ISS013-E-78506 (7 Sept. 2006) --- Sand dunes near Mongolia's Har Lake are featured in this image photographed by an Expedition 13 crewmember on the International Space Station. Har (or Black) Lake is located in the western part of the country within the Valley of Lakes--part of a system of closed basins that stretches across central Asia. According to scientists, these basins are the remnants of larger paleolakes that had begun to shrink in size by approximately five thousand years ago as regional climate became drier. Today, the Valley of Lakes is an important ecological resource for study of steppe grasslands, and as resting points for large numbers of migratory birds. Portions of the basin are designated as national parks or other protected areas, and Har Lake itself is an ecotourism destination (usually by horseback). This oblique view captures the dynamic nature of the landscape of Har Lake. The lake is encircled by sand dune fields which encroach on the lower slopes of the Tobhata Mountains to the west and south. Gaps in the mountains have been exploited by sand dunes moving eastward (indicating westerly winds) -- the most striking example being a series of dunes entering Har Lake along its southwestern shoreline. Here, the dune forms reflect the channeling of winds through the break in the mountain ridgeline, leading to dune crests oriented transverse to northwesterly winds. Another well-developed line of dunes is visible between Har and Baga Lakes. While these dunes appear to cut across a lake surface, the dunes have in fact moved across a narrow stream channel.