Aniakchak National Monument and Preserve
 Remote and Recent Volcanic Wildlands
Midway down the wild and roadless Alaska Peninsula in the Ring of Fire lies one of the Nation’s most fascinating recent volcanic features.
Aniakchak, part of the US National Parks, 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. Then,
geographers remotely plotting mountain locations along the caldera’s rim notice their circular configuration. Eventually, in 1922, a geologic
field party gazed down into the caldera. They brought back news of Aniakchak’s immense proportions.
Calderas
 Although a dozen calderas stand on the Alaska Peninsula, Aniakchak ranks among the largest. Its fascinating volcanic history can
be read from its exposed internal plumbing. 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. Because some explosion
features seem to have been created underwater, the caldera probably once contained a deep snow-fed lake, much like Crater Lake in southern
Oregon. Eventually, however, at a low place along the rim, lake waters began to spill out. Over time, this fast-flowing stream created the
great breach in the rim known as The Gates. The Gates now allow the Aniakchak River to begin its tumultuous 27-mile course southeastward to
the Pacific Ocean.
 Father Bernard Hubbard in the US National Parks
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.
Alaska Ring of Fire
Aniakchak is part of the Ring of Fire. In this active volcanic area along the Pacific Ocean rim, volcanoes occur as the Pacific plate is
thrust, or subducted, beneath continental plates. Very explosive, these subduction volcanoes produce large volumes of ash. They build island arcs
and high mountain chains. Aniakchak is cousin to America’s Katmai, Redoubt, and Mt. St. Helens and to Japan’s Fuji and Indonesia’s Krakatau.
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