An astronaut took this photograph of muddy floodwaters and distributary channels in the northern sector of the Tsiribihina River delta on Madagascar’s west coast. It was taken in April 2015 from the International Space Station.
Delta distributaries (channels and streams) have two morphologies: large and relatively straight or small and highly contorted. In the photo, brown sediment has been stirred up by heavy rains; when it reaches the sea, it is swept north (to the left in this image) by local ocean currents. Clearer blue water is visible to the lower right (south). Over thousands of years, the sediment supplied by the river has been shaped by waves into beach ridges along the shoreline. Those ridges appear as many parallel lines, with each line representing a prior coastline on this fast-changing (geologically speaking) coast. The oldest coastline lies furthest inland.
Four cyclones hit Madagascar in the first four months of 2015. Heavy floods followed a mid-January storm and affected not only the 50 kilometer (31 mile) shoreline of the delta but also the lower 75 kilometers (47 miles) of the river.
References & Resources
Astronaut photograph ISS043-E-101832 was acquired on April 12, 2015, with a Nikon D4 digital camera using a 1150 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 43 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by M. Justin Wilkinson, Texas State University, Jacobs Contract at NASA-JSC.
