Lake Erepecu and Rio Trombetas in Brazil are featured in this sun glint image photographed by an Expedition 20 crew member on the International Space Station.
The 38 kilometers long Lake Erepecu runs parallel to the lower Rio (river) Trombetas which snakes along the lower half of this photograph. Waterbodies in the Amazon rainforest are often so dark they can be difficult to distinguish. In this image, however, the lake and river stand out from the uniform green of the forest in great detail as a result of sun glint on the water surface. Sun glint is light reflected off of a surface directly back towards the viewer, in this case a crew member onboard the space station. Soil color beneath the forest is red, as shown by airfield clearings near Porto Trombetas (upper left), a river port on the south side of the Trombetas River.

The Trombetas flows into the Amazon River from the north about 800 kilometers from the Amazon mouth. Despite being so far from the sea, seagoing ore ships export most of Brazil?s bauxite from Porto Trombetas. Bauxite is the raw material formed in these tropical soils for the production of aluminum (the Trombetas bauxite mine is outside the upper margin of the image). Central Amazonia has many lakes like Erepecu?relatively straight, large waterbodies located just off the main axis of the large rivers. These lakes, as distinct from smaller floodplain lakes next to the large rivers, were created as rivers cut down during the repeated low global sea levels of the recent geological past (according to scientists, related to the ice ages of the last 1.7 million years). River water filled the valleys to form lakes during intervening periods of high sea level.

Many larger rivers like the Trombetas and Amazon carried enough sediment to fill their immediate valleys?rivers flowing in unconsolidated sediment produce sinuous courses like those along the upper part of the image?but not enough to fill tributary valleys further from the axis of flow, so that lakes like Erepecu are formed. less

Date Created: 2009-08-25
Center: JSC

NASA ID: iss020e034693
ISS020-E-034693 (25 Aug. 2009) – Photographer: Robert Thirsk Larger image