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 time of 100 or more seconds. While the most common use is for drilling muds, which are non-Newtonian fluids, the Marsh funnel is not a rheometer, because it only provides one measurement under one flow condition. However the effective viscosity can be determined from following simple formula. μ = ρ (t - 25) where μ = effective viscosity in centipoise ρ = density in g/cm³t = quart funnel time in seconds For example, a mud of funnel time 40 seconds and density 1.1 g/cm³ has an effective viscosity of about 16.5 cP. For the range of times of typical muds