Kasatochi Island has a unique landscape that makes it an ideal home for many types of species. Some of these aspects that created such a beneficial habitat reflected strictly on the island's geology. Before 2008, the island was about 3 km in diameter and stood about 314 m high on the highest side. The island is steeper to the northern side than the southern side, and slightly north of the center of the island is a steep-walled caldera surrounding a lake. The crater is about 4,000 feet in diameter, with its lake's surface lying only about 60 m above sea level. In all areas surrounding the crater, the island is characterized by steep sea-cliffs, talus slopes, and small, boulder-filled beaches. These many habitat possibilities set the stage for the numerous species that took residence there.