Various posts by Dr. Erik Klemetti, including this one, and this.
Jón Frímann Jónsson–an interesting though not expert lay source whom many of us online volcanophiles relied upon during the lead-in to the 2010 eruption of Eyjafjalljökull.
London Volcanic Ash Advisory Centre (VAAC) website. This should be the first place you check, if you want to know if Öræfajökull has really erupted. The link to Toulouse VAAC on this page is also helpful.
Featured image: Satellite image of Öræfajökull, showing cauldron of glacial meltwater in late 2017. Antti Lipponen, CC BY 2.0.
There has been a slight, but possibly very important, change in the eruption–less lava coming out in the Lower East Rift Zone and a hiatus in summit collapse events–and I’m updating the Kilauea eruption page again. Can’t spend a lot of time on it because of book work, but I’ll try to catch the important stuff. Right now it’s mostly waiting to see the next pronouncement from USGS/HVO.
Click the link at the upper right of this page or use this one.
You’ve seen plenty of video of the lava flowing in the LERZ, so here is a USGS video of a summit collapse event about two months into the eruption. It’s not dramatic to look at–just trees shaking as the seismic waves roll through–but it is every bit as much of a caldera collapse as something CGI’d in a supervolcano movie.
Only it’s in real life, and happening so slowly that we can watch it in relative safety, while carrying on with our lives as usual nearby. And there hasn’t been one of these otherwise daily occurrences since August 2nd; it may never happen again our lifetime. (Then again, it might–you can’t be sure of anything around Pelee!)
First off, here’s a skiing video, without a single mention of volcanoes. But everything they are travelling over, under, around and through is part of the Laguna del Maule volcano complex on the Chile-Argentina border.
Yes, it’s an active volcano. In fact, until last year it seemed the most likely candidate for the world’s next supereruption.
The lava fountains and human drama in Hawaii’s Lower Puna District are getting all the headlines, but geologists know there is also drama ongoing at the summit, where