Description: The alpine lakes of the Tibetan Plateau are some of the most remote in the world. This mosaic of astronaut photographs, taken along a single International Space Station orbit track, depicts Lake Puma Yumco during the winter season. The lake is located at an elevation of 5,030 meters above sea level (16,503 feet), and is considered ultraoligotrophic, meaning that nutrient concentrations in both the water column and lake sediments are extremely low. Water in such lakes tends to be blue to blue-green and to have high clarity due to low levels of photosynthesizing organisms such as phytoplankton. Color change in these lakes is usually due to shallowing of the water—blue indicating deeper water. A depth transition is visible along the west-southwest shoreline of Lake Puma Yumco at the lower left of image.