Tsunamis, climate, seamounts and impending disaster ... !
There have been a number of articles floating around the popular press for the last week that I thought I would touch on briefly ... always fun to decipher the real news from the hype.
Active fumaroles on Datun Mountain in Taipei.
- An article out of the Taipei Times suggests that the city of Taipei in Taiwan is in great peril from Datun Mountain/volcano. The volcano, which was previously thought to have erupted ~200,000 years ago is now thought to have erupted only 5,000 years ago. That 195,000 years really does make a difference in terms of worrying about potential future eruptions, but there are few details about what sort of eruption there might have been 5,000 years ago (beyond the TV reports that "NTU professors said that if Datun erupts, its impact would be even worse than the devastating 921 Earthquake." Nothing like some good fear mongering.) They also attribute any seismicity today to "cooling magma" for what its worth - however, with any volcano with active fumaroles (above), the idea that it could still be considered "active" is no surprise.
Another article makes it seem that the potential for a future eruption from the volcano is low, but the mayor of the city still plans to construct a contingency plan if the volcano reactivates (which is still a good idea). Meanwhile, the GVP page on the "Datun Volcanic Group" suggest that the volcanic region was active as recently as the Pleistocene (<20,000 years ago). Most of the group are andesite stratocones or domes.
- The New York Times has a report on the potential tsunami generated by the great Thera eruption between 1630 and 1570 B.C. The eruption likely generated a tsunami that swept across eastern Mediterranean Basin. These findings are based on sediments found at excavations on the shores of the Mediterranean in Israel. Although it is not shocking that an eruption the size of the Minoan eruption at Santorini/Thera would produce a tsunami, finding evidence of the wave is always nice to back up the theory.
- A deep sea expedition to the Casablancas seamount 300 km off Morocco in the Atlantic has turned up evidence for fresh eruptions from the seafloor volcano. What appears to be fresh lava flows and craters were discovered by the submersible HyBIS. Of course, the submersible was at the seamount in hopes that there was life - not fresh evidence of eruption - which shows you can never guess what you might find in explored regions at the seafloor.
- I stumbled across this excellent image of El Misti (the volcano) and Arequipa (the city) in southern Peru. It shows clearly how close to the active volcano the city of over 1 million people is creeping. El Misti last erupted in 1985, producing a small (VEI 1) explosive event, with the last known significant eruption in 1784.
- Finally, there has been a lot of discussion in the comments by readers about the study have claims that a mystery volcanic eruption might have played a significant role in climate during the early 1800s. It definitely is a quandary how such a prominent SO2 signal could be found both in ice from Antarctica and Greenland yet no obvious candidate for an eruption easily identified. However, remember that even in 1809-1810, great swathes of the world were unpopulated and unseen, so an eruption such as the Kasatochi eruption in the Aleutians, which released huge amounts of sulfur dioxide last year, might have never been recognized due to its remote location. The same might be said for eruptions along long stretches of the Andes in Chile. There are multiple, uncorrelated spikes in the sulfur dioxide record in the ice cores over the past few thousand years, which makes it all the more interesting to determine what volcanoes might be hiding significant eruptions in the relatively recent past.