Stock Photo - EARTH Madagascar -- 12 Apr 2015 -- 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. 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 -- Picture by Atlas Photo Archive/NASA.