Amchitka: Its Geophysics and Hydrogeology

University of Alberta
Student Contributor


Nature is doing a great job of tearing apart the Alaskan island of Amchitka. But humans have made matters worse. Three underground nuclear tests have contiminated the island, and someday a lethal Cold War cocktail may well leach into the Pacific.

Editor’s Note: Nils Peterson is this year’s University of Alberta geoscience student contributor to The PEGG. The fourth-year student of the geology program will graduate this year with honours. “In addition to studying rocks,” he says, “I like climbing on and hiking over them.”

The Cold War was a time of international tension, unprecedented militarization, and, unfortunately, a lot of nuclear testing. While many have seen pictures of mushroom clouds rising above the Nevada desert, or the obliteration of a small island in the Pacific, few know of the three bombs that were detonated under a small Aleutian island called Amchitka, off the west coast of Alaska.

Stark, Beautiful – Deadly?
Amchitka’s beauty is hard to ignore. And so is its human stain, the result of Cold War nuclear testing.

It is on this island, the site of the largest underground nuclear test in history, that William Shulba, a U of A geology student, spent 10 days of his summer.

Before the Second World War, Amchitka was one island in a wildlife refuge, but during the war its strategic location, close to the USSR, made it a perfect base for military operations. After the war the military and conservationists vied for control of the island, but eventually it was chosen as a site for underground nuclear tests.

In 1971, a whopping five-megaton nuclear bomb, Cannikin, was detonated 1,800 metres below Amchitka. The blast remains the largest underground explosion ever. It registered 7.1 on the Richter scale, in fact, and produced a crater almost two kilometres wide, which has since become the island’s biggest lake.

One of the scientists on the island at the time of the test said the surrounding ocean water turned to foam. Though most don’t remember it now, it was also the event that spurred the creation of Greenpeace.

Not a Good Test Site
It was later found that Amchitka is about the worst possible place to detonate a nuclear weapon, revealing a frightening lack of foresight. The island is not a stable chunk of rock that won’t leak radiation for thousands of years; rather, it is an island that is being stretched apart at a geologically fantastic rate.

The Aleutian chain of islands is volcanic, and owes its existence to the subduction of the Pacific tectonic plate beneath the North American plate, a process that is tearing Amchitka apart.

In the 1960s plate tectonics was still seen as a deeply flawed theory by many scientists, and no one knew the full impact that oceanic plates play in the slow waltz of the Earth’s crust. The concern over radiation leakage in the fresh water beneath the island is what brought a geophysical research team to Amchitka this summer.

“It is interesting to see that the human footprint can extend to the furthest reaches of our planet. It was quite disappointing to see the state in which the islands [Amchitka and neighbouring Adak] were left in after war times,” says William Shulba, who spent the summer months doing geophysical research with U of A professor Martyn Unsworth.
“On the surface the islands demonstrate such beauty and grace, but they have been defiled by military operations. It is reassuring to know that there is a community willing to scientifically characterize these problems.”

The surface of the island was cleaned up in 2001 but a sub-surface survey hasn’t been done since the ’70s, and thanks to plate tectonics, the island is continuing to stretch and fracture. The research team used geophysical methods to characterize how the island is fractured, and thus determine how quickly radioactively contaminated fresh water beneath the island is likely to leak into the ocean.

When Will it Seep?
With a population of Aleut natives as well as local fishermen, it is important to know when contaminated fresh water starts seeping into the Pacific; it may happen in the next 100 years, though fortunately it hasn’t happened yet. Thanks to the efforts of researchers, government and the community, there should be ample warning when Amchitka finally gives up.

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