Molokaʻi developed from two distinct shield volcanoes known as East Molokaʻi and the much smaller West Molokaʻi. The highest point is Kamakou on East Molokaʻi, at . Today, East Molokaʻi volcano, like the Koʻolau Range on Oʻahu, is what remains of the southern half of the original mountain. The northern half suffered a catastrophic collapse about 1.5 million years ago and now lies as a debris field scattered northward across the bottom of the Pacific Ocean. What remains of the volcano on the island include the highest sea cliffs in the world. The south shore of Molokaʻi boasts the longest fringing reef in the U.S. and its holdings—nearly long.