By Liz O'Connell for Frontier Scientists
“By dating ash,” said Richard Vanderhoek, “an archaeological site in Alaska, can be placed on a chronostratographic timeline.” Or in other words: the chemical makeup of the ash, matched with a volcano eruption, will provide an approximate date of the site. Archaeologists worldwide have dated ancient sites for the last half century in this manner.
Vanderhoek wants to consider not just the timing of the catastrophic event, but the ecological and cultural impacts on the environment and people. Once a region has been devastated by fire, ash, pyroclastic flows (lava), or a lahar—a river of mud and volcanic debris; the region takes a long time to rejuvenate. The vegetation is slow to grow back. People oftentimes leave the area and their home sites immediately. Those home sites decades later are found with many house and tool remnants intact.
Three major volcanic eruptions impacted people living in the Far North during the last 12,000 years.
- Aniakchak, on the Katmai Peninsula
- Mt Hayes vent, west of Anchorage
- White River, in the Wrangle Mountains
Aniakchak first erupted over 3,500 years ago. In historic times, the ash from the May 1931 eruption of Aniakchak fell at a rate of a pound per hour at the Chignik villages, 65 miles to the south. The blast was heard 200 miles away and the ash sprinkled the ground nearly 700 miles from the source. The eruption left a caldera 250 deep and one-half mile wide. (see photo)
Hayes Volcano was not discovered until 1975. It is responsible for a series of six major tephra layers in the Cook Inlet region of Alaska. Hayes was mostly destroyed by at least six catastrophic eruptions between 3,400 and 3,800 years ago, and the average volume of these eruptions was 2.4 cubic km. In comparison, the volume of the May 18, 1980 eruption of Mount St. Helens was about 1 cubic km. There is currently no fumarolic activity present. The last eruption of Hayes Volcano occurred roughly 1,200 years ago.
White River ash is the product of two of the most voluminous pyroclastic eruptions in North America in the past 2,000 years, blanketing much of the Yukon Territory, Canada, and a small part of adjoining eastern Alaska. Mount Churchill has been identified as the source of the White River Ash. The total volume of the ash exceeds 12 mi³ (50 km³), or roughly 50 times the volume of the 1980 eruption of Mount St. Helens, and ash layers up to 2 ft (60 cm) thick can be seen just below the surface in many roadcuts along the Alaska Highway.
Yet these Alaskan volcanoes did not make the top ten volcanic eruptions list created by the Science Discovery Channel. The Discovery Channel list includes: 1.) Tambora, Indonesia-1815, 2.) Krakatoa, Indonesia-1835, 3) Mr. Pelee, Martinique-1902, 4) Vesuvius, Italy-79, 5) Kilauea, United States-1983, 6.) Nevada del Ruiz, Colombia-1985, 7.) Mount St. Helens, U.S.-1980, 8) Mt. Pinatubo, Philippines-1991, 9) El Chichon, Mexico-1982, 10) Unzen, Japan-1972. It is unclear what criteria Discovery Channel use to elevate an eruption to the list, but Alaska’s volcanoes have spewed more ash than some on the list.
Alaska, situated on the 'Ring of Fire,' an area circling the Pacific Ocean basin, is where a large number of earthquakes and eruptions occur. The entire Ring of Fire has 452 active volcanoes and is home to 75% of the world’s active and dormant volcanoes. The Alaska volcanoes located on the Aleutian volcanic arc alone contain 44 of the 54 active volcanoes in the U.S.
Arctic Volcanism is one topic at the 40th Annual Meeting of the Alaska Anthropological Association March 13-16 in Anchorage at the Hotel Captain Cook. Hosted by the Bureau of Indian Affairs and the Smithsonian Arctic Studies Center, the Conference Theme “Back to the Source” seeks to highlight new collaborations across the North in oral history, archaeology, cultural studies, linguistics, human biology and museums. The Agenda for the meeting is located at www.AlaskaAnthropology.org.