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King Salmon, Alaska
Midway down the wild and roadless Alaska Peninsula lies one of the Nation's most fascinating recent volcanic features. Aniakchak is a 6-mile-wide, 2,000-foot-deep caldera formed by the collapse of a 7,000-foot mountain. Lying inland in a region of frequent clouds and stormy weather, Aniakchak remained unknown to all but native inhabitants until the 1920s.
The Aniakchak Caldera, is the result of a series of eruptions, the latest in 1931. Nearly six miles in diameter and covering some ten square miles, it is one of the finest examples of dry caldera in the world. Located in the volcanically active Aleutian Mountains, the crater contains many outstanding examples of volcanic features, including lava flows, cinder cones, and explosion pits. Surprise Lake, located within the caldera, is the source of the Aniakchak River, which cascades through a 1,500-foot gash in the caldera wall. The site also contains the Aniakchak Wild River.
About 3,500 years ago, a dramatic explosion caused the loss of some 3,000 feet of the upper mountain. The remainder of the mountain next collapsed, leaving a relatively flat-floored, ash-filled bowl. Since the caldera first formed, many lesser eruptions have created the small cinder cones, lava flows, and explosion pits dotting its floor today. Wave-carved terraces high on the caldera wall indicate that the caldera once contained a deep snow-fed lake, much like Crater Lake in Southern Oregon. However, hydraulic pressure or overflow eventually led to a breech of the caldera wall at a weak or low point. The result was a massive flood that created the great cleft through the caldera wall now known as The Gates. The Gates now allows the Aniakchak River to begin its tumultuous 27-mile course southeastward to the Pacific Ocean.
Aniakchak's most recent volcanic activity came in 1931. A small but impressive explosion pit was added to the pockmarked caldera floor that year. Many thousands of tons of ash lay strewn within the caldera and scattered up to 40 miles away over the small villages. Fortunately, this volcanic episode was documented both before and after by an indomitable geologist and Jesuit priest, Father Bernard Hubbard. His photographs and descriptions provide an important benchmark for judging the likely rate of recovery of vegetation to the devastated caldera. Mosses, grasses, and more complex flowering plants have invaded sheltered spots. Brown bear and caribou have returned. Spawning runs of sockeye salmon now fight their way up the Aniakchak River and into Surprise Lake, the river's shallow headwater lake inside the caldera.
In creating Aniakchak National Monument and Preserve, Congress recognized the unique geological significance of the caldera and also acknowledged the outstanding wildlife and recreational values of the Aniakchak River by designating it a wild river within the National Wild and Scenic Rivers System. The parklands boundaries also contain other important resources. West of the caldera lies the waterfowl and migratory bird habitat of Bristol Bay's coastal plain. To the east, rugged bays and inlets of the Pacific coast and offshore islands provide habitat for sea mammals and sea birds. Evidence of ancient human presence at Aniakchak is minimal. However, more may one day be known of this important transition zone between ancestral Aleuts and Yupik-speaking people.
Operating Hours & Seasons
There are no federal facilities at the Monument.
Getting There
Access to the park is by plane or float plane from King Salmon, Alaska or by power boat from any one of the numerous villages along the Pacific Ocean coastline.
Getting Around
There are a no formal trails within the monument/preserve although open ash fields provide hiking/backpacking opportunities.
Return to Alaska National Parks Index
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