As glaciers slowly move over land, their motion grinds up rock into dust. These particles form what’s known as glacial flour, or rock flour. Gravity and the sheer weight of glaciers causes them to move slowly downhill. As these large masses of ice shift, friction scours the underlying rock and ground, creating fine dust.
Glacial flour absorb longer wave colors
Eventually, much of this dust ends up traveling along with glacial meltwater into lakes. Since the particles that make up glacial flour are so fine, they tend to accumulate in the upper layer of the lakes. Known as the benthic zone, this is the layer of a lake where light penetrates. As sunlight reflects off the glacial flour particles, red, orange, and yellow (longer wave colors) in the light spectrum is absorbed. Only green and blue are reflected (shorter wave colors) – when these two mix they form the turquoise color seen in glacial lakes on satellite imagery.
Tustumena Lake
Tustumena Lake, located on the Kenai Peninsula, is Alaska’s 8th largest lake. Originating from the Harding Icefield, Tustumena Glacier feeds glacial flour in Tustumena Lake, giving this deep lake its turquoise color as seen on this Landsat 8 satellite image taken on September 20, 2024.
Turquoise lakes on South Island in New Zealand
Lake Pukaki, Lake Tekapo, Lake Ohau, and Lake Benmore on South Island in New Zealand are also known for their turquoise hues. These alpine lakes are fed by rivers that bring glacial flour runoff. Lake Tekapo is fed by meltwater from the Classen, Gray, and Godley glaciers that empty into Godley River. Lake Pukaki receives runoff from the Tasman and Hooker glaciers via the Tasman River.
Fonte : National Geographic
