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Ladakh: a tale of colliding continents


Through June and July, the timelines on a campaign at work had been shifting. Late hours, last-minute changes, overhauls on campaign materials, internal conflicts — July was exhausting, and I had little time to plan my break ahead. I had considered a trip through Spiti valley, but for a solo traveller, it seemed too remote, too uncharted. On a whim, I booked tickets to Ladakh — and in hindsight, this was perfect, as the stories about the floods and landslides in Himachal Pradesh, were terrifying (I hope to have a more in-depth, researched piece on that, someday soon).

A herd of male urial - a species of wild sheep native to Central Asia, making their way to their rutting grounds set against a backdrop of faults near the Hemis Shukpachan village, in Ladakh.

This wasn't to be my first trip to Ladakh, I had travelled there twice before in November 2017 and 2018. Those winter trips, when tourism comes to a crawl and most of Ladakh's highlights are inaccessible, were underatken to search for the elusive snow leopard. The first year, we spotted blue sheep, urial, red fox, Ladakh pika, bearded vulture, golden eagle, and many other birds against spectacular backdrops of gneiss and granite, but no snow leopards. In 2018, over a 10-day trip, we tracked and prayed for the snow leopard, and this time, caught sight of 3: a mother, with her 5-month-old cubs. For 15 minutes after sunrise and over 45 minutes at sundown, we watched this young family make its way through the stark, sand-coloured rocks that girdle the high-altitude village of Ulley.

Video credits: Surya Ramachandran, Snow Leopard Lodge, Ulley.

The third trip promised to be different — I'd be travelling to Ladakh in summer, and the landscapes, both geographical and cultural, would be very different. I had a million places on my list, but 10 days isn't a lot of time. Here are some of the places I visited, personally, and in my imagination — fuelled by the book, Colliding Continents by Mike Searle, which I started on the flight to Leh.

This isn't the first time I'm writing about Ladakh. I'd covered it in Edition 5, where I mentioned glacial formations and geo-destinations:



Traversing the lunar landscape of Ladakh is like following a rather messy trail of clues hinting at the collision of continents, the stitching together of landmasses, and the crumbling, and crumpling of behemoth mountain ranges. The exposures of igneous, sedimentary and metamorphic rocks tell of cataclysmic tectonic activity, the movement of past glaciers, the presence of ancient lakes, and the millennia-long influence of climate.

Let's travel back in time...around 140 million years ago, the Indian plate split up from the Gondwana supercontinent and started migrating northwards. This slow, languid journey took millions of years, and it wasn't until ~55 million years ago, that the Indian plate made contact with the Asian plate. Imagine the southern margin of the Asian continental crust as lighter armour, and the edge of the Indian plate as denser armour forged from oceanic crust. As these two mighty plates collided, the heavier Indian plate was forced beneath the Asian plate, creating a subduction zone.

There's a missing piece to this jigsaw puzzle that doesn't get mentioned as often. There's a third landmass or microplate — the Kohistan island arc, sandwiched between the Indian and Asian plates. Around 110 million years ago, an oceanic island chain of mountains known as Kohistan or the Kohistan-Ladakh block, lay to the south of the Asian continent. As the Indian plate inched northwards, it dove beneath the Kohistan-Ladakh terrain. (Today, the Kohistan island arc can be studied along the Karakoram highway that connects Rawalpindi in Pakistan to the Chinese border.)

Much like the medical term for the stitches that hold two tissues together, sutures, defined by intense deformation, mark where the continents were stitched together. The Main Karakoram Thrust-Shyok Suture marks the zone of collision between the Indian and Asian terrains, whereas the Indus-Tsangpo Suture marks the merger of the Ladakh-Kohistan terrain, with the Indian and Asian plates.

The sheer scale of the Indus-Tsangpo Suture zone is breathtaking - between the sharp, jagged edges, a blue-green layer of serpentinite bears testimony to the continental collision.

As the Indian plate descended into the depths of the Earth and reached the mantle, water that had been trapped in sediments and oceanic crust was released. This water seeped into the overlying Asian plate and triggered the formation of magma. As the magma reached the surface of the Asian plate, it resulted in extensive volcanism that welded the margins of these colliding continents. The magma that did not escape, solidified just beneath the surface into giant granite formations known as batholiths.

In geological terms, the terrains formed along subduction zones, are known as magmatic or volcanic arcs - the town of Leh and the settlements across Ladakh are partly straddling a magmatic arc.

During this collision, the deformed, northern edge of the Indian plate gave rise to the Himalayan range, whereas the crumbled southern margin of the Asian plate created the Karakorams, and the terrain is known as the Trans Himalaya.

