Volcanic crater lake

The water may come from precipitation, groundwater circulation (often hydrothermal fluids in the case of volcanic craters) or melted ice.

Sources of water loss singly or together may include evaporation, subsurface seepage, and, in places, surface leakage or overflow when the lake level reaches the lowest point on its rim.

At such a saddle location, the upper portion of the lake is contained only by its adjacent natural volcanic dam; continued leakage through or surface outflow across the dam can erode its included material, thus lowering lake level until a new equilibrium of water flow, erosion, and rock resistance is established.

If the volcanic dam portion erodes rapidly or fails catastrophically, the occurrence produces a breakout or outburst flood.

[7] Certain bodies of water, although their formation is directly related to volcanic activity, are not usually referred to as crater lakes, including: