OnDemand - 250K - HYDRO - Underground Conduit - Line

A set of naturally occurring subsurface drainage channels formed from the dissolution of soluble rocks in Karst terrain or in terrain similar to karst but formed in nonsoluble rocks, as by melting of permafrost or ground ice, collapse after mining, and by outflow of liquid lava from beneath its solidified crust. The accuracy within which the feature may be confidently positioned is unknown.