Plunge pool Plunge pool A plunge pool (or plunge basin or waterfall lake) is a deep depression in a stream bed at the base of a waterfall or shut-in. It is created by the erosional forces of cascading water on the rocks at formation's base where the water impacts. The term may refer to the water occupying the depression, or the depression itself. Plunge pools are formed by the natural force of falling water, such as at a waterfall or cascade; they also result from man-made structures such as some spillway designs. Plunge pools are often very deep, generally related to the
Marsh funnel Marsh funnel The Marsh funnel is a simple device for measuring viscosity by observing the time it takes a known volume of liquid to flow from a cone through a short tube. It is standardized for use by mud engineers to check the quality of drilling mud. Other cones with different geometries and orifice arrangements are called "flow cones", but have the same operating principle. In use, the funnel is held vertically with the end of the tube closed by a finger. The liquid to be measured is poured through the mesh to remove any particles which might block the