The subduction and overlapping of these two plates resulted in the thickest crust to be found anywhere on Earth - a terrain we call the Tibetan plateau, or the 'roof of the world'. The easternmost fringe of the Indian plate dove beneath the Sunda plate — this arc-shaped margin is overlaid by a thick layer of sea sediments and oceanic crust eroded from the Himalayas, transported by the Ganges and Brahmaputra rivers, and deposited as fans under the sea, thus creating the Andaman-Nicobar islands. (Read more about the Andaman-Nicobar islands and their unique biogeography)


This is the complicated geological history of Ladakh — which explains why the landscapes are as beautiful and they are, bewildering.

Ladakh's shimmering blue lakes, multi-coloured mountainscapes, glacier-sculpted valleys, and the braided, silt-heavy rivers that irrigate its summer fields, tell stories of the tectonic forces that continue to shape the landscape, and of changing climate and its effects on these margin lands. What follows are some stories of Ladakh's landscapes and landforms:



School geography taught us how mountains can stop moisture-laden clouds from reaching certain places, creating rainshadow areas. As Ladakh lies beyond the Himalaya, it falls within a rainshadow region and receives very little annual precipitation. Over millennia, these arid seasons have resulted in parched landscapes of grit and sand. Yet in recent years, changing global climates have disrupted Ladakh's seasons, and the occasional cloudburst results in sudden, terrifying flash floods.

On July 22, 2023, at midnight, a cloudburst was recorded over Ganles, a settlement nestled in the shadow of the Khardung range, a section of the lower Karakorams. Within a couple of hours, the water swirled and surged downhill from the Lungmar valley, dragging cars, uprooting trees, carrying massive boulders, and shearing away parts of house walls. The flood path split into three channels on its way, slowing down its velocity and water pooled in the open courtyard of the Chokang Vihara - a Buddhist gompa or temple in Leh market. Relief and restoration efforts began that very night, and the debris cleaning continued in the weeks after.

Two barley fields on either side of the road, which looked identical a week prior to taking this photo. Can you guess which field lay in the path of the flash flood?

When I reached Leh, a week after the cloudburst, I trailed along the flood path — the raw power of run-off water was writ large in the size of the boulders, the thick layer of sand and silt that covered people's fields and had left muddy marks on house walls and gates. I got a first-hand account of the flash flood (thanks to my mother, who has chosen to live in this cold, arid desert), and was able to imagine the scale and intensity of the event.

Most news coverage of the flash flood was reactionary: no lives lost, relief efforts underway, a list of areas affected, and political statements about aid. Yet this wasn't Ladakh's first cloud burst: there was a terrible, unexpected one in 2010 in Leh, that resulted in a flash flood. The locals dread heavy rains, as memories of that last cloudburst, with its death toll and devastation are well-remembered. There have been other cloudbursts of varying intensity in 2006, 2012, 2015, and 2018 — each, a harbinger of climate change.

Yet disrupted climate patterns and an arid, rocky terrain with soils that cannot absorb moisture well, are just part of the reason why cloudbursts in Ladakh lead to flash floods. Human development and intervention is another piece of that puzzle: population growth, the introduction of non-native, thirsty trees like poplars and willows, often planted along streams and rivers, unregulated tourism, and infrastructure development, have all played a role in exacerbating the impact of natural calamities.



Driving westwards from Leh, along the Srinagar highway, the road is a dark, hyphenated ribbon stretching through landscapes of sand, and clayey silt. The Indus river winds its way to the left (or south) of this road, and the rounded pebbles, also known as ground moraine, embedded in the chalky soil, mark the path of ancient glaciers. In places, deposits along both banks of the Indus river have also been used to reconstruct the relict, glacial Spituk lake — studying the sediments of such ancient lakes can offer insights into past climate patterns, and indicate shifts in the Indian Summer Monsoon and the Intertropical Convergence Zone. (Read more about the Indian monsoon.)

Almost forty kilometres on, the road winds along a beautiful, steep-sided V-shaped river valley, and the breathtaking confluence of the Indus and Zanskar rivers lies to the left. The locals tell of how the rivers change colours with the seasons; the Zanskar river exhibits hues of blue, and the Indus river changes from watery to chalky green. As Ladakh had experienced some rain in the weeks before I travelled there, both rivers were sediment-laden and murky.

The Zanskar-Indus confluence in winter (left - taken in November 2018), and monsoon (right - taken in August 2023).

The Zanskar river originates in the Great Himalayan range and is fed by snowmelts on its northeastward journey. This confluence marks where the Zanskar meets the Indus river as a tributary, and their flow continues as one channel that runs further southeast towards Leh. Born from mountain springs to the northeast of Mount Kailash in Western Tibet, the Indus river flowed before the Himalayan range began to fold and form along the plate collision zone, and has continued to flow, albeit along a different route, since. Rivers like the Indus that existed before the landscape around them changed due to tectonic activity or other geological processes are known as antecedent rivers. Often, antecedent rivers cut or erode deep gorges into the new topography that has been uplifted along their paths. Other Himalayan rivers like the Brahmaputra, Sutlej, and Kosi, are also antecedent rivers, characterised by deep gorges.

