A
volcanic dam is a type of
natural dam produced directly or indirectly by
volcanism, which holds or temporarily restricts the flow of surface water in existing streams, like a man-made
dam. There are two main types of volcanic dams, those created by the flow of molten
lava, and those created by the primary or secondary deposition of
pyroclastic material and debris. This classification generally excludes other, often larger and longer lived dam-type geologic features, separately termed
crater lakes, although these volcanic centers may be associated with the source of material for volcanic dams, and the lowest portion of its confining rim may be considered as such a dam, especially if the lake level within the crater is relatively high.