Two lakes separated by a likely moraine photographed from orbit in Patagonia
An astronaut aboard the International Space Station photographed Lakes Pueyrredón and Posadas in Argentine Patagonia on September 15, 2020. The lakes are separated by a narrow strip of land. In the image, the bodies of water have distinctly different colors: the deep Lake Pueyrredón appears dark blue, while the smaller Lake Posadas is turquoise, Live Science reports.
It was once a single body of water
Lake Pueyrredón is the Argentine part of a glacial lake about 65 kilometers long that extends across the border into Chile. Its Chilean section is called Lake Cochrane. The water in both parts of the lake is clear, and the maximum depth reaches about 500 meters, which gives Pueyrredón its rich blue appearance.
Thousands of years ago, a thick barrier of deposits formed in the southern part of Pueyrredón, resulting in the formation of Lake Posadas. It is about 8 kilometers long. Its lighter water color is attributed to its shallower depth and the significant inflow of river sediments from a nearby river.
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Traces of a glacier and river deposits
On the western shore of Lake Pueyrredón, several rivers formed three fan-shaped deltas. They increase in size from north to south. Wind, currents, and waves moved some of the deposits from the edges of the two smaller deltas, forming long, narrow sand spits.
The strip of land between Pueyrredón and Posadas resembles such spits. At the same time, according to NASA's Earth Observatory, it is most likely a moraine — a barrier of sediment and large rocks formed along the edge of an iceberg or an ancient glacier. Both lakes lie in a large valley that was once carved out by an ice sheet covering the area.
