We're talking about the kinds of eruptions that hurl ash and pumice so high and so far that the landscape for hundreds or thousands of miles around is blanketed in thick, choking ash. We're talking about eruptions that bury landscapes for hundreds of square miles in pumice fields tens of feet thick.
We're talking about the kind of eruption whose traces are still fresh and clear more than seven thousand years later.
|Road cut through Mount Mazama pumice, Route 58|
Perspective time. I'm standing in a place where, if I'd been able to stand still during the fallout from the eruption, I'd have been over my head in pumice. Over thirty miles away, not in the path of any lahars or pyroclastic flows or any such excitements, and if I'd had a one-story house, it would have been buried to the eaves. And, people, these aren't itty-bitty bits of pumice. Stuff landing here reached up to nearly two inches long.
|Mount Mazama Pumice, collected at the road cut on 58|
It's difficult to imagine. We just haven't had many events like that in our living memory. In fact, when my intrepid companion and I got to talking about caldera eruptions the other day, I had to ask Erik Klemetti when the last one was. Mount Pinatubo fits the bill: maclargehuge eruption with worldwide consequences that left a caldera nearly two miles across. Note that Erik called that a "small" caldera collapse! It's the closest to Mount Mazama we've come in the information age.
Then there was the Valley of 10,000 Smokes. Krakatau. Tambora. That last was the largest eruption in recorded history. I mention this because Pinatubo was a measly VEI 6. A piddly little colossal eruption. Mount Mazama, on the other hand, rated up there with Tambora: a VEI 7. Super-colossal.
And it has left its mark, so far away.
|Mount Mazama Pumice mixed with cinders. I should get a centimeter scale tattooed on my thumb, shouldn't I?|
|Mount Mazama Pumice and cinders at top of cut|
And as you stand there, you ponder the force it takes to create a landscape like this, and your poor brain boggles. Thing is, this is only the beginning. By journey's end, you may just feel you've experienced a caldera eruption inside your own skull.
Ye olde indispensable references:
Roadside Geology of Oregon: Especially the marginalia, oddly enough.
Erik Klemetti: My go-to man for all things volcano, even on a Sunday, even on a holiday weekend.
Anne Jefferson: Who is not just a master of floods, it turns out, but knows some kick-ass volcanoes such as Fernandina.
Lockwood DeWitt: Tour guide of Oregon geology extraordinaire, and without whom I wouldn't have known what the hell I was seeing.