The NOAA-20 VIIRS instrument captured a rarely seen plume of high-latitude dust off the coast of Greenland on October 14, 2018. This very fine powder known as “glacial flour” forms when glaciers weighed down by rocks scrape over bedrock.
The National Snow and Ice Data Center notes that glacier flour, also known as rock flour, is often flushed out in meltwater streams and causes water to look powdery gray. When water levels are low, the flour dries out on riverbanks and deltas. Winds then lift the dust into the air and can transport it over several hundred miles of open ocean.
This dust event, according to the CIMMS Satellite Blog, likely originated from a glacial outlet between Qeqertarsuatsiaat and Paamiut, which are both settlements in southwestern Greenland located along the Labrador Sea.