Climate threatsThe World's Biggest Waves: How Climate Change Could Trigger Large Landslides and “Mega-Tsunamis”
Natural hazards which are triggered, made more frequent, or exacerbated by climate change can’t be prevented, but damage to infrastructure and populations can be minimized. This can be achieved through scientific understanding of the physical processes, site-specific engineering risk analysis and coastal management of hazard-prone regions.
Just over 60 years ago, a giant wave washed over the narrow inlet of Lituya Bay, Alaska, knocking down the forest, sinking two fishing boats and claiming two lives.
A nearby earthquake had triggered a rockslide into the bay, suddenly displacing massive volumes of water. The large landslide tsunami reached a height of more than 160 meters and caused a run-up (the vertical height that a wave reaches up a slope) of 524 meters above sea level. For perspective, imagine run-up to about the height of the CN Tower in Toronto (553 meters) or One World Trade Center in New York City (541 meters).
Large landslides, like the one that hit Lituya Bay in 1958, are mixtures of rock, soil and water that can move very quickly. When a landslide hits a body of water, it can generate waves, especially in mountainous coastal areas, where steep slopes meet a fiord, lake or reservoir. Although mega-tsunamis are often sensationalized in the news, real and scientifically documented events motivate new research.
In late July, a 7.8 magnitude earthquake near Perryville, Alaska, triggered a tsunami warning for south Alaska, the Aleutian Islands and the Alaskan Peninsula. And scientists recently warned that a retreating glacier in a fiord in Prince William Sound, Alaska, had elevated the risk of a landslide and tsunami in a popular fishing and tourism area not far from the town of Whittier.
International research efforts are urgently underway to better understand these major natural hazards. This is critically important, since climate change could contribute to increasing the number and size of these events.
Recent Giant Wave Events
Triggered by either an earthquake or higher than normal rainfall, another massive landslide occurred in Alaska in 2015. This one was in Taan Fiord, 500 kilometers east of Anchorage. This event was so powerful, it released an enormous amount of energy and registered as a magnitude 4.9 earthquake, approximately equal to the explosive force of 340 tons of TNT.
The landslide impact into the water was so strong that it generated seismic signals that were detected at monitoring stations in the United States and around the world. The impact generated a wave with a run-up of 193 meters. Thankfully, the area is remote and no one was killed.
