A “bizarre”-looking vortex has opened up in Lake Berryessa, located in California's Napa Valley, according to the Daily Express.
This is not exactly an uncommon occurrence, as this phenomenon occurs when the waters in the lake rise too high and 22-meters wide spillway comes into play, the media outlet notes.
The spillway helps drain the excess water from the reservoir, which was formed after the construction of the Monticello Dam in the 1950s, and creates a sight that the locals refer to as the “Glory Hole”.
As ScienceAlert points out, the concrete structure that serves as the spillway is called a bell-mouth, and similar structures have been used to “control the water level of several other dams around the world”, though the one located at Lake Berryessa is probably one of the more famous.
While the reservoir is currently roped off, with swimming and boating being prohibited there, in 1997 a woman named Emily Schwalek ended up dying after being caught in the current and swept down the pipe, hers being the only recorded human death associated with the pipe.
While the spillway’s architects in the 1950s thought that their creation would be used only once every 50 years, the “Glory Hole” has opened up three times since the beginning of this century, ScienceAlert adds.