Environment

20-story-tall megatsunamis pose a real danger, scientists warn

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Megatsunamis, could pose an increasing threat, as illustrated here by AI
Megatsunamis, could pose an increasing threat, as illustrated here by AI
Tsunami warning sign
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Damage from a tsunami in Indonesia
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Polar icecap melt has been towards the top of the worry list of the climate-conscious for years. Ocean levels have risen an inch and a half (3.8 cm) in the last decade alone as tens of trillions of gallons of freshwater melt into the oceans each year. Scientists have recently warned that melt might be just one of our concerns as megatsunami waves can give 330-ft-plus (100-m-plus) rise to the ocean in a matter of minutes.

Tsunamis – from the Japanese word "tsu," meaning "harbor" and "nami," meaning "wave" – are massive waves caused by the sudden displacement of water from landslides, volcanos, earthquakes, etc. They can reach speeds over 500 mph (800 km/h) and travel across entire oceans before reaching land and causing unprecedented destruction and flooding to anything in their path.

And like the name says, megatsunamis are especially large tsunamis, generally triggered by huge chunks of falling ice, rock, or dirt into the ocean causing massive waves. Even underwater shelf collapses can cause these 500-ft (150-m) waves to strike with little warning.

Tsunami warning sign
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Unlike normal waves that are on the surface and caused by wind, tsunamis are long waveforms that affect the entire ocean, from the surface to the sea floor as they travel along their destructive path.

The day after Christmas in 2004, a massive underwater earthquake off the coast of Sumatra, Indonesia – registering between 9.1 to 9.3 on the Richter scale, making it the third largest 'quake ever recorded – set off a tsunami with a wave measuring 167 ft (51 m) tall – nearly the height of a 17-story building – causing death and destruction to 14 neighboring countries. The tsunami reached as far as East Africa over 3,600 miles (5,900 km) away.

Damage from a tsunami in Indonesia
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In 1958, in Lituya Bay, Alaska, an earthquake thought to be between 7.8 to 8.3 shook a landslide into the water so big that it was heard 50 miles (80 km) away. Trees 1,719 feet (524 m) up the mountainside across the bay were hit with salt water from the megatsunami. Since 1854, Lituya Bay has had four megatsunamis that have measured over 100 ft (30 m) tall.

Roughly 8,200 years ago, there was an event known as the Storegga slide, a huge underwater landslide located off the coast of Norway that saw about 180 miles (290 km) of coastal shelf collapse. There's evidence that shows a 65-ft (20-m) tsunami, triggered by the Storegga slide, may have wiped out a significant portion of the coastal population of what is now Britain, about 700 miles (1,100 km) away.

With global temperatures on the rise, glaciers are melting and receding, exposing unstable mud and rock below. And with the Earth's tectonic plates ever-shifting, places like Greenland are experiencing considerable megatsunamis as huge chunks of ice and earth break away and fall into the ocean from the steep coastal cliffs.

On September 16, 2023, a mass of rock the size of a football stadium suddenly broke away from about 200 ft (60 m) up, carrying debris and glacial ice over 1,000 ft (300 m) down the 40° slope before crashing into the ocean causing a splash over 650 ft (200 m) high before turning into a roughly 200-ft (60-m) tall wave 6.2 miles wide (10 km) within the Dickson Fjord in eastern Greenland.

The wave sloshed back and forth for over a week. Seismology equipment 3,106 miles (5,000 km) away felt the event as well as the aftereffects of the sloshing seiches for a week.

With technology ever improving, tsunami early warning systems have made an impact in saving lives. Companies have even gone so far as to build floating tsunami survival pods and "tsunami-proof" houses. Even AI has some skin in the game with rogue wave detection ... which technically aren't tsunamis, but the technology is there. AI has also been used to predict flood paths from these powerful waves.

Nothing tops tsunami safety more than living atop a mountain, far, far from the coast though.

Source: Geo Science World

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9 comments
guzmanchinky
My goodness, but the chances are so infinitesimal as to be ludicrous. I should start a company that makes personal helium balloon escape pods!
vince
M<any enormous tsunami's like the one created when the big volcano on the island of Crete blew up around 1650 B.C. and caused 120 waves to hit most of what is present day Egypt, Palestine, Israel, Lebanon, Syria, Turkey, etc and wiped out the Minoan Civilization which existed at the time. MT Etna blew up in about 8,000 years B.C. and made an even worse flooding of the entire Mediterranean coastal range. Then future large volcano's blew up in the Mediterranean seas often foment livid stories to feed religious zealots that live on for thousands of years. Almost all the fictitious stories like in the Bible with the great flood and Noah's ark results from not rain but from tsunami's.
FreddyB
That is a very misleading AI image. In general, a tsunami does not generate breaking waves. If you've seen videos, it appears as a ever growing rise in the sea level. One feature is that the sea level first decreases and then increases with the arrival of a tsunami.

For another catastrophe that can keep you up at night, a super tsunami may also happen if the cliffs off of Portugal ever give way. The east coast of the US and probably the rest of the east coast of the north and south American continents would be 'toast.'
Jinpa
One thing wrong with the AI-generated image of a super tsunami is that it would have sucked the beach dry at least minutes before the big wave gets there.
aksdad
Are summer ice melt, calving glaciers, and mud and rock slides from melting glaciers a new thing? I thought they'd been happening since the beginning of the latest interglacial warm period, starting about 12,000 years ago.
Jinpa
I think I remember a scene from James Michener's book abut Alaska describing a tsunami chasing some people up a rather high hill.
Leonard Erdman
The article should have mentioned the island of LA Palma in the Canary Islands. A 6 foot wide ridge bisects the island. This ridge was created by the movement of the island over the vent feeding the volcano Cumbre Vieja. Geologists have estimated that if the island west of this ridge slides into the Atlantic it will comprise of 500 billion tons of earth and rock. Now that would be a mega tsunami wiping out the East coast of the United States.
Eggster
@FreddyB Thanks for bringing that up. Tsunamis are frequently depicted as cresting waves, but all of the video footage that I have seen shows them to be more like 'surges' of water akin to the water in a bowl when it is tipped.
BlueOak
You don’t get funding or attention by acknowledging “never mind, it’s all OK.”