Glacial Lakes

These lakes began life as large pools of glacial meltwater, and have been supplemented with rivers and rain since. At the end of the Last Glacial Maximum, glaciers began to recede in response to warming temperatures. Significant deposits of ice were left behind in the hollows of hills, which then melted and formed lakes. Glacial lakes are often accompanied by other signs of glacial activity, scoured valleys, deep striations in bedrock and other landforms which make up the surrounding landscape.

Glaciers grind rock that they flow over, turning them into sediments which form the bottom of the lake. On occasion, the result is so fine and silt-like that it is called glacial flour. When it becomes suspended within the water, it gives it a unique, sometimes milky colour along with a greenish tinge because of the algae which thrive in such mineral-rich water. Lakes formed by ice can be told apart from those formed by water. The banks of glacial lakes are irregular and jagged, reflecting how glaciers carve out a path through land, but lakes with origins in liquid water have smooth shores and are interconnected with rivers more often.

Where the glacier has been can be told from the sediments deposited within the lake, as glaciers are capable of transporting material far from where it originally lay. As sediment varies with location, it affects the water’s mineral content. Animal activity also leaves trace elements, which then go into forming layers of sediments at the bottom metres thick. Glacial lakes can be studied in this way by analysing these layers and their chemical composition; useful details may be found on dates and manner of formation, as well as recent changes and impacts on the lake.

Further reading on the dangers glacial lakes can be:
http://www.theuiaa.org/bursting_glacial_lakes_in_nepal.html