Tag Archives: tsunami

Alaska Jökulhlaup

A large glacial dam gave way in Southeast Alaska this summer. Known by its Icelandic term: jökulhlaup, the power of this sudden release of pent up water can be incredibly destructive.

The terminus of Lituya Glacier; Photo credit: NPS/J. Capra

Desolation Lake, which sits above the Lituya Glacier in Desolation Valley, collects meltwater from both the Desolation and Fairweather Glaciers. That meltwater is normally blocked by the Lituya Glacier, forming the roughly four square mile lake.

The water level suddenly dropped 200 feet.

A commercial fisherman, Jim Moore, along with his two grandsons, tried to enter Lituya Bay to fish for Chinooks in August. They should have been riding the tide into the bay, but the unusually muddy water was moving outward, and it was filled with trees and other debris. The bay was also filled with small icebergs. Moore managed to bring some of the ancient ice onboard for his coolers, then left the bay, instead of fighting the dangerous current.

Lituya Glacier terminus and delta; Satellite image credit: USGS

It is one of the largest jökulhlaups known to have occurred in Alaska. The water found a path under the Lituya Glacier, causing a rush that would have rivaled the hourly discharge of the Amazon River. It would have lasted for several days.*

Lituya Bay has a history. In 1958, an earthquake triggered a landslide that started one of the largest known tsunamis at over 1700 feet.

*NPS Geologist, Michael Loso


Scotch Cap Lighthouse

Scotch Cap Lighthouse 1903
The Scotch Cap Light in 1903.

The Scotch Cap Light was the first lighthouse on the outer coast of Alaska. It was built on Unimak Island in the Aleutian Chain in 1903.

Scotch Cap Lighthouse
Scotch Cap Light in 1940

In 1940, a new Scotch Cap Light was built out of reenforced concrete and a fog signal was added. From the beginning, the lighthouse was the scene of several shipwrecks, including the Columbia in 1909, which forced the crew of 194 to spend two weeks on Unimak as guests of the lighthouse keepers until they could be rescued. And in 1930, a Japanese freighter became lost in a snowstorm and beached in front of the light.

The 1946 Aleutian Islands Earthquake hit the chain of islands on April 1 of 1946. The 8.1 magnitude quake generated a Pacific wide tsunami. The massive wave wiped Scotch Cap Light right off the face of Unimak Island. Anthony Petit, the lighthouse keeper, and his five man crew were killed by the wave that is estimated to have been at 130 feet high.

Unimak Island 1946
Unimak Island after the 1946 tsunami.

The tsunami that resulted from the Aleutian Earthquake killed 165 people: 159 in Hawaii and six in Alaska. It took the tsunami 4.5 hours after the quake to hit Kauai and 4.9 to strike Hilo, causing over $26 million in damage. After the destructive tsunami, the Seismic Sea Wave Warning System was established in 1949, eventually becoming the Pacific Tsunami Warning Center.

Hilo 1946 Tsunami
Residents of Hilo, Hawaii fleeing the 1946 tsunami.

Photos of Unimak and Scotch Cap courtesy of USCG. Hawaii photo courtesy of NOAA


The Good Friday Earthquake

64 Quake Map

It was 50 years ago today, at 5:36pm AST, when the megathrust earthquake hit southern Alaska. The ground shook for over 4 minutes, causing tsunamis that wiped out coastal villages before the shaking stopped. The magnitude 9.2 quake remains the largest to be recorded in North America. In the five decades since, no earthquake has matched the power of the 1964 Good Friday Earthquake.

Kodiak, AK after Good Friday Quake
Kodiak after the 1964 Alaska Quake. Note the green Willys Wagon!

139 lives were lost (tsunami 124, earthquake 15), which, considering the magnitude of the quake, is amazingly low. The maximum tsunami wave height recorded was 67 meters (220 feet) at Shoup Bay in the Valdez Inlet. The community of Valdez was wiped out. Kodiak, Seward, Portage, Anchorage, Chitina, Glenallen, Hope, Homer, Moose Pass, among others, all saw severe damage.

4th Ave Anchorage B&W
4Th Avenue, Anchorage after the ’64 Quake

In the day following the earthquake, there were 11 major aftershocks that reached a magnitude of 6.2 or higher. There were thousands of aftershocks in the three weeks after the main shock, and it was a year later when the aftershocks were no longer noticed.

Seward Hwy 64 Quake
The Seward Highway, March 28, 1964

Color graphic courtesy of Live Science, photos courtesy of the University of Alaska Archives.