Since the early 20th century, nearly all of Earth’s glaciers have been retreating or melting. Glaciers cover 10 percent of the planet’s land area and contain 75 percent of our fresh water. Moreover, the water from melting glaciers accounts for nearly two-thirds of the observed rise in global sea levels. Despite the looming ecological consequences, glacier motion remains poorly understood because of a lack of research on how large ice masses sheer and flow in contact with bedrock.