Icy Flows

The surface of Mars is littered with examples of glacier-like landforms. While surface ice deposits are mostly limited to the polar caps, patterns of slow, viscous flow abound in many non-polar regions of Mars. Streamlines that appear as linear ridges in the surface soils and rocky debris are often exposed on top of infilling deposits that coat crater and valley floors. We see such patterns on the surfaces of Earth's icy glaciers and debris-covered "rock glaciers." As ice flows downhill, rock and soil are plucked from the surrounding landscape and ferried along the flowing ice surface and within the icy subsurface. While this process is gradual, taking perhaps thousands of years or longer, it creates a network of linear patterns that reveal the history of ice flow. Later and under warmer conditions, the ice may be lost through melting or sublimation. (Sublimation is the evaporation of ice directly from solid to gas without the presence of liquid.) Rock and minerals concentrated in these long ridges are then left behind, draped over the preexisting landscape. https://photojournal.jpl.nasa.gov/catalog/PIA25984