The Earth’s crust has been gradually consumed by the mantle over millions of years.
A recent study published in Nature: Communications Earth & Environment has identified the cause of surface deformation in a region of the Andes mountain range.
“Due to its dense composition, the Earth’s crust drips like cold syrup or honey deeper into the planet, potentially causing two major tectonic events in the central Andes, altering the surface topography over hundreds of kilometers, both cracking and stretching the surface crust,” stated researcher Julia Andersen from the Department of Earth Sciences at the University of Toronto, Canada, one of the lead authors.
Layers of the Earth – (Photo: BBC Science Focus)
This phenomenon, known as “mantle drip,” may sound strange, but it has occurred over millions of years in various regions around the world. It has previously been observed in the Anatolian Plateau in central Turkey and the Western United States several years ago.
To investigate the mystery occurring beneath the Andes, scientists combined simple sandbox experiments with detailed seismic data recorded in the area.
According to Live Science, the outer regions of the Earth’s geology, including the crust and upper mantle, form rigid plates of the lithosphere; while the hotter, more plastic rock under higher pressure converges in the lower mantle. These lithospheric plates float above the lower mantle, being dragged by convection currents within it.
The dripping of the lithosphere occurs when two lithospheric plates collide, shattering the contact zone, which creates a “drip” that includes both the Earth’s crust and part of the upper mantle, sinking down into the layers below. The weight of this lithospheric drip also pulls material from above downwards, deforming the surface.
Conversely, when the lithospheric drip falls, the adjacent lithosphere, which has been pulled down by the weight of the drip, is also “released,” bouncing back up to form mountain ranges.
Scientists suspect that this process, with multiple small lithospheric drips occurring, has caused the mantle and crust to be uplifted repeatedly, contributing to the majestic Andes we see today.
Previous studies have also pointed out “inexplicable” features in the Central Andean Plateau, which are not due to the familiar subduction processes in plate tectonics but may arise from sudden uplift events. This could indeed be the impact of mantle drip.
