It鈥檚 home to the highest points on planet earth, but until recently, there were aspects of the Himalayan mountain ranges that geologists simply could not explain.
In particular, scientists were uncertain just how, exactly, the mountains formed. The most common argument was that they were entirely the result of India鈥檚 land mass moving into Asia. But new Dal research suggests a different answer, buried deep within a complex fault system in western Nepal.
鈥淚t鈥檚 going to change the way geologists are thinking about this,鈥� says Earth Sciences鈥� John Gosse. 鈥淕eodynamicists studying the world鈥檚 biggest and most iconic mountain range will probably need to incorporate this going forward.鈥�
Dr. Gosse teamed up with fellow Dal researchers David Whipp and Chris Beaumont (both in Oceanography) on 鈥淟imit of Strain Partitioning in the Himalayas Marked By Large Earthquakes in Western Nepal,鈥� published in the recent edition of Nature Geoscience (the other coauthors were Michael Murphy, Michael Taylor and C.R.P. Silver). It is the first study of is kind to investigate this particular fault system. 聽
The compression of the Indian plate and Asian plate as they press together was believed to be responsible for the high peaks throughout the entire range, from China to Pakistan. However, this new fault line shows that the two plates are also moving sideways, pulling apart in the area of the new fault.
鈥淏ecause the plate boundary is curved, we鈥檙e getting a side-by-side motion away from the centre of the range front,鈥� says Dr. Gosse. 鈥淣ow we have to modify the way we believe the Himalayas are actually forming.鈥�
From Google Earth to mountain hikes
Interestingly, the fault was first discovered digitally: Michael Taylor of the University of Kansas noticed the fault when virtually touring the area on Google Earth and quickly called on expertise of Dr. Gosse and the other researchers.
鈥淏efore we had Google Earth, we would have needed to get photos from the Nepal government, for example, and it could鈥檝e taken a long time and lots of money,鈥� says Dr. Gosse. 鈥淭his beautiful, big fault was immediately apparent, just absolutely gorgeous from a geologist perspective. Rather than wait for a proposal, we figured, 鈥楲et鈥檚 just get going on this.鈥� We scraped some money up and got an expedition team together as fast as we could.鈥�
Flying into northwestern Nepal and hiking more than 40 km of the fault system by foot, much above 5000 m elevation, the field team worked to map, measure and collect radiocarbon samples to date the fault.
鈥淎s soon as we got to the High Himalayas, you really realize the scale of the mountains,鈥� says Dr. Gosse. 鈥淭he expedition took us 40 km along a river side path that paralleled the fault, then high up over some of the Earth鈥檚 highest topography. We passed above remote temples and pristine caves and gorges that were rarely visited by foreigners.鈥�
Modeling a safer future
A numerical model created by Drs. Beaumont and Whipp at Dal shows that in fact, the fault is incredibly significant. 鈥淚t would be difficult to convince anyone of the significance by just doing field work to document a fault; there are lots of faults all over the world,鈥� explains Dr. Gosse, who teaches Dal鈥檚 course on natural disasters. 鈥淭he model can now explain features that could never be explained before now. We just had to ask the right question.鈥� 聽
The fault not only may be the source of the devastating earthquakes in the area 500 to 600 years ago, but suggests the potential risk of another one today.
Prior to the study, the area was not identified as at risk for large earthquakes greater than Magnitude-8. Equipped with this knowledge, Dr. Gosse and the other researchers hope to continue to study the fault system, to map the rest of the more than 200 km length, to understand future risks.
鈥淵ou鈥檇 like to think that you鈥檙e going to help someone who is in charge of coming up with building codes for a local city,鈥� says Gosse. 鈥淲e鈥檙e trying to explain how the earth works, but in a very useful way that could actually save lives in the future.鈥�
Sharing this fault system discovery with many in the scientific community for the first time, Gosse will give a presentation at the next Atlantic Geoscience Society meeting in Wolfville.
鈥淣ot many projects you do in your career are on the biggest or best example, but finding something really new about the Himalayas which have been studied for over a century and coming up with something new with significance 鈥� you often don鈥檛 get a chance like that.鈥