Posted on 10/04/2015 7:00:40 PM PDT by SeekAndFind
Waves the size of the Chrysler building may seem like they belong in a movie trailer, but scientists have recently found that megatsunamis are all too real.
Scientists say that 73,000 years ago, a large flank (or slope) from the volcanic island Fogo in the Cape Verde islands off the coast of Africa fell into the ocean and triggered a tsunami that could – quite literally – move mountains.
“You’re displacing a huge mass, which must generate movement of water,” Ricardo Ramalho, the lead researcher behind the study, told The Washington Post. “And in the case of volcanic flank collapses they can be very acute, because you have all the mass collapsing basically into the oceans.”
Waves the size of the Chrysler building may seem like they belong in a movie trailer, but scientists have recently found that megatsunamis are all too real.
Scientists say that 73,000 years ago, a large flank (or slope) from the volcanic island Fogo in the Cape Verde islands off the coast of Africa fell into the ocean and triggered a tsunami that could – quite literally – move mountains.
“You’re displacing a huge mass, which must generate movement of water,” Ricardo Ramalho, the lead researcher behind the study, told The Washington Post. “And in the case of volcanic flank collapses they can be very acute, because you have all the mass collapsing basically into the oceans.”
So what was Dr. Ramalho’s proof for a megatsunami? Rocks. Really, really big rocks.
When Ramalho was on Santiago in 2007, he found large boulders on top of a high plateau, near a sheer, vertical cliff. Ramalho and his colleagues were able to trace the boulders’ origin to the cliff below because the rock types “exclusively crop out on the cliff faces and lower slopes of the plateau,
(Excerpt) Read more at csmonitor.com ...
They’ve been saying the same thing about Cumbre Vieja - it could wipe out the Eastern seaboard of the USA. Funny thing is, it slipped a few yards in the 1950’s but did not fall into the ocean.
And you can bet Brodhi will be there riding it with Johnny Utah on his tail.
I forgot to add “100% pure adrenaline!”
Steven N. Ward
Institute of Geophysics and Planetary Physics, University of California, Santa Cruz California, USA
Simon Day
Benfield Greig Hazard Research Centre, Department of Geological Sciences, University College, London, UK
Abstract:
Geological evidence suggests that during a future
eruption, Cumbre Vieja Volcano on the Island of La Palma
may experience a catastrophic failure of its west flank, drop-ping 150 to 500 km^3 of rock into the sea.
Using a geologically reasonable estimate of landslide motion, we model tsunami waves produced by such a collapse. Waves generated by the run-out of a 500 km^3 (150 km^3) slide block at 100 m/s could transit the entire Atlantic Basin and arrive on the coasts of the Americas with 10-25 m (3-8 m) height ...”
Actual paper is on pdf file.
Link here:
http://www.es.ucsc.edu/~ward/papers/La_Palma_grl.pdf
There's science for you ... "huge". Huge like a Stag Beetle? a galaxy? an ocean liner?
To me the relevant parameters are radius and amplitude. As a first guess, we might think that the height, or amplitude, of the wave might be a measure of its energy per unit length, on the basis of gravitational potential energy.
So this will diminish in proportion to the distance from the source. That leaves the question of how to evaluate the amplitude of a point source, which will diminish very quickly with distance. Perhaps there is some effective radius on the order of the width of the wave.
Generously supposing this radius to be 1 km, then we would expect the wave amplitude to be 1/100 the size of the Chrysler building at a distance of 100 km. And so on.
That's still a big wave!
Your post was a strange blast from the past for me. I took a class many years ago (mathematical seismology) from Dr Steve Ward. He was also on Coast to Coast AM briefly probably about ten years ago. Not sure if the guy has changed, but he was a real sob back in the day.
Where did you take the course?
What effect would that have on Donald Trump’s hair?
UCSC.
For the record, Ward was brilliant. One of those guys who eats PDE’s for lunch, but he’s also a one-trick-pony on this mega tsunami thing.
I take it you were a geology major. I was too back in the 80s. Came one geology course, plus a few dopey, but required, non-major liberal arts courses short of earning a BS in Geol. Long story.
Big rocks move over long periods of time thanks to gravity, tectonics, human activity, etc. Color me very skeptical.
There was a program a number of years ago on Nat Geo I believe that demonstrated how large chunks of vertical cliff breaking away and thus becoming high speed landslides can displace a huge amount of water.
They displace much more water than just the mass of the land itself, because of the speed at which the land falls into the water apparently also pulls air into the space where the water was very quickly.
They demonstrated this effect in a small scale tsunami tank in some university.
They then theorized that this explained how some fossils unique to the area of Hawaii were found at the top of some Australian mountains some 600ft up if I recall correctly.
But their general hypothesis was that high speed landslides are capable of creating massive waves that move at a high rate of speed and do not lose energy over very long distances.
A massive underwater uplift would be worse
When I lived in CO, the only weatherman we trusted was the one who opened the door to see if it was snowing.
Not the case apparently.
The highest wave height created by ocean floor displacement is about 50 ft. The wave is still incredibly dangerous and destructive due to the wave length, however.
The ones that hit Indonesia and such were only about 20 ft high, so a 50 ft tsunami would be the end of the world to anywhere struck by it.
High speed landslides are capable of creating taller and faster waves due to the energy they hit the water with and due to the amount of water rapidly displaced by both the land and the air that enter it.
I don’t think that these types of waves have the same incredible wavelengths of tsunamis though.
The high plateau around Twin Falls, ID was scrubbed of all topsoil when the dam holding back Lake Bonneville gave way. The flood data in that region are astonishing. “The flood emptied the top 107 meters of water from Lake Bonneville , an estimated volume of 4,750 cubic km of water. The peak discharge from the Red Rock Pass outlet is estimated to have lasted for about 8 weeks and to have been about 500 times that of the maximum discharge ever recorded from the Snake River at Idaho Falls.”
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