Most geologists believe the Himalayas\u2019 immense height results from thickening of the Earth\u2019s crust.<\/p>\n
However, a new study suggests the geology beneath the world\u2019s tallest mountain range is much more complex, proposing a novel crust-mantle-crust structure.<\/p>\n
To unravel the deep dynamics, researchers from the University of Milano-Bicocca in Italy ran complex 2D numerical simulations, playing with different crust and mantle properties.<\/p>\n
Decoding the Himalayan formation<\/p>\n
The Himalayan mountains<\/a> formed in the collision between the Asian and Indian continents around 50 million years ago.\u00a0<\/p>\n The prevailing scientific explanation for the Himalayan-Tibetan orogen was a Swiss geologist \u00c9mile Argand\u2019s theory<\/a>, which was revealed in 1924.<\/p>\n The theory suggests the continuous collision of the Indian and Asian plates caused their crusts to thicken, reaching depths of 70\u201380 kilometers. <\/p>\n This immense, single layer of crust could have provided the support for the massive mountain peaks and the Tibetan Plateau.<\/p>\n But as scientific tools advanced, some cracks appeared in this long-held theory. One major concern? A crust thicker than 40 kilometers shouldn\u2019t be strong enough to support a massive plateau like Tibet.\u00a0<\/p>\n \u201cCrustal thickness above \u223c40 km implies reduced strength of the continental lithosphere, which may become unable to sustain a plateau the size of Tibet throughout much of the Cenozoic,\u201d the study noted.\u00a0<\/p>\n Furthermore, mounting geochemical and seismic evidence has shown the presence of mantle rock at depths where it shouldn\u2019t exist, which also conflicted with Argand\u2019s model.<\/p>\n A new study set out to reconcile these inconsistencies and understand the movement of the Indian and Asian plates.<\/p>\n Researchers performed over 100 numerical simulations<\/a> of the continental collision, comparing their models to real-world seismic and geochemical data.<\/p>\n They changed the properties of the crust and mantle in the simulations to see how those changes affected the results. It offered a compelling alternative.<\/p>\n Instead of creating a single, overly thick crust, the simulations showed that the collision of the plates most likely formed a crust-mantle-crust sandwich.\u00a0<\/p>\n This structure, which the study also calls crustal doubling, consists of a layer of Indian crust, a central layer of rigid Asian mantle, and an upper layer of Asian crust.\u00a0<\/p>\n The arrangement suggests that the region\u2019s colossal elevation is supported not by one massive crustal slab, but by a complex, layered architecture.<\/p>\n Layered structure <\/p>\n During the simulations, researchers observed that the Indian crust<\/a> didn\u2019t just slide beneath the Asian crust; it moved under the entire Asian lithosphere, a rigid layer including the crust and the upper mantle. <\/p>\n As it descended, the Indian crust was subjected to immense heat, causing it to liquefy. Portions of this now-molten crust rose and were underplated, or pushed up, into the area beneath the Asian mantle section. <\/p>\n This process essentially created a deep, layered geological structure.<\/p>\n \u201cWe propose that viscous underplating of Indian crust beneath Asian lithosphere, not crust, forms the overall architecture of the Himalayan-Tibetan orogen,\u201d the study stated.<\/p>\n The new explanation better fits prior observations, such as the evidence of mantle rock closer to the surface than expected.<\/p>\n The researchers believe their findings offer a more comprehensive understanding of how mountains<\/a> are built and could be applied to other regions.\u00a0<\/p>\n