Peninsula State Park is shaped by rock and water, with rocky bluffs rising more than 150 feet as part of the 650-mile Niagara Escarpment, a fossil-rich sedimentary formation that began to form 420 million years ago along the outer rim of a shallow sea. Today this escarpment forms the backbone of the park, and its varied terrain provides critical habitat for 500-year-old cedar trees, delicate ferns, and rare land snails. The park also has eight miles of shoreline that is continually changed by waves and ice, leaving rounded cobbles and boulders near the water's edge. Brachiopod and coral fossils from the ancient Silurian Sea may be embedded in the rock, and brachiopods, two-shelled ocean animals, lived here millions of years ago. Cedar trees survive on the cliffs by rooting into rock crevices that hold small amounts of soil and moisture, aided by algae and fungi, and at least a few of these ledge-loving cedars are more than 500 years old.