Flowing water eroded away until this durable limestone strata. The majority of sedimentary rock is shale, only 6% is limestone. Throughout the Finger Lakes and elsewhere, this is why when flowing water exposed the edge of a limestone strata, the underlying, soft shales are worn away to reveal a waterfall, ever deepening. Eventually, the support of the limestone washes away to form this ledge. Here it is an ephemeral cave behind a curtain of ice.
See “The Fang?” for the first post of this series.