The Niagara Escarpment is a bedrock cliff that arcs for almost 1,000 miles from southeastern Wisconsin through northern Michigan and Ontario to central New York. On the Green Bay side of the Door Peninsula, the escarpment rises in steep cliffs up to 250 feet high. The Door Peninsula is a cuesta, a ridge of tilted bedrock created from sediments deposited in a vast inland sea over 400 million years ago. The Niagara Escarpment forms the steep cliff face of this tilted bedrock along Green Bay, while the bedrock angles down across the peninsula to a Lake Michigan shoreline with low cliffs. Niagara Falls in New York plunges over the same rock formation.