Mudboil

Mudboils are muddy springs composed of water, fine sand and silt, and dissolved salt chiefly found in the Tully Valley in Onondaga County, in central New York State, although they have also been observed for shorter periods of time following earthquakes in Alaska and California. They range from several inches to more than 30 feet in diameter, and ebb and flow dynamically: some will discharge large amounts of sediment over several days and then stop flowing, while others will flow continuously for multiple years. The phenomenon has been observed since the late 1890s.

The Tully Valley mudboils are associated with a history of brine extraction in the area, which began in the late 1880s. The halite beds in the Tully Valley lie under a 400-foot layer of glacial sediments and a 1000-foot layer of shale and limestone that separated them from the aquifer until salt extraction began. Brining has also caused ground subsidence in the areas above the salt beds.

Tons of sediment, as well as dissolved salt, are deposited by the mudboils into Onondaga Creek on a daily basis. Members of the Onondaga Nation report that as recently as the 1940s, the now-turbid water was clear and that tribe members used to swim and fish in the river.