"WWA Study Links Nepal Flash Floods to Rock-Ice Avalanche and Climate Change"
Compound crisis
a disaster caused by multiple interacting climatic and geological factors, not a single trigger event.
Permafrost
permanently frozen ground and bedrock; thawing removes structural support from fractured mountain rock.
The Himalayas are geologically young fold mountains. Their rocks are loosely consolidated, slopes are steep, and the region sits on active seismic zones. These physical conditions produce characteristic features: deep gorges carved by fast-flowing rivers, U-shaped and V-shaped valleys, parallel mountain ranges, and steep gradients that make slopes inherently prone to failure. This geological youth is the structural foundation for all Himalayan hazards, including avalanches, landslides, and glacial floods. By contrast, landslides in the Western Ghats are driven by a different set of factors: heavy monsoon rainfall saturating laterite soils, deforestation removing root-binding, and gentler but deeply weathered slopes. The Himalayan hazard profile is fundamentally different because seismic activity and glacial processes are added to the mix.
Glaciers are a defining feature of the high Himalaya. They feed the region's major river systems: Bandarpunch glacier feeds the Yamuna, Bara Shigri glacier feeds the Chenab, and the Siachen glacier feeds the Nubra, a tributary of the Indus. As these glaciers retreat, two processes unfold simultaneously. Meltwater volume increases in the short term, raising flood risk. Over the longer term, the structural support that glacial ice provides to surrounding rock walls is removed, destabilising the mountain face itself. Permafrost, permanently frozen ground and bedrock, acts as a natural cement holding fractured rock together. When permafrost thaws, that cement is lost.
A Glacial Lake Outburst Flood (GLOF) is one well-known consequence of glacial retreat: a lake dammed by ice or moraine breaches suddenly, releasing millions of cubic metres of water and debris. But the Nepal disaster studied by the World Weather Attribution (WWA) group represents a related but distinct hazard, a rock-ice avalanche that itself generated the flood, rather than a lake breach. Understanding this distinction matters for hazard mapping and early warning design.
The WWA study reconstructed the sequence of events at Langtang Lirung peak in Nepal. An estimated 110 million cubic metres of rock and ice detached from the mountain's northern face, tearing off an area of 2.2 sq km to a depth of 50 metres. The mass fell approximately 1,400 metres from a height of 5,150 metres. The impact on the valley floor registered as a seismic shock of 5.2 magnitude. As the debris moved, it eroded additional material from the valley bottom, including buried glacier ice, increasing its total volume. The debris flood reached Gyirong Port in Tibet in just seven to eight minutes, travelling at an average velocity of 170 km/h.
The study introduced the concept of a compound crisis to describe what caused this event. No single factor was sufficient on its own. The contributing factors included: glacier thinning (the Langtang Lirung glacier has been losing mass at roughly half a metre per year for decades, with recession accelerating from 0.5% per year over the previous two centuries to 1–2.3% per year since 2010); thawing of permafrost within rock fractures; elevated temperatures and increased meltwater; and the possible pre-conditioning of the slope by the 2015 Nepal earthquake (7.8 magnitude), which may have weakened the rock mass, though its specific contribution was not confirmed. …
When you travel in Himalayas, you will see the following:
1.Deep gorges
2.U-turn river courses
3.Parallel mountain ranges
4.Steep gradients causing land-sliding
Which of the above can be said to be the evidences for Himalayas being young fold mountains?
Consider the following pairs:
Glacier — River
1.Bandarpunch — Yamuna
2.Bara Shigri — Chenab
3.Milam — Mandakini
4.Siachen — Nubra
5.Zemu — Manas
Which of the pairs given above are correctly matched?
Differentiate the causes of landslides in the Himalayan region and Western Ghats.
Consider the following glacier-river pairings:
1.Bandarpunch — Yamuna
2.Bara Shigri — Chenab
3.Milam — Mandakini
4.Siachen — Nubra
5.Zemu — Manas
Which of the pairs given above are correctly matched?
Which of the following features observed in the Himalayas serve as evidence that they are geologically young fold mountains?
1.Deep gorges
2.U-turn river courses
3.Parallel mountain ranges
4.Steep gradients causing landslides
Select the correct answer using the code given below:
Consider the following pairs:
Peak — Mountain Range
1.Namcha Barwa — Garhwal Himalaya
2.Nanda Devi — Kumaon Himalaya
3.Nokrek — Sikkim Himalaya
Which of the pairs given above is/are correctly matched?
Consider the following statements regarding the causes of the Nepal rock-ice avalanche studied by the World Weather Attribution (WWA) group:
1.Permafrost thaw within rock fractures removed structural support from the mountain face.
2.The 2015 Nepal earthquake was confirmed as the primary cause of slope failure.
3.The zero-degree isotherm is rising at approximately 100 metres per decade due to climate change.
4.The Langtang Lirung glacier's recession rate has remained constant over the past two centuries.
How many of the above statements are correct?
With reference to the World Weather Attribution (WWA) group, consider the following statements:
1.It is an intergovernmental body under the United Nations Framework Convention on Climate Change (UNFCCC).
2.It analyses and communicates the possible influence of climate change on extreme weather events.
3.Its studies use climate models, observed temperature trends, and glacier data.
Which of the statements given above is/are correct?
Want the full note, Prelims Facts & MCQ answers?
Create a free account — takes less than a minute.
Create free account