Geography · 4 Sep 2026

Glacial Lake Outburst Flood

Consider the following statements regarding recent Himalayan mass-movement disasters:

  1. The 2023 South Lhonak glacial lake outburst flood affected the Teesta river valley in Sikkim.
  2. The 2021 Chamoli disaster in Uttarakhand was caused by the breach of a moraine-dammed glacial lake.
  3. The Himalaya is a geologically young, still-rising mountain system, making it inherently prone to mass-wasting events.
A1 only
B3 only
C1 and 3 only
D1, 2 and 3
This question is based on: Nepal's Flash Floods Show the Himalaya Sending an Old Warning, Faster Than Ever
Take this in full test mode → Instructions for 4 Sep 2026
About this question

Why in news

A devastating flash flood in Nepal on August 26, 2026 (death toll crossing 1,243) has revived comparisons with the 2021 Chamoli and 2023 Sikkim disasters as recurring examples of Himalayan mass-movement events.

Why for UPSC

UPSC frequently tests the distinction between different types of Himalayan mass-wasting disasters (GLOF vs rock-ice avalanche) rather than the headline event itself, checking whether aspirants understand the underlying physical mechanism.

Prelims summary

GLOFs occur when glacial lakes (often moraine-dammed) breach suddenly, as in Sikkim's South Lhonak (2023); this differs from rock-ice avalanches like Chamoli (2021), where a mass of glacier and rock detaches directly. Both are driven by the Himalaya's young, unstable geology and accelerating glacial retreat.

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