Raising awareness among local residents about risks is a challenging task. On a cloudy September day, Heidi Giegel is negotiating the known roads on an unpaved path in Seldovia, Alaska. When she reaches the top of a hill adorned with a small church, her town spreads below her – in the bay, fishing boats sway gently; on the shore, there’s the Linwood Bar & Grill and Crab Pot grocery store, along with dozens of houses on stilts.
Alaska Tsunamis
Alaska is prone to two types of tsunamis. Tectonic tsunamis, which are associated with the long chain of volcanic islands that stretch like a tail from the southern part of the state; those islands represent the northern edge of the Ring of Fire, a geologically active area that generates about 90 percent of the world’s earthquakes. Tracking those islands is the underwater Alaska-Aleutian trench, where massive plates of solid rock interact and friction accumulates slowly. Once or twice a year, the subduction zone generates earthquakes strong enough to trigger tsunami warnings; every 300 to 600 years or so, it erupts in a giant earthquake that sends devastating tectonic tsunamis crashing onto Alaska’s shores.
Collapse Tsunamis
Alaska’s sprawling 34,000-mile wilderness coastline also makes a second type of tsunami possible: collapse tsunamis. The southern coast of Alaska is dotted with active volcanoes and hundreds of fjords surrounded by unstable cliffs, with a thick layer of clay sediments below in the deep water. Relatively small earthquakes, common in Alaska, shake this unstable environment, causing landslides above and below sea level that displace massive amounts of water. The resulting tsunamis can reach coastal communities within minutes. With the accelerating melting of glaciers and subsequent erosion in these areas due to climate change, these collapse-generated tsunamis are becoming more likely.
Preparing for Tsunamis
Planning for tsunamis is difficult. Tsunami science is still in its early stages, having only emerged due to the advent of computer modeling in the 1980s. Scientists in Alaska lack the technology needed to predict tsunamis before they occur in the state since they happen very quickly. For many Alaska residents, the last major tsunami event in 1964 is a distant memory. False alarms cause evacuations at least once a year, leading people to question why they should leave when no waves are visible. These challenges are complicated by a culture that may be wary of outside experts. “I know the history,” says Elena Sleimani, a tsunami simulator on the government team working at the Alaska Earthquake Center at the University of Alaska Fairbanks. “I know every single detail about what happened in 1964. And the people who live there, they don’t know that.”
Future Challenges
As community leaders and scientists prepare for the next big wave, they face a constant question: How can they convince people that they are at risk from a disaster that is unpredictable, spans several generations, and is guaranteed to be catastrophic when it occurs?
On March 27, 1964, the second largest earthquake in recorded history, measuring 9.2 in magnitude, struck off the southern coast of Alaska. Streets in Anchorage cracked open, and an entire neighborhood fell into the sea. Within minutes, underwater landslides along parts of the shoreline triggered local tsunamis. Then the tectonic tsunami hit, inundating communities repeatedly for hours. More than 20 tsunamis struck Alaska, resulting in the deaths of 106 people statewide and causing $284 million in damages. In Seldovia, the ground shook for nearly three minutes and then sank permanently by 3.5 feet. The highest wave of the tectonic tsunami that reached the town, measuring 26 feet, was not significant in itself, as it arrived at a low tide. But during the next high tide, the town was submerged underwater and had to be rebuilt.
Remember
Darlin Crawford, a village chief of Seldovia, felt as if she endured the shaking of her home forever before leading her four small children to a high hill on that cold night. She says the effects of the Good Friday earthquake still linger today – the urban renewal project to demolish the town split the community, and only one factory returned, drastically altering the commercial crab fishing economy. “It has drastically changed Seldovia’s life,” she said. “The town was empty for a long time.”
However, Seldovia faced a better fate than most towns, partly due to its sheltered location in Kachemak Bay. On the opposite side of the Kenai Peninsula, communities like Seward, where Crawford’s parents lived, did not fare so well. There, waterfront warehouses and fuel storage tanks slipped into Resurrection Bay, then returned to shore within minutes from waves roaring over 30 feet. The original village of Chenega, an Indigenous community in Alaska near Seward, lost a third of its population and was never relocated. Its residents were initially dispersed throughout Alaska before rebuilding a new community on a nearby island.
Next time, Seldovia may not be so lucky. Tsunamis are as unpredictable as they are unavoidable. And if the next massive earthquake strikes at high tide, the waves could wipe Seldovia off the map.
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