Himalayan Valleys, Snowline and Glaciers

At a Glance

• Kashmir valley Synclinal basin; karewas on its sides
• Karewas Lake deposits; saffron, almond, apple
• Snowline Lower in the west and on wetter slopes
• Siachen Glacier About 70 to 76 km; longest in the Karakoram
• Gangotri Glacier About 30 km; source of the Bhagirathi
• Exam link UPSC Prelims, Geography: India: Location, Geology and the Himalayas

Where Does It Fit?

This is the seventh topic of the macro on India’s location, geology and the Himalayas. The previous topic divided the Himalayas by region, and this one describes their valleys, snow and ice. The last topic of the macro covers the passes. Previous topic: Regional Divisions of the Himalayas. Next topic: Passes of the Himalayas and Their Significance.

What Are the Important Valleys of the Himalayas?

The karewas are flat-topped mounds of lake deposits that fringe the Kashmir valley on all sides, up to about 1,400 m thick, with clay, sand and silt, fossils of mammals and layers of peat. During the Pleistocene, about a million years ago, the whole valley was a lake. Uplift opened the gorge at Baramulla, and the lake drained, leaving the karewas, which were then cut by the Jhelum and its tributaries. The karewas are used for saffron at Pampore, and for almonds, walnuts, apples and other orchards, which is an example of how a geological feature supports a regional economy.

What Is the Snowline?

The snowline is the lowest level at which snow lies throughout the year, below which it melts in summer. It depends on three things: latitude, because the line is lower at higher latitudes; precipitation, because greater snowfall allows snow to survive at lower levels; and slope and aspect. In the Himalayas the line is lower in the western Himalaya and Karakoram, which lie at higher latitudes (up to about 36 degrees north), than in the east. It is also lower on the southern slopes of the Greater Himalaya, which receive more snow from the monsoon and western disturbances, than on the drier northern slopes. Older textbooks quote about 2,500 m in the west and 3,500 m in the east for the lower limit of snow cover, but the permanent snowline, which is the level of glacier ice, is much higher, at well over 4,000 m in most regions. A rise in the snowline is one of the most direct indications of warming in the mountains, as in Heat Transfer and Heat Budget of the Earth.

What Are the Himalayan Glaciers?

• Number and area: the Himalayas have about 15,000 glaciers, and are called the Third Pole, because they hold the largest store of ice outside the polar regions. The greatest concentration is in the Karakoram.
• Siachen Glacier: in the Nubra valley of Ladakh, about 70 to 76 km long, the longest glacier of the Karakoram and among the longest outside the polar regions, second only to the Fedchenko in the Pamirs, which is about 77 km. Older textbooks call Siachen the longest, but later measurements place Fedchenko first. The Hispar in the Karakoram is another large one.
• Pir Panjal glaciers: smaller and fewer, such as the Sonapani glacier in Lahaul, only about 15 km long.
• Gangotri Glacier: about 30 km long, in Uttarakhand, the source of the Bhagirathi, which becomes the Ganga at Devprayag. Others in the region are the Pindari and Milam glaciers.
• Eastern Himalaya: the Zemu glacier at Kanchenjunga in Sikkim is the main example.

The glaciers regulate river flow by storing water as ice in the winter and releasing it during the dry summer, as in Ganga River System. Most Himalayan glaciers are retreating. The 2023 assessment of the Hindu Kush Himalaya by ICIMOD found that ice there is melting faster than before and warned of large losses by the end of the century if emissions are not controlled, though the Karakoram glaciers have shown stability in some studies, called the Karakoram anomaly. The retreat creates glacial lakes held back by loose moraine, which can burst in a glacial lake outburst flood. Recent examples are the 2013 Kedarnath disaster, caused by extreme rain together with a breach of the Chorabari lake; the Chamoli disaster of February 2021, caused by a rock and ice avalanche; and the October 2023 flood from the South Lhonak lake in Sikkim, which destroyed the Teesta III dam. As an analytical point, the Himalayan cryosphere links the health of the glaciers to the water security of hundreds of millions of people downstream, and to the safety of the hydropower and settlements in the valleys, so monitoring of the glacial lakes and the regulation of construction in the valleys are urgent.

Why Is This Topic Important?

• Facts Karewas and glaciers asked
• Hazard GLOF and Chamoli
• Water Glacier-fed rivers

What Came Next?

The last topic of the macro describes the Himalayan passes and their significance. Next topic: Passes of the Himalayas and Their Significance.

Key People and Terms

• Karewa Lake deposit mound in Kashmir
• Snowline Limit of permanent snow
• Moraine Debris carried by a glacier
• GLOF Glacial lake outburst flood
• Cryosphere Ice and snow part of the Earth system
• Third Pole Himalaya-Tibet ice store

Exam Corner

Mains Angle

Questions link glaciers to climate change and disasters. These points add depth.

• Water Storage and regulation
• Hazard GLOF
• Response Monitoring and land use