Explanation:

The acronym GLOF is used for glacier floods caused by the drainage of naturally dammed lakes in the glacier, on or at the margin of glaciers.

• Glacial lakes form when a glacier retreats, leaving the debris mass at the end of the glacier – the end moraine – exposed.
• The moraine wall can act as a natural dam, trapping the meltwater from the glacier and leading to the formation of a lake. The moraine dams are composed of unconsolidated boulders, gravel, sand, and silt. As with landslide dams, they can eventually break catastrophically, leading to a glacial lake outburst flood or GLOF.

Hence option 1st is correct.