Story of the 45 Million Year Old Ladakh Plateau

Ladakh is the northernmost region of India and over the years, has become a favorite among travelers who visited this place or wish to come for adventure holidays. It lies within the state of Jammu and Kashmir and is an expansive cold desert-cum-plateau; most of it lies over 10000 feet above sea level. The plateau is bordered by the Himalayas in the south and Karakoram Mountains in the north; the Ladakh and Zanskar ranges are also part of the region. To its south, Ladakh has a heavily glaciated landform, from where most of the rivers of Jammu and Kashmir originate. The Ladakh mountain range is of moderate elevation and does not contain any significant peaks. It is only beyond Zoji pass that the altitude increases and crosses the 23000-feet mark. The Indus, Shyok, Zanskar, Suru and Nubra Rivers drain the plateau and form their separate valleys here.

Mostly below 10000 feet altitude, Suru Valley is among the most fertile areas here. The majority of the valley of the Zanskar River lies above 11000-feet and is connected to the rest of the Himalayan area by mountain passes. Most of the peaks in the Karakoram Range, which borders Ladakh in the northwest, are 24000 feet in height.

General Geomorphology of the Region

The mountains in the north-eastern part of the desert expose an underdeveloped formation called Ladakh batholith, which belongs to the Miocene age. A batholith is formed inside the crust of the Earth due to the cooling of magma, and it is exposed because of erosion. On the other hand, the Zanskar range presents meta-sedimentary origin, dating to the late Miocene or Palaeocene age. They were formed when the already-existing sedimentary rocks underwent a change in their geology due to metamorphism. When a part of Gondwanaland collided with Laurasia, it gave rise to what is now called Choksti Thrust. The phenomenon played an important role in the formation of gorges in the north-western and south-western parts of the desert.

Leh Valley: Geomorphology

A major part of the plateau comprises of the valley where Leh, the administrative centre of the region and a popular vacations spot is located. It contains many structures that were formed after the glaciers started melting like moraines, sand-sheets, duns, palaeolakes and alluvial fans. The valley is sandwiched between the Ladakh Mountains to the north and Zanskar range to the south. While studying its geomorphology, the formations of the valley are grouped into three sub-types. They have varied origins and exhibit glacial, fluvio-glacial, aeolian, mass-wasting and lacustrine formations. The first subtype is a high ground to the northwest of the valley, and it slopes towards the south-eastern direction. Subtype two comprises triangle-shaped formations with gentle slopes, and they are bordered by hills on three sides. The last type makes up a large chunk of the Leh valley, and it lies in a naturally-formed depression. Mass-movement, a process in which sand, rocks and soil slide down slopes, led to the formation of cone-shaped deposits called alluvial fans, along the foothills of the Zanskar Mountains. Aeolian deposits, formed due to erosion of the surface by wind; and Lacustrine surfaces, formed by sediment brought by rivers, are also well-preserved along the slopes and in the valley.

Glacial Formations

  • Transverse Mountain Valleys

Transverse mountain valleys in the Ladakh range and those along the Zanskar Mountains show different effects of the same natural processes. The former are a result of glacial processes, while the latter owe their existence to mass-wasting. These ranges have steep slopes, rocky peaks and small valleys at 18400-feet altitude and above. Less snow accumulates in the vertically aligned and elongated Leh and Phyang valleys and hence, no glaciers are formed here. Contrary to this, the northern slopes of the Ladakh range have zones that allow snow to accumulate and glaciers to flow. Alluvial fans in the valleys of the Zanskar region are formed due to the glaciers that arise in the mountains and flow southwards.

  • Amphitheatre Valleys

These formations are triangular and funnel-shaped, and steep rocky slopes border them on three sides. Their formation was a result of the deposition of sediments by melted glaciers. They have narrow tops, which join with those of mountainous valleys further upstream along rivers. Likewise, their wide edges slope down and join the surface of the Leh valley. As their area increases along with the rise in the area of the drainage basin, it has been concluded by researchers that their origins lie in glacial after-effects.

  • Moraines

Moraines are parallel ridges, formed along the lengths of glaciers due to the deposition of debris. In the region, they are found at four altitude ranges: 11100-12430 feet, 12800-14300 feet, 15390-15700 feet and 16900 feet. The majority of the 13 identified moraines are found between elevations of 11100 feet and 12430 feet above sea level. Their width varies from 300 feet to 450 feet, and they occur as discontinuous ridges, stretching for a few kilometres in length. These sediments are composed of cobblestones, gravel, boulders and pebbles embedded within each other.

Mass-Wasting Formations

This vast cold desert experiences great variations in temperature that results in the breaking of rocks. Along the mountain slopes, pebbles and gravel are brought down by rivers, and both these factors lead to occurrence of scree slopes.

  • Bajada

These alluvial deposits are quite small and studies say that the formation of the valley restricts their expansion. They are large in the centre of the region, and they decrease in size towards the gorges. Those, along the foothills of the Zanskar Mountains, are a result of persistent mass-wasting. Along the southern banks of river Indus, exposed sedimentary and alluvial deposits are seen. Their size varies from those of boulders, cobblestones, pebbles and clay to that of sand particles.

  • Aeolian and Lacustrine Structures

If travellers are taking tours through Ladakh, they are bound to see dunes and sand-sheets that are well preserved. In Spituk, Shey and Gumpuk, visitors will find numerous lakes of glacial origins, formed in the depressions between the dunes and hill-slopes. The gravelly formations in Spituk correspond to the meta-sedimentary formation of the Zanskar range, while their sands shows effects of wind erosion, and the silt shows glacial sedimentation. This silty nature also means that they were derived from mountain slopes, and they were exposed there due to the seasonal drying of glacial lak

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