Moraines, GLOFs and Hindu Kush Himalaya, Situation in Sikkim, Important Glacial Lakes in Asia (Download PDF)

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Glacial Lake Outburst Floods

  • A sudden release of water from a lake.

  • Also known as GLOF.

  • This is being fed by glacier melt that has formed at the side, in front, within, beneath or on the surface of a glacier.

  • Nearly 200 glacial lakes surround the Himalayan states, Uttarakhand, Himachal Pradesh and Jammu Kashmir.

Rapidly Expanding Glacial Lakes

Rapidly Expanding Glacial Lakes

Rapidly Expanding Glacial Lakes


  • Glacially formed accumulation of unconsolidated glacial debris.

  • In simple terms moraines can be defined as accumulations of dirt and rocks that have fallen onto the glacier surface.

  • Occurs in both currently and formerly glaciated regions on Earth.

  • In a nut shell they play a crucial role in Glacial formation.

Lateral moraines,Medial moraines,End moraines,Terminal moraines

Lateral moraines, Medial moraines, End moraines, Terminal moraines

Lateral moraines, Medial moraines, End moraines, Terminal moraines

Lateral Moraines

  • Parallel ridges of debris.

  • These get deposited along the sides of a glacier.

  • They also protect the ice under them from the elements.

  • With the advancement and retreats multiple lateral moraines may develop.

Ground Moraines

  • Till-covered areas with irregular topography.

  • No ridges.

  • Gets accumulated at the base of the ice.

  • May also get deposited as the glacier retreats.

  • May be modified into drumlins by the overriding ice.

  • A drumlin is an elongated hill in the shape of an inverted spoon or half-buried egg.

Rogen Moraines

  • Also known as ribbed moraines.

  • A type of basal moraines.

  • These moraines have been named after Lake Rogen due to the landform’s type locality.

  • They look like tiger stripes on aerial photographs because of the depressions between the ribs that are sometimes filled with water.

Terminal Moraines

  • Ridges of unconsolidated debris.

  • Deposited at the snout or end of the glacier.

  • Mark the maximum advance of the glacier.

  • These moraines may get destroyed by postglacial erosion.

Recessional Moraines

  • Small ridges left as a glacier pauses during its retreat.

  • Often observed as a series of transverse ridges running across a valley.

  • Perpendicular to the lateral moraines.

  • Created during temporary halts in a glacier’s retreat.

Medial Moraine

  • A ridge of moraine that runs down the center of a valley floor.

  • Forms when two glaciers meet.

  • The debris on the edges of the adjacent valley sides join.

  • Carried on top of the enlarged glacier.

Supraglacial Moraines

  • Created by debris accumulated on top of glacial ice.

  • Accumulation of debris due to ice flow.

Washboard Moraines

  • Also known as minor or corrugated moraines.

  • Low-amplitude geomorphic features caused by glaciers.

  • It resembles a washboard from the air.

Veiki Moraine

  • A kind of hummocky moraine.

  • Forms irregular landscapes of ponds and plateaus surrounded by banks.

  • Is common in northern Sweden and parts of Canada.

GLOFs and the Hindu Kush Himalaya

  • Moraine-dammed glacial lakes are common.

  • Numerous GLOF events have been traced back resulting in the failure of moraine dams.

  • With the rising volume of the glacial lake, the pressure on the dam containing it also rises.

  • They remain a persistent threat to downstream communities and infrastructure.

  • With the rise in temperature new lakes form, existing ones expand and sometimes merge.

  • The potential flood volumes in the high mountains also increase with the increase in temperature.

Other reasons responsible for GLOF:

  • Fragmentation of the source glacier

  • Fragmentation of landslides

  • Internal processes (For eg water seeping through the structure)

  • Changing climate

Glacial lakes and flooding

Glacial lakes and flooding

Glacial lakes and flooding

Causes for Melting Glaciers

  • Global warming.

  • Rampant environmental pollution along the Himalayan plains.

  • Human activities like burning of fossil fuels, oil and gas drilling, deforestation.

Consequences of Melting Glaciers

  • Influences the Indian summer monsoon.

  • Frequent GLOF s are causing huge casualties and loss to local infrastructures.

  • Biodiversity loss

  • Increased glacial melting

  • Loss of the environmental services

Situation in Sikkim

  • Several lakes have been formed due to melting of scores of glaciers in the Himalayan region.

  • The number of glacier lakes is further expected to increase due to global warming.

  • At the sametime, the size of the existing glacier lakes is also expected to expand further.

  • Huge amounts of water are flowing from the North Lhonak glacier.

  • The inflow from the North Lhonak glacier is almost same as what South Lhonak Lake is discharging.

  • The South Lhonak Lake has grown many folds since 1960s with a history of bursting.

Steps Taken by Sikkim to Control GLOFs

  • Installation of water level sensors at South Lhonak Lake.

  • Whenever there is sudden fluctuation in water level, this sensor gives the water level of the lake.

  • Three pipelines have been installed which are discharging water at the rate of 50 to 60 litres per second each.

  • Transporting the pipes to high altitudes poses serious challenge.

  • Further the way to the lake is full of steep and narrow passages.

  • Yaks were being used to carry the pipes and other materials to the lake situated at 17,000 ft as they can only carry the pipes safely to the destination.

Glacial lake,Future lake and South Lhonak lake

Glacial lake, Future lake and South Lhonak lake

Glacial lake, Future lake and South Lhonak lake

Some Important Asian Glacial Lakes

  • Imja Tsho, Nepal

  • Tsho Rolpa, Nepal

  • Dudipatsar, Northern Pakistan

  • Ratti Gali Lake, Kashmir region

  • Katora Lake, Pakistan

  • Merzbacher Lake, East Kyrgyzstan

  • Tsongmo Lake, East Sikkim (India)

  • Karambar Lake, Khyber Pakhtunkhwa Pakistan

  • South Lhonak lake, North-Western Sikkim (India)

  • Zrebar Lake, Western Iran

  • Rush Lake, Gilgit-Baltistan, Pakistan

- Published/Last Modified on: June 2, 2020


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