August 24, 2004

Plinian eruptions are at the upper end of a volcanic eruption spectrum. Ejecting at a velocity of over 1000 mph, the ash columns in a Plinian eruption may reach 30 miles in height. Mt St Helens, during the first several hours, was a classic Plinian eruption, producing an 80,000 ft ash cloud, bizarre ash mammatus, and memorable eyewitness reports. They've been a subject of numerical simulations. Researchers speculate they may have been a factor in the Dark Ages.
  • Gee, I had a plinian eruption just the other...uh, never mind. (Interesting post, by the way)
  • great post roly!!
  • ash! i remember that. lived in montana during the mt. st. helens eruption, and we had to wear bandannas across our faces to keep from breathing in the weird gray "snow" we were getting. it was really odd, i think we got maybe an inch or less, but still. how often do you get a blanket of cooled volcanic cinders in your front yard? flew into vancouver a month or so ago, and actually saw mt. st. helens from the air. complete with the now-deformed cone at the top. there were other mountains to see too, you could pretty easily tell the volcanic ones because of the increased height and more conical shape. from what i saw, and what i've heard about potential mudslide damage, seattle better hope that mt. rainier doesn't decide to blow ash any time soon...
  • i come from montana, i wear a bandana, my spurs are of silver, my pony is grey...
  • i find this all very sexual.
  • ugh, doomsday is so depressing.
  • Uh, I could be wrong, but the Dark Ages weren't called that because it was dark, rather because we know relatively little due to the lack of written data. What do volcanoes have to do with that, Mr Wohletz, eh?
  • Re: Dark Ages As I recall from some PBS/Discovery Channel/History Channel special, the idea is that there were temporary (on a geologic scale) climate changes caused by eruption. The collapse in foodstocks forced some people (the goths?) off the Mongolian steppe into Europe. The same shifts caused massive crop failures in Europe, all leading to the final collapse of the already weak Roman Empire (Western and Central Divisions), thus leading to the Dark Ages. The last links hints at this, but you'll have to connect the dots on your own when trying to figure out which people got displaced to where and subsequently killed off/conquered which other people. But I'm not really too sure. I'm too busy at work to do a fact check.
  • Oh man, I remember the St. Helen's eruption vividly. I was living about 4 - 4.5 hours away. When it blew, it sounded like our own roof was blown off. Remember, we were about 240 miles away. That's how loud and powerful the repurcussion was. It was truly scary. That entire day, it was so eerily silent. Almost as if the mountain had literally sucked the sound from the air. I guess that the ash was absorbing a lot of sound. The birds didn't make a single noise. We noticed that first, we lived in the woods and it felt so strange outside. My mom and I were gardening and all of a sudden we both stood up and looked at each other and without a word went back into the house. I guess the ash was really started to hit us. What a god-awful mess that was.
  • I believe that Dark Ages also referred to an intellectual dark age, brought about not only by the economic turmoil but also the influence of the Catholic Church to consolidate its power. I'm not sure though how true that was during the early Dark Age period... maybe someone else can comment.
  • No - the Catholic Church was a beacon of intellectual activity. But their monastaries kept getting burned by Vikings and the books torn up for the gold on their bindings.
  • Point well taken, but weren't the sciences (astronomy, physics, etc) at a standstill until the Renaissance? I grant that music and religious literature did flourish. Just trying to learn more about your point.
  • re the Dark Ages, which is a bit of a historical "mis"nomer, they should really be called the Early Medieval Period (harump!) also dark due to the withdrawal of roman garrisons from outpost colonies in greater gaul/celtic area...after 300 years of roman overlord protection the "natives" were in little position to defend themselves from the invasions of germanical types and ensuing chaos... however, I must say I found the first sentence in the last link "Modern history has its origins in the tumultuous 6th and 7th centuries." a bit...well...how does one say??? um, not quite VALID... rome anyone?
  • i don't know about the steppes of europe, but man i remember when the jocks forced the goths off the steps of the high school back in '89. that was a bad time to be wearing black and being all depressed and stuff.
  • rome anyone? When Krakatoa blew around 535, it caused climatic cooling which triggered massive crop failure, famine and rapid spread of plague in dozens of outbreaks over the next 200 years. Plague traveled along Roman trade routes, each time killing off more imperial citizens, resulting in an ever-shrinking tax base and army. The Slavs got all het up and began plundering Roman territory and killing imperial citizens in several massive invasions between 540-570. Several other tribes and tribelets invaded Roman territory and/or demanded protection money. Which meant less gold in the Roman treasury and even fewer citizens to pay taxes and protect the empire. And meanwhile the plague hit again and again. Civil war broke out in Constantinople around 602, and the Persian War came soon afterwards. By 618, 3/4 of the Roman Empire was gone and the government was pretty much bankrupt. By 720 the Arab Caliphate was the biggest power in the Middle East and Mediterranean, and the Roman Empire was smaller than modern-day Turkey. It held on for a long time afterwards, but only at a fraction of its former power. Re: "dark" ages, the literal dark came first (volcanic ash blocking the sun), then the metaphoric dark of a few centuries of plague, famine and political upheaval. Seriously, check out Catastrophe: An Investigation into the Origins of the Modern World. It's the best book I've read in years. Frogs: hee hee!
  • Now I've learnt two new words: mammatus and tephra. And I have by no means read everything in these links yet. Thanks, rolypolyman! [banana]