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The third dacite lava dome began to appear on October 18, 1980 above the lip of a 25-metre-diameter feeding conduit. Helens' new lava dome is composed of 74 million cubic meters of dacite flows and intrusions built up within the crater between October 18, 1980, and October 26, 1986 The view is toward the north looking over the lava dome into the 1980 blast zone (photo by Lyn Topinka of the US Geological Survey, after Pringle, Ref. After October 18, 1980, this third and newest composite dome of dacite began to appear.