Follow the Indus further upstream to reach the Alchi monastery — the route is a geologist's paradise: picture-perfect fold formations, purple-green schist hills, and weathered, maroon-red turrets of clay near Basgo formed from the sediments of ancient lakebeds. Along the Indus, numerous petroglyphs - part-figurative, part-realistic rock art from prehistoric times, have been discovered. Here's an article on Ladakh's petroglyphs from Sahapedia.



With less travel time than I would have liked, my last excursion was to the Nubra valley. To the north of Leh, a road carves its way into the Khardung range, and further into a cloud-kissed, permafrost-edged landscape. Our route towards Khardung La — the world's second-highest mountain pass (5359 metres, or 17,582 ft) — retraced an ancient trade route for salt, carpets, precious stones, among other things, into Central Asia. Rough trails crisscrossed the treacherous, steep-sided, scree-covered slopes, and I imagined heavy caravans of yaks and herders inching along this route. To think that travellers in a different day and age, may have paused to take in these dramatic landscapes — sometimes aglow in stark sunlight, at others, cast into the blue-grey shadow of clouds — lent the journey a sense of timelessness.

The interplay of light and shadow en route to Khardung La.

At Khardung La, I remember thinking of how the volcanic rocks underfoot and under permafrost, were signatures of the Ladakh magmatic arc — I was straddling for a short, giddying moment, two continental blocks. Locals often advise not staying at Khardung La for more than ten minutes, the sheer altitude is enough to make you light-headed and disoriented (as I discovered when a co-passenger took a longer photography break than was ideal).

As per a local geologist, a short distance after the Khardung village, one can see the Shyok Suture. However, it wasn't clearly visible from the highway, and I suspected a small expedition would've been better. I wasn't too disappointed, the chiaroscuro landscapes continued to delight me.

As we descended further, the occasional flock of red-billed chough, or a lonely eagle (it was too far to tell which species), were the only signs of wildlife. Little wonder, there was road-widening activity happening along several stretches — huge stone-breakers, or labourer groups with shovels, worked under the blazing sun. Scraggly bouquets of yellow Artemisia, and lavender Russian sage, brightened up the rock-strewn hillsides - the vegetation and the gentle slopes indicated we were entering a valley.

As we rounded a curve in the road, an immense, flat valley yawned before us, with a small braided river channel carved its way through sand and silt. I was awestruck! I was expecting a river valley, knowing of the Nubra and Shyok rivers that flowed along this stretch, yet this was a textbook-perfect example of a glacier-carved valley. River valleys are V-shaped, narrow channels fringed by sharp slopes, whereas glacial valleys are U-shaped, broader channels with gentler slopes. This was the largest glacial valley I had ever seen!

The vast vista of the Shyok valley, just shy of Diskit town.

Later, I read how the Nubra river is a tributary of the Shyok river, which flows into the Indus, sometimes along a series of palaeolithic fault lines. Both rivers are not just fed by glaciers, their wide valleys which lie in the shadow of the jagged, metamorphic Karakoram and Ladakh ranges, have been shaped by several past and present glaciers. The glacial activity also explains why the rivers are so sluggish and braided, their flow is slowed down by the gritty or sandy sediment or moraine brought into the valley by glaciers. The sediment also supports colourful, shrubby vegetation, which had sprung up all along the sand bars, creating unique mid-channel habitats.

Further towards the Hunder or Khalsar villages, the landscape changes again — sand dunes and double-humped Bactrian camels appear like mirages on the horizon. Incredibly, these sand dunes were created by the dry fury of the wind, scouring the landscapes over millennia, whereas the sandbars of glacial sediment, are continously erode and accrete, as per the whims of seasonal rivers.

The double-humped Bactrian camels are native to Central Asia - and camel rides along the river dunes are part of Hunder's touristy offerings.

If landscapes of wind, water, and ice aren't impressive enough, you may continue deeper into Nubra valley as far as Panamik village — where a series of hot springs await! These sulfuric hot springs, located at an altitude of over 10,000 feet above sea level, emerge directly along the Karakoram fault due to geothermally heated groundwater that rises from beneath the Earth's crust.


Ladakh's landscapes hold incredible potential as geoheritage, providing striking evidence of the powerful forces that have shaped our world. As we aim for the moon (and successfully land on it), these landscapes may also serve as proxies for studying planetary geology, offering insights into the geological processes of the Moon and Mars. Yet just as Ladakh's landscapes hint at geological dramas in the past, they also speak of delicate ecological balances being undermined. As we travel through these landscapes, let us appreciate not only their beauty but also embrace the lessons they hold.


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