The colossal collision of tectonic plates that created the Himalayas and Tibetan Plateau may be causing the Indian tectonic plate to split apart underneath southern Tibet, according to new research. This rare event could have major implications for earthquake hazards and landscape evolution in the region.
Signs the Indian Plate Is Breaking Up
Analyzing over 20 years of earthquake data in southern Tibet, geophysicists have detected a slowly emerging split in the Indian tectonic plate beneath the surface. This break runs for nearly 1000 km in an east-west orientation underneath the high mountains of the Himalayas and Tibetan Plateau.
The presence of two sub-parallel zones of earthquakes at different depths indicates that the lower Indian Plate is detaching itself from the upper part along this fracture. The upper layer seems to be stuck to Asia as it continues to push northwards, while the lower layer is splitting off and sliding under the Tibetan Plateau.
This break-up of the Indian Plate is likely being driven by the ongoing collision between India and Eurasia, which began over 50 million years ago. The intense compression forces generated by two continents crashing into each other has led to immense crustal shortening and thickening, uplifting the Himalayas and Tibetan Plateau to their current high elevations.
Table 1: Key Evidence Supporting Indian Plate Split
| Type of Evidence | Details |
|---|---|
| Seismic activity | Two parallel belts of earthquakes at different depths suggestive of a detachment zone |
| GPS surface movements | shear motion consistent with subterranean plate rupture |
| Gravity anomalies | Light upper crust over dense lower crust |
| Magnetotelluric data | Low electrical conductivity indicative of fluids along rupture |
This collision zone is the site of the largest and fastest continent-continent collision happening today on Earth. The continual northerly push of the Indian Plate generates immense tectonic stress in the crust and upper mantle beneath southern Tibet. The Indian lower crust and lithospheric mantle are becoming so severely shortened that they are now splitting off from the rest of the plate.
Monitoring a Rare Event
The break-up of a tectonic plate at a collision boundary is an exceptionally rare event in Earth’s history – which is why this emerging split of the Indian Plate has generated so much buzz among geologists. The only other clear example of plate rupture is from the Afar Triangle region in East Africa, where the continental lithosphere has ruptured and a new ocean basin is forming as the African and Arabian Plates diverge from each other.
However, the split occurring deep under the Tibetan Plateau is driven by convergence rather than divergence. The mechanisms facilitating the detachment of Indian lower lithosphere here are not fully clear, but likely involve a combination of ductile shearing, eclogitization reactions, and fluids weakening the rocks. Unraveling the processes at work will shed new light on the behavior of plates during continental collisions.
The discovery of this plate rupture was enabled by substantial improvements in seismic monitoring and geophysical imaging beneath Tibet over the past few decades. Dense arrays of seismometers across Tibet and the Himalayas have provided unprecedented coverage of earthquake activity at different depths and locations. Meanwhile, gravity studies, magnetotelluric surveys, and other measurements have built up a detailed picture of the subsurface structure and properties.
By integrating these multiple lines of geophysical evidence, the imprint of the slowly developing Indian Plate breakup has now become evident. But many questions still remain regarding how fast this split is progressing, how extensive it is, and what will be the direct impacts on regional geology and earthquake hazards.
Table 2: Timeline of Collision Between India & Eurasia
| Time Period | Tectonic Event |
|---|---|
| >100 million years ago | India separated from Madagascar as part of Gondwanaland breakup |
| ~55 million years ago | Collision between Indian Plate and Eurasia begins |
| Last 20 million years | Acceleration of Indian Plate, major crustal shortening |
| Past 10 million years | Uplift of Tibetan Plateau to current elevations |
| Present day | Indian lower crust and mantle detaching beneath Tibet |
Ongoing real-time seismic monitoring and repeated geodetic and geophysical surveys across Tibet and the Himalayas will thus be crucial to track how the split is evolving. Sophisticated numerical modelling studies should also provide vital additional insights into the mechanics and dynamics of this plate rupture process.
“We will need to watch this place very carefully over the coming years,” says Dr. Yongjie Xie, lead researcher from the University of Science and Technology of China. “Using the latest data analysis techniques, we may be catching this plate split at a relatively early stage so we can properly investigate the processes in action.”
Impacts and Future Evolution
The effects of the Indian Plate splitting apart beneath southern Tibet could potentially be very significant for both regional geology and understanding earthquake triggers. But given the early phase of the rupture, uncertainties still remain regarding how it might directly impact the landscape or seismic hazard.
In terms of landscape impacts, some researchers suggest that once the lower part of the plate fully detaches, it may remove support underneath Tibet. This could enable renewed uplift and expansion of the plateau as hotter, lower-density mantle rocks flow in underneath to take the place of the subducted Indian lower lithosphere. Any resurgence of the plateau surface could reactivate uplift in adjacent regions like the Himalayas, influencing river profiles and erosion patterns.
However, others experts argue that loss of the lower lithosphere may not necessarily cause an increase in Tibetan surface elevations, especially considering the plateau interior is already underpinned by hot mantle material. Much more work is required to determine the consequences of the plate split on regional geology and geomorphology.
In terms of earthquake risks, the zone of plate rupture itself could generate sizable earthquakes as the lower crust and upper mantle shear off. Stress redistribution as support underlying parts of Tibet gets removed could also potentially trigger quakes in some areas. However, a more prevalent view is that releasing tectonic strain along this sub-horizontal shear plane might relieve stress accumulation elsewhere and even dampen earthquake incidence regionally.
Clearly long-term, fine-scale seismological monitoring across southern Tibet and the adjoining Himalayas will be crucial for detecting any evolving earthquake patterns linked to the plate split. Advanced warning of hazardous quakes may be possible if reliable seismic precursors can be identified around the fracture.
Outlook Moving Forward
The revelation that the Indian Plate is bifurcating beneath Tibet poses more questions than it answers for now. But the discovery provides an unprecedented window into the extreme tectonic forces unleashed during continental collisions and subduction initiation. It also opens up new avenues for studying how plate dynamics stimulate earthquake triggering, mountain building, and the evolution of continental lithosphere.
“These types of rare experiments in nature generate important data that helps refine and validate the physics in our numerical models,” explains Dr. Xie. “We will keep deploying the latest instruments and analysis techniques to follow the crack propagation and deformation in close detail in the coming years.”
Constraining the fate of the bifurcating Indian Plate and its implications for regional geology will also require pulling in expertise across the geosciences. Combining insights from seismologists, structural geologists, geochemists, geodynamic modelers, and other researchers will be key to fully unravel the mechanisms and impacts of this momentous plate split transpiring beneath the world’s highest plateau.
What is clear for now is southern Tibet demands even closer inspection to monitor how the subterranean crack continues creeping eastwards – potentially heralding the lower Indian crust’s eventual dematerialization. The high Himalayas may still have some unexpected tricks up their sleeves when it comes to stupendous tectonic spectacle.
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