Green Lake, and Scolopendrium Pond. The botanist R. C. Benedict wrote in 1915, "the lake itself is of equal geological interest and, from the standpoint of the hart's tongue fern, is of greater interest than the west lake region because the best specimens in the country grow near the east lake." This lake was threatened by limestone quarrying in 1915 when Benedict wrote his letter to Science, and Benedict had been seeking support for the creation of another state park to protect Green Pond. Clark Reservation had recently been preserved from the same threat. By 1925 the threat to the eastern lake had become reality, and this lake was destroyed by expanded limestone quarrying. Just prior to its destruction, about 1000 hart's tongue ferns were transplanted from its vicinity to Clark Reservation. One author has claimed that the conversion of Clark Reservation into a state park in 1926 occurred because of interest in preserving the American hart's tongue fern. In 1930, a state law was passed protecting hart's tongue fern in Onondaga County and also neighboring Madison County; nonetheless, destruction of habitat in the nearby Rock-cut gorge had destroyed still another station of these ferns by 1945. Geology The fossil waterfall and many of the topographical features of Clark Reservation were created about 10,000 years ago, near the end of the most recent ice age (the Wisconsin glaciation). A few miles west of Clark Reservation, glacial Lake Cardiff occupied the deep, Onondaga trough. Just east of Clark Reservation lay a similar glacial lake occupying the Butternut trough. Both troughs run north-south, aligned with the advance and retreat of the ice sheets that have scoured New York. The retreating ice sheet blocked the northern ends of both glacial lakes, so as Cecil Roseberry describes, "The southern environs are furrowed with rock channels slashed by torrents of glacial meltwater seeking an escape route which they finally found to the Mohawk Valley." These rock channels are now called "the Syracuse channels". Because the elevation of the land in this region generally decreases from south to north, a series of channels was created by the northerly retreat of the ice sheet; each succeeding channel is lower, and more northerly, than the previous one. Smoky Hollow, which is a gorge lying about a mile south of Clark Reservation, was an early channel created by flows of water from Lake Cardiff into the Butternut trough when