An icefall is a portion of certain glaciers characterized by rapid flow and a chaotic crevassed surface. The term icefall is formed by analogy with the word waterfall, a similar, but much higher speed, phenomenon. When ice movement is faster than elsewhere, because the glacier bed steepens or narrows, the flow cannot be accommodated by plastic deformation and the ice fractures, forming crevasses. Where two fractures meet, seracs (ice towers) can be formed. When the movement of the ice slows down, the crevasses can coalesce, resulting in the surface of the glacier becoming smoother

https://en.wikipedia.org/wiki/Icefall

East lobe of the Tulutson Glacier on Mount Saint Helens

By John Pallister (USGS) - http://vulcan.wr.usgs.gov/Volcanoes/MSH/Images/MSH04/crater_dome_eruption_october_2006.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1594282