Posted on 10/18/2017 9:44:56 AM PDT by JimSEA
When volcanic mountains slide into the sea, they trigger tsunamis. How big are these waves, and how far away can they do damage? Ritter Island provides some answers.
Early one March morning in 1888, a 4-cubic-kilometer chunk of the Ritter Island volcano collapsed into the Bismarck Sea northeast of New Guinea. This volume of land was about twice that of the Mount St. Helens landslide in 1980, and it is the largest historically recorded tsunami-causing volcanic sector collapse.
The ensuing landslide triggered a tsunami tens of meters high. The waves were still 8 meters high when they reached parts of the island of New Guinea that are several hundreds of kilometers away, according to observers who witnessed the event [Ward and Day, 2003].
Volcanic islands are the source of some of the world’s largest landslides. These landslides have the potential to generate large tsunamis. Scientists have debated the magnitude of these tsunamis, but much uncertainty remains over landslide dynamics and how far a tsunami can travel across an ocean basin while remaining large enough to cause damage.
(Excerpt) Read more at eos.org ...
The displacement of the landslide material generates a 900 m high dome of water above the descending slide block after 2 minutes. From 10 to 20 minutes the neighboring Canary Islands have been inundated to several hundred meters height. The waves approach the Western Sahara over the next hour as waves 50-100 m stack together and sweep ashore (Ward and Day, 2001).
The brunt of the tsunami traverses the Atlantic Ocean basin, growing in width over the next 5 hours. The coast of western Europe receives 5-7 m waves. Meanwhile, 15-20 m waves strike northern South America while 10 m waves buffet Newfoundland. Along the shallow passive margin of Eastern North America, the tsunami builds to 20-25 m just prior to landfall around 8 hours. Within 11 hours, the Caribbean, North Atlantic, Gulf of Mexico, and Central America have been impacted by direct or diffracted tsunami waves (Ward and Day, 2001).
The effects of such a sudden event would be devastating, with the populations of the Canary Islands and the coastal areas of Africa decimated. In Europe and South America, warning time would be greater but likely still insufficient to evacuate the coastal areas. The most publicized effect of such a wave would be that on the Eastern seaboard of the United States. The tsunami would impact most coastal areas within 8 hours of La Palma�s collapse. Even with the maximum warning time, it is highly unlikely that all areas at risk for inundation could be sufficiently evacuated. In some cases, the best escape may be vertical, with high rises in New York, Boston, and other port cities used to escape the rising waters.
I have heard the suggestion that people in these areas might want to keep a hot air balloon stored in the garage. Probably even better than a high rise. Or you take your chances.
Plausible. There was a recent study which tried to debunk the threat, but I think the numbers are a fair estimate.
Just to say:
“La Palma volcano: Canary Islands hit by 40 tremors in 48 hours. La Palma, one of the Canary Islands, was hit by a series of mini-earthquakes at the weekend, measuring between 1.5 and 2.7 on the Richter scale.Oct 11, 2017”
And from yesterday, October 17th:
“Canary island La Palma experiences 352 earthquakes in ten days as scientists continue to monitor its active volcano
“Canary-island-La-Palma-sees-352-earthquakes-ten-days.
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Should the East Coast be worried?
Yes, no panic but they should at least post tsunami escape routes.
They are not ruling out the tsunami possibility, just saying it’s very unlikely. I’d agree. However, localized tsunamis caused by landslides have happened in Alaska. Luckily they were contained by the bays and coastal islands where they happened. The slippage of the Northwest American subduction zone has created tsunamis that did a lot of damage to Japan.
Las Palmas would be most likely if the volcano explosively erupted sideways (like St. Helens). Not a big chance but the likelihood isn’t 0.
Yup. I read that some researchers suspecting a (earthquake) tsunami in the northwest in 1700 confirmed their suspicions by reading some Japanese history about a tsunami in 1700.
There are huge ancient underwater landslides around the Hawiian Islands.
Here:
Giant Landslides of the Hawaiian Islands
The Hawaiian islands have a geological history of volcanic flank collapse creating a tsunami. The Australian coastline has indications of debris deposited above 1100 foot above sea level attributed to such an episode.
Wow!
Doesn’t one of the Hawaiian islands have a HUGE crack that geologists believe could break off, causing massive tsunamis?
Got my curiosity up, went and looked it up.
The “crack” is on the southern edge of Kilauea Volcano, on Hawaii, the Big Island. About 10% of the island is slipping into the ocean along what they call the Hilina Slump. Apparently it is about 5000 cubic miles of “stuff” slipping about 10 cm/year. In 1975, it slid 11 feet, making the “crack” 26 FEET wider along a 37 mile long stretch!
One source (http://www.science-frontiers.com/sf115/sf115p09.htm) says, “If the entire 4,760-cubic-mile block decided to break off, it would probably create a magnitude-9 quake and a tsunami 1,000-feet high. All the coast-hugging cities of the Hawaiian Islands would be swept away. And LOOK OUT Australia, Japan, and California.”
Wow. How far inland? I grew up on the Oregon coast, and we got to 1100 feet fairly quickly—I’d guess about 10 miles inland— but I am back east now and about 1600 feet probably a thousand miles inland.
Note: this topic is from . Thanks JimSEA.
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Wow!
See the map a Comment #8. It shows a lot of the slides have occurred on the southern edge of the Big Island. A few years back I think it was CSI Miami had a show which involved just such an event. A chunk of land slid off one of the islands—Canaries or Azores and sent a 20 foot high wall of water into Miami. Their murder case was not caused by the tsunami, but it complicated matters a lot.
I remember that one! Horatio weathered it in a bank vault, IIRC.
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