Layers of sand and mud accumulated and eventually turned to stone, under the enormous weight of sediments over millions of years. When conditions were just right, fossils of sea animals were sometimes preserved. Fossils, however, are not common in the glen. The entire region is criss-crossed by joints. They formed violently millions of years ago when mountain building forces to the southeast raised western New York as a plateau.
Joints often become sites for erosion.
Floods can pry out slabs along joints. Quarries often take advantage of natural jointing. Look for joints elsewhere in the gorge. Past Glory - The large concrete footings here look like stepping stones for a giant to cross the glen. They once supported a high railroad trestle which brought thousands of tourists to Stony Brook.