Nunivak Island - Geology and Natural History

Geology and Natural History

Nunivak Island is volcanic in origin; most of the island is dominated by volcanic plateau 500 ft (160 m) or more above sea level. The island is dotted with about 60 cinder cones and four maars. Much of its surface consists of widespread, thin flows of pahoehoe lava from small shield volcanoes, which spread over sedimentary rock of the Cretaceous period. Volcanic eruptions took place during 5 periods of activity beginning 6.1 million years ago. Most of the volcanic field was formed during two eruptive periods during the Pleistocene ending about 300,000 years ago, but volcanic activity continued into the Holocene.

Tundra is the main landscape feature; the largest trees on Nunivak are dwarf willow trees, most less than 4 ft (1.2 m) tall. More than 40 rivers drain the tundra upland. Brackish lagoons ring the eastern and southern shores, and steep volcanic cliffs dominate the northwest shores.

At least 89 migratory seabird and waterfowl species have seasonal homes on Nunivak Island, including several endangered and threatened species. Dense summer breeding rookeries are found on all shores of the island and in inland tundra lakes.

Prehistorically, Nunivak was home to a modest herd of caribou, but these were exterminated after the introduction of firearms in the late 19th or early 20th century. United States Fish and Wildlife introduced reindeer and musk ox onto the island in the 1930s and 1940s. Large herds of these animals are maintained by the local Native Corporation of Mekoryuk.

Most of the island is part of the Yukon Delta National Wildlife Refuge, administered by the U.S. Fish and Wildlife Service.