File:Rio de la Plata (MODIS 2021-09-22).jpg

English: This stunning true-color image captures the dramatic colors created by the mixing of muddy river water with the clear, but saline water of the South Atlantic Ocean. This mixing occurs in Rio de la Plata, the muddy estuary of the Paraná and Uruguay Rivers, which forms part of the border between Argentina and Uruguay. The rich estuary supports both capital cities of Buenos Aires, Argentina and Montevideo, Uruguay. These cities appear as gray pixels on the south shore and the north shore of Rio de la Plata. Buenos Aires is the larger city.

The Paraná is South America’s second longest river and drains much of the southeastern part of the continent. The extensive delta of the Paraná nearly reaches across the mouth of the Uruguay River. The rivers’ fertile soils support extensive agriculture, including livestock, in the region surrounding the cities. As the rivers course through the landscape, they accumulate large amounts of sediment, which dumps into the estuary along with fresh water. The complex mixing pattern creates beautiful colors, with sediment floating near the surface appearing in shades of tan. As sediment sinks below the surface, the reflectivity changes and this causes the color to trend towards green when seen from space.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired this true-color image on September 16, 2021, in the waning days of winter.