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Wednesday, May 16, 2018

DAY 14: Lava Bombs 500 Feet in the Air

Well, anyway, that was the headline in a Forbes article on the subject.  The number of fissures is up to 21, the latest in Lanipuna Gardens.

While lower Puna is where people are affected, those ash plumes uphill from Halemaumau are now shooting up to 12,000 feet. Below, yesterday:

However, don't worry about mega-tsunamis from the current eruption, for Cindi Preller from the Pacific Tsunami Warning Center said, yesterday:

For the big ones, we worry they would occur off of the southwest flank of Mauna Loa.

Interestingly enough, I made a search and found a 5-minute National Geographic clip featuring Gerard Fryer, who at that time (he looked younger) was a colleague of mine at the School of Ocean and Earth Science  and Technology, detailing a mega-tsunami from that very location.  Worth a look.  Last I heard, he had moved to the Pacific Tsunami Warning Center.  

Fourteen years ago, with colleagues from the University of Hawaii and elsewhere, he reported on a possible mega-tsunami from the Alika Slide around 120,000 years ago, causing a mega-tsunami with indisputable evidence found on other Hawaiian islands to run-up elevations exceeding 1000 feet.  The key is that mega-tsunamis only occur from landslides, not major earthquakes in the ocean.

The one historic exception is that just about 60 years ago, there was a 7.8 earthquake in Lituya Bay, Alaska, causing a landfall which displaced water, resulting in a mega-tsunami of 1710 feet.  Bill and Vivian Swanson on their fishing boat saw everything and survived.

However, the standard mega-tsunami is an island landfall of monumental speed and volume causing a tsunami more than 100 feet high in the far field (1000 kilometers or 620 miles).  The largest ocean tsunami should not create a tsunami exceeding 35 feet, which was about that high in Hilo in 1960.  The Great Tohoku Earthquake and Tsunami in 2011 with a 9.1 earthquake reached 133 feet, but that was in the near field.  In Chile, 11,000 miles away, the tsunami got up to 6.6 feet.

However, the science is not all that well-known, for the April first 1946 Aleutian Islands earthquake of from 7.1 to 8.6 (still being studied) caused a wave of 45 feet in Hilo.  Tsunami researchers have been searching for the subsequent underwater landslide that was the real cause, and have not yet succeeded.  Freyer is mentioned in this article.

Every few years the notion of mega-tsunamis pop up in the media, usually induced by Professors Simon Day of University College in London and Steven Ward of the University of California at Berkeley.  Their target of opportunity are the Canary Islands.

When I wrote SIMPLE SOLUTIONS for Planet Earth I took my stab at this fantasy, and originally titled the chapter Five Hours to Los Angeles.  Then I learned that the Continental Shelf might diminish the affect.  However, there is a convenient open channel to Seattle.  Thus, my upcoming novel on Six Hours to Seattle.  Sure, the landslide from the other side of the Big Island is the standard fear, but I found potential rift zones around Hilo that sufficed for my purposes.

I worried about how my wife, who grew up in that town, and her relatives, would react.  And there are a lot them there, for a Nakamichi-Onishi reunion picnic can draw 200 people.  However, the potential is so low that no one cared.

A tsunami moves at the speed of 500 MPH, about that of a fast commercial jet aircraft, so the passengers would see the event beginning and ending.  But, to be scientifically correct, the odds of a mega-tsunami striking Seattle from a Hilo landslide are so low as to be laughable.  However....


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