The most striking feature of the image mosaic is the intricate ice block pattern on the lake surface. The maximum dimensions of the lake are 31 kilometers by 14 kilometers (1 kilometer is about 0.6 miles), indicating that the ice blocks range from less than ten to hundreds of meters in diameter. The ice pattern is caused by repeated cycles of freezing, fracturing, and refreezing of the ice due to variations in temperature and wind-induced ice motion. A prominent white linear feature extending north-south across the center of the lake is suggestive of an ice ridge formed by east-west winds subsequently highlighted by snow. Similar features are visible along the eastern and southern shorelines and in the southwestern portion of the lake. Records from the nearest weather station to Lake Puma Yumco (approximately 140 kilometers to the northeast at Llasa, Tibet) indicate that daily day-night temperatures varied on average from -7 to 14 degrees Celsius (about 19 to 57 degrees Fahrenheit) during the week preceding acquisition of the astronaut photographs.