Within the park the mountains of the Alaska and the Aleutian ranges meet. The Chigmits, an awesome, jagged array of mountains, are the result of centuries of uplifting, intrusion, earthquakes, volcanism, and glacial action. The two active volcanoes of Iliamna and Redoubt, form an important link to the Pacific Ring of Fire. Venting steam, snowcapped, and rising more than 10,000 feet, each is an impressive volcano to be viewed from the eastern side of the park. The range's eastern flank descends rapidly to Cook Inlet.
Rivers cascade dramatically to the sea through forests of Sitka and white spruce.
Coastal cliffs comprised of fossil remnants millions of years old are stark counterpoints to the active volcanoes and glacial streams that are currently reshaping the landscape. On marshes and outwash plains, swans and other waterfowl nest. The rocky cliffs provide rookeries for puffins, cormorants, kittiwakes, and other seabirds. Seals and whales may occasionally be observed offshore. The western flank of the Chigmit Mountains descend through tundra covered foothills to boreal forest.