The above image, acquired by the Operational Land Imager (OLI) on Landsat 8 on November 3, 2021, shows two of the three great lakes, along with Cedar Lake, in south-central Manitoba. (Note that Norman Kuring, a retired researcher from NASA’s Ocean Biology group applied color-filtering techniques to the image to draw out the fine details in the water. Those features are real but might not be as apparent to the unaided human eye.)

The colorful swirls in the relatively clear and shallow lakes—Lake Cedar’s maximum depth is about 10 meters (32 feet)—are likely due to suspended sediment and phytoplankton. The lakebeds are covered in fine-grained silt, clay, and calcium-carbonate sediments, which give some of the lakes their chalky blue hues. (Little Limestone Lake stands out.) The region is underlain by dolomite, a calcium-magnesium-carbonate rock similar to limestone that was deposited during the Paleozoic Era when the landmass was under a shallow, tropical sea.