplet filters down into the mantle, its weight pulls on the upper crust, forming a basin on the surface. Eventually the droplet’s weight becomes too great for it to remain intact; it breaks apart, and the crust above it springs upwards for hundreds of kilometers, forming mountains.
“We compared our model results with geophysical and geological studies conducted in the central Andes, particularly in the Arizaro Basin , and found that changes in crustal elevation caused by lithospheric dripping in our models follow very well the changes in the elevation of the Arizaro basin,” says Andersen. “We also observed pleated crustal shortening in the model , as well as basin-like depressions on the surface, so we are confident that dripping is very likely to be the cause of the observed deformations in the Andes.”
According to experts, there may be other regions of the world where different types of lithospheric dripping can be observed.
Referencia: Andersen, J., Göğüş, O.H., Pysklywec, R.N. et al. Symptomatic lithospheric drips triggering fast topographic rise and crustal deformation in the Central Andes. Commun Earth Environ 3, 150 (2022). https://doi.org/10.1038/s43247-022-00470-1
