السواحل و المراسي ستضرر لكن ما حجم الخطر على سكان المدن
حسب ما قرأت تم تفنيد نظرية حدوث ميغا تسونامي
I'm assuming this is in relation to various doomsday like scenarios floating around the internet and popularized in at least a few documentaries that a "megatsunami" might be generated by a flank collapse of La Palma which could impact the eastern US and western Europe? The origin of these overblown claims largely comes from
Ward & Day, 2001. As highlighted in a variety of different subsequent studies, this analysis was deeply flawed and the purported risk of large scale tsunamis that could impact the US or Europe is grossly misrepresented. There are two main issues with the original Ward & Day paper (1) the assumption of a complete, essentially instantaneous flank collapse and (2) the details of the tsunami modelling. For the first, the geologic record of flank collapses of oceanic stratovolcanoes highlight that large ones are exceedingly rare (e.g.,
Pararas-Carayannis, 2002). Perhaps more importantly, detailed work on the deposits resultant from these, including a set associated with the Canary Islands (e.g.,
Hunt et al., 2013) highlight that these are typically multistage collapses, i.e., not everything slides in at once. Because the size of the tsunami scales with the volume of material displacing water, a multistage failure will not produce any where near the same size of tsunami as a single, large failure. Even assuming a single, large failure, the details of how the slide and resulting tsunami waves are modeled has large implications for the scale of the modeled tsunami that is generated. Several other modelling efforts of a large flank collapse of La Palma have highlighted that the predictions from Ward & Day are extremely exaggerated (e.g.,
Nieuwkoop, 2007,
Lovholt & Gisler, 2008). Both of those papers highlight that a major flank collapse of La Palma could certainly generate dangerous tsunami waves for residents of the Canary Islands, but the chance that such an event could generate large tsunami waves that would have major impacts in Europe or the US is extremely unlikely. Dave Petley, who studies landslides and spends a lot of time trying to improve the communication of landslide hazards to the public, provided a nice summary of this all in
his blog back when the Hunt paper came out. EDIT: Apparently Dave did a
followup because the false rumors of a major flank collapse from La Palma potentially causing a devastating megatsunami refuse to die. EDIT 2: There is even a third set of two posts from Dave,
here and
here further trying to dispel this myth.
In short, the possibility of a megatsunami from a flank collapse of La Palma that would impact the US or Europe was grossly misrepresented by an early paper, which despite being proven wrong multiple times in multiple different way, the popular media has kept this particular "natural hazards ghost story" alive for the better part of 20 years. There is a real risk of tsunami from a flank collapse, but mainly if you live in the Canary Islands. So, if you live in the Canary Islands, then yes, caution is warranted both for the potential of an eruption or possible earthquakes or tsunamis associated with a possible eruption and you should be closely monitoring reputable sources of information (like
INVOLCAN). If you do not live in the Canary Islands, then no, you probably should not be worried, and you should stop perpetuating this misguided idea.