A striking image captured by an astronaut aboard the International Space Station on September 15, 2020, reveals a unique geological formation in Patagonia where two distinctively colored lakes are divided by a narrow strip of land.
Located in Argentina near the coordinates -47.42, -71.88, the scene showcases Lake Pueyrredón on the left and the smaller Lake Posadas on the right. Lake Pueyrredón constitutes the Argentine portion of a massive 40-mile (65-kilometer) glacial body of water that extends across the border into Chile, where it is known as Lake Cochrane. Both segments feature crystal-clear depths reaching up to 1,600 feet (500 meters), giving Pueyrredón its characteristic deep blue appearance when viewed from orbit.
The formation of Lake Posadas dates back thousands of years, when a thick sediment barrier emerged across the southern section of Pueyrredón. Approximately 5 miles (8 km) long, this newer, shallower body of water appears lighter and teal due to a significant influx of sediment from nearby rivers, according to NASA’s Earth Observatory.
Additional rivers originating from adjacent hills have deposited large quantities of sediment along the western shoreline of Lake Pueyrredón, forming three fan-shaped deltas that increase in size from north to south. Wind-driven currents and waves have subsequently eroded sediment from the outer edges of the two smaller deltas, creating elongated sandspits that point down-current.
While the landbridge separating the two lakes resembles these sandspits, experts identify it as a moraine—a ridge of debris formed along the edge of a glacier or large iceberg. The lakes sit within a valley carved by a colossal ice sheet, with the last remnants of this ancient ice located approximately 20 miles (30 km) west of Lake Cochrane.
Despite being largely uninhabited, the region attracts tourists for camping, hiking, fishing, and kayaking. A narrow airstrip is visible on the smallest delta, running parallel to its sandspit. Nearby, Lake Posadas features a famous rocky arch on one of its islands, a popular spot documented by travelers.
This imagery highlights Patagonia’s diverse geography, which includes mountains, fjords, deserts, and rainforests. The area contains dozens of similar valleys and fjords sculpted by the same ice sheet that once dominated the landscape.
I’ve kayaked in Lake Posadas and never noticed the clarity there. Does it really look that teal from orbit?
Wait, so the ‘strip of land’ is actually a glacial moraine? That explains the ridge shape perfectly.
The color difference is absolutely stunning! It’s amazing how sediment can completely change a lake’s appearance from above.