Megatsunami

Lituya Bay megatsunami diagram (English)

Lituya-Bay-overview-with-arrows

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Survey of megatsunami runup damage Taan Fiord 9 August 2016

Megatsunami refers to an extremely large wave caused by a large-scale disturbance, such as a meteorite impact, volcanic eruption, or more commonly, a massive landslide. These waves far exceed the size of those formed by any other means, including earthquake-induced tsunamis, and can reach heights of hundreds of meters, causing catastrophic destruction along coastlines.

Causes

Megatsunamis are primarily caused by events that displace a significant volume of water. These include:

• Landslides: Large landslides, either subaerial or submarine, can displace vast amounts of water. An example is the Lituya Bay megatsunami in 1958, which was caused by a massive landslide triggered by an earthquake, resulting in a wave that reached a record height of 524 meters (1,720 feet).
• Volcanic Eruptions: Significant volcanic events can lead to megatsunamis by collapsing the volcanic structure or causing massive landslides. The collapse of the Santorini caldera around 1600 BCE is believed to have generated a massive tsunami affecting the entire Aegean Sea.
• Meteorite Impacts: Although rare, large meteorite impacts in the ocean can generate megatsunamis, displacing huge volumes of water. The Chicxulub impactor, which is linked to the extinction of the dinosaurs, is an example of such an event.

Effects

The effects of a megatsunami can be devastating, with the potential to obliterate entire coastal regions. The impact includes:

• Massive Flooding: The initial wave and subsequent waves can flood vast areas, destroying buildings, infrastructure, and natural landscapes.
• Loss of Life: The sudden and extreme nature of megatsunamis can lead to high death tolls, as was the case in Lituya Bay, where fortunately, the area was sparsely populated.
• Long-term Environmental Impact: The ecological and environmental damage can last for years, affecting marine and coastal ecosystems.

Historical Examples

• Lituya Bay, 1958: The most well-documented megatsunami, which occurred in Alaska, USA. A large landslide caused by an earthquake generated a wave that stripped trees and soil from the slopes of the bay.
• Santorini Caldera Collapse, circa 1600 BCE: The ancient eruption and subsequent caldera collapse is believed to have caused a massive tsunami, significantly impacting the Minoan civilization on the island of Crete.

Preparedness and Mitigation

Due to their rare and unpredictable nature, preparing for megatsunamis is challenging. However, strategies include:

• Monitoring of Potential Sources: Keeping an eye on unstable volcanic islands and regions prone to large landslides can provide early warning signs.
• Tsunami Warning Systems: Expanding and improving tsunami warning systems to detect unusual wave patterns can offer some advance notice.
• Coastal Planning: Implementing zoning laws that prevent the development of vulnerable coastal areas can reduce the impact of a megatsunami.

See Also

• Tsunami
• Natural Disasters
• Volcanic Eruptions
• Meteorite Impacts