page_title: Lake Clark National Park and Preserve
section_title: Geology
hierarchical_section_title: Lake Clark National Park and Preserve / Geology
caption_attribution_description: English: Lake Clark geologic map. Jtk is the Jurassic Talkeetna Formation, Jqd is Jurassic quartz diorite, tonalite and diorite, Kgd is Cretaceous granodiorite, Tmv are Tertiary (Oligocene and Eocene) volcanic rocks, Tigd is Tertiary (Paleocene) granodiorite
context_page_description: Lake Clark National Park and Preserve is an American national park in southwest Alaska, about 100 miles southwest of Anchorage. The park was first proclaimed a national monument in 1978, then established as a national park and preserve in 1980 by the Alaska National Interest Lands Conservation Act. The park includes many streams and lakes vital to the Bristol Bay salmon fishery, including its namesake Lake Clark. A wide variety of recreational activities may be pursued in the park and preserve year-round. The park protects rainforests along the coastline of Cook Inlet, alpine tundra, glaciers, glacial lakes, major salmon-bearing rivers, and two volcanoes, Mount Redoubt and Mount Iliamna. Mount Redoubt is active, erupting in 1989 and 2009. The wide variety of ecosystems in the park mean that virtually all major Alaskan animals, terrestrial and marine, may be seen in and around the park. Salmon, particularly sockeye salmon, play a major role in the ecosystem and the local economy. The Kvichak River is the world's most productive watershed for sockeye salmon.
  Large populations of brown bears are attracted to feed on the spawning salmon in the Kijik River and at Silver Salmon Creek.
context_section_description: The park has four main physiographic regions. The upthrust granite Chigmit Mountains connect the Alaska Range to the Aleutian Range. Superimposed on these mountains and  little to the east of the main range are the two stratovolcanoes, Redoubt 10,197 feet (3,108 m) high, and Iliamna at 10,016 feet (3,053 m). Glaciers have altered the mountains, carving cirques and U-shaped valleys into the range, which end abruptly on the east at the steep coast in deep bays or in outwash flats. On the west the glaciers have cut deeply enough to create lakes, dammed by terminal moraines at their downstream ends. Lake Clark, the largest, is the sixth largest lake in Alaska, 860 feet (260 m) deep and 42 miles (68 km) long.
  The park includes a variety of unrelated rocks. The core of the Chigmit Mountains is a granite pluton forced upwards  by the collision of the Pacific plate and the North American plate. Rocks in coastal areas are sedimentary in origin, and contain abundant fossils. Volcanic rocks intrude through these native rocks.
caption: Lake Clark National Park geologic map
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