Amber Madden-Nadeau is studying Geology at Imperial College London. Amber recently wrote a report on the geology of the Himalayas, with a focus on the Ladakh region, as part of our hazards education project. Here, Amber summarises the important aspects of Himalayan geology and the influence they have on people’s lives.
The Himalaya mountain range stretches over 2500km, influencing the lives of people who live across this wide area. The formation of the Himalayas occurred in two stages. India collided with Eurasia at some point between 65 million years ago (Ma) and 45Ma, creating the Indus Suture. During the second stage, in which the uplift of the Himalayan Mountain Range began to occur, the India plate was thrust further beneath the Eurasian plate. The pressure and temperature increase caused the rocks to recrystallize, forming minerals which reduced friction and enabled further thrusting. This occurred at about 20Ma, however the Himalayas did not reach their present height until between 2.5Ma and 1.8Ma.
The uplift of the Himalayas had an effect on climate circulation, and the region began to experience monsoons. The heating of the Tibetan plateau provides the required thermal gradient to drive the South Asian summer monsoons. In addition to this, as a result of the uplift, the region began to experience high altitude glaciation. In Ladakh, the monsoonal moisture supply has been blocked by the uplift of Himalayan ranges, such as the Karakorum, resulting in glacial retreat. More recently, climate change has accelerated the shrinking of Himalayan glaciers.
The majority of the convergence of India and Eurasia occurs due to slip on faults in temporally localised events, which generates earthquakes. These can be of relatively high magnitude, as shown by the Wenchuan Earthquake in the Longman Shan region, which was of magnitude 7.9. Earthquakes present a major geo-hazard in the Himalayas, but with a relatively long repeat time.
The Ladakh region is experiencing movement at a slow pace of approximately 3.4mm/year along the Karakoram fault. Ladakh has impressive hydrothermal reserves, which are currently unharnessed. These occur due to the accumulation of magma close to the surface, which heats up the groundwater, causing it to circulate. There are 20 hot springs within the area with three sites which theoretically could produce >20MWe of energy. The most important of these is the Puga valley, where up to 5000MWh could be harnessed. Power cuts are not uncommon Ladakh and the surrounding area, particularly during winter. The Indus River freezes during this time, which causes their hydropower plants to fail. Metal deposits can also be associated with hydrothermal systems and the area has an abundance of rubies due to the intense metamorphism that has occurred there.
Despite these possible economic benefits, the mountains surrounding Ladakh create a landslides risk. This is due to the steep slopes: two thirds of all rock avalanches occur on the steepest 5% of the Earth’s surface. The steeply dipping beds are created by the deformation that has occurred in the area, which creates arch-like folds. Other factors that aid the formation of landslides include glaciers and rivers undercutting rock, heavy rainfall, melting glaciers, layering within rock and weaknesses such as fractures and movement on faults. 14 out of 16 large landslide deposits recorded and dated within the area occurred during monsoons, suggesting that rainfall is a common trigger mechanism. The region experiences earthquakes and these could also be a significant trigger.
The Himalayas are very dynamic, generating hazards such as earthquakes and landslides, but also economic opportunities such as hydrothermal energy and tourism. Glaciers provide the local people with a water store, but this needs to be carefully managed due to the accelerating retreat of the ice. It is important to understand the geology of the Himalayas in order to be able to work towards a sustainable future, mitigating the risks that hazards pose but also managing and harnessing the available resources.
A fully referenced version of Amber’s report can be found here.
Ryan
Hi Amber,
I am quite interested in the geology of the Manali region, including the metamorphic boulders, their ages and sequences of activity. I’ve found it very difficult to find info on Indian geology and was wondering if you could contact me with any info or references.
Great write up! The Solong pass was closed the last 2 times I was there, so I never made it further north.
Thanks