Massive Alaska megatsunami was second largest ever recorded
A massive ‘megatsunami’ wave created when part of an Alaskan mountain collapsed into the sea is the second highest wave ever recorded and is a reminder of the risks posed by melting glaciers, scientists say.
Last summer, a giant wave swept through a remote fjord in southeast Alaska, leaving destruction in its wake.
The incident went largely unreported at the time, but a new scientific analysis shows it was caused by a massive landslide.
An incredible 64 million cubic meters of rock, the equivalent of 24 Great Pyramids, splashed into the water below. The sheer force of this amount of rock falling into the fjord in less than a minute created a massive wave almost 500 meters high.
Researchers say the fact that the incident occurred only in the early morning hours prevented the destruction of tourist cruise ships.
Seeing the damage in Tracy Arm Fjord with his own eyes, Alaskan geologist Dr. Bretwood Higman said it was a “close possibility.”
“We know there are people who are almost in the wrong place,” he said. “I’m quite afraid we won’t be so lucky in the future.”
Tracy Arm in Southeast Alaska is known for its sheer cliffs and icy terrain [BBC]
These huge waves, called megatsunamis, occur when an earthquake or landslide caused by loose rock crashes into the water below. They are usually localized and disperse rapidly.
Other types of tsunamis occur in the open ocean and are triggered directly by earthquakes or, occasionally, other powerful events such as underwater volcanoes.
These, like the Japan tsunami in 2011, can travel thousands of kilometers and hit populated areas, causing widespread destruction and loss of life.
The largest megatsunami occurred in the 1950s and was over 500 meters high. This last megatsunami was the second largest megatsunami.
[BBC]
Dr Higman arrived on the scene just weeks after the tsunami hit the Tracy Arm Fjord, popular with cruise ships exploring Alaska’s natural wonders.
He found broken trees strewn across the mountainside and thrown into the water, and large fragments of scarred rock stripped of soil and vegetation.
Alaska is particularly vulnerable to megatsunamis because of its steep mountains, narrow fjords, and frequent earthquakes.
New research has now been published Science suggests that glacial melting caused by climate change is making such collapses much worse.
The team combined fieldwork, seismic data and satellite data to reconstruct a domino chain of events and track the height of the wave.
from University College London. Stephen Hicks said the glacier had previously “helped retain this piece of rock” and so when the ice retreated it exposed the base of the cliff, “allowing the rock material to suddenly collapse into the fjord”.
He and his colleagues have been studying tsunamis for decades and are concerned.
“More people are now going to remote areas – often these tourist trips to see the natural beauty of the area to learn more about climate change – but they are also dangerous places.”
Ground-level view of tsunami damage near the mouth of the fjord shows uprooted trees and vegetation stripped from the shoreline. [Photo by Cyrus Read/U.S. Geological Survey.]
Dr Higman said there was little doubt that megatsunami risks were increasing.
“I’m pretty sure at this point they’ve increased not just a little bit, but a lot,” he said.
“Perhaps 10 times more frequent than just a few decades ago.”
Scientists are calling for broader monitoring of hazards in parts of Alaska that may be vulnerable to megatsunamis.
Some cruise lines have announced they will stop sending ships to Tracy Arm due to safety concerns.
