"The crater lakes hold such huge volumes of water in comparison to the surrounding glacial lakes that they're slower to respond to temperature changes," explained Reinhard Pienitz, a freshwater lake expert, in an Earth Observatory post. "Pingualuit Crater Lake is always the last to freeze in the winter and the last to melt in the spring."
Bowl City Crater
Discovering a crater
Image captured by NASA's Landsat 7 satellite on Aug. 17, 2002.