The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite and European Space Agency’s Sentinel-2 collected captured a large glacier flour storm that occurred on September 29, 2018. Related: What are glaciers?
What is Glacier Flour?
Glacier flour is a fine silt created by the friction of glacial movement pulverizing rock into fine particles.
When winds in Greenland are strong enough, they can carry large plumes of glacier flour that have collected on the floor of dried out floodplains.
Glacier Flour in Greenland
The satellites captured events surrounding a braided stream valley located 130 kilometers (80 miles) northwest of Ittoqqortoomiit, a village at a latitude of 73 degrees North.
Located along Greenlands’ east coast, the winds generated a large silt plume from the floodplain that empties into Scoresby Sound.
The silt likely originated from glacier activity farther up on the valley. The silt was then carried into the floodplain by meltwater streams.
During the fall, the floodplains dried out, leaving behind glacier flour. A strong wind storm on September 29 scoured the floodplain floor, lifting the silt and spreading it along the coast.
Glacial Flour Turns These Lakes Turquoise
These lakes in New Zealand’s South Island appear turquoise as seen in this Landsat 8 satellite image. Lake Pukaki, Lake Tekapo, Lake Ohau, and Lake Benmore are a much lighter turquoise color compared to the darker blue hues of Lake Wanaka and Lake Hāwea.
The reason for this is glacial flour.
Due to the fineness of the glacial flour sediment, it is easily transported and suspended in water. It is responsible for the hazy or milky look of glacier-fed streams, rivers, and lakes. Glacier lakes can exhibit a variety of stunning colors as a result of sunlight scattering as it strikes sediment particles in the water.
The fine silt that makes up glacial flour can be found in the water columns of these four lakes. The silt absorbs violet and indigo wavelengths and the water absorbs reds, oranges, and yellows from sunlight hitting the lakes. Only greens and blues are refracted.
Voiland, A. (2018, October 17). Glacier flour in Greenland skies. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/92891/glacier-flour-in-greenland-skies
Voiland, A. (2019, May 20). How glaciers turn lakes turquoise. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/145055/how-glaciers-turn-lakes-turquoise