The fumaroles on Lastarria have created widespread deposits of sulfur. The sulfur has also formed flows, of which the two largest are and long. The longer flow is partly buried by the shorter one and has already lost part of its surface structure. No vents have been found; sulfur flows appear to emerge from the fumarolic terrain. One andesite lava flow has generated several subsidiary sulfur flows that resemble pahoehoe flows and have widths of . It is likely that sulfur deposited by fumaroles formed such flows. Some fumaroles currently release centimetre-long sulfur flows. Flows of sulfur are highly fragile constructs that can easily be destroyed.