When waves that would otherwise break on an open shore are instead forced underneath an apron of shore-fast ice, the surge may spout violently through small holes in that ice. If it’s cold enough, the water, falling back, will splatter and freeze around the opening. If the air is calm and the spout is strong and sufﬁciently high, the freezing water will build up around the spout hole in the shape of a cone, sometimes to the height of ﬁve feet or more. The process compares with the way spatter cones are created around fumaroles, the vents on active volcanoes. Ice volcanoes continue to grow until the surge subsides or the vent freezes shut. They sometimes occur in clusters, as is commonly the case along the winter shores of Lake Superior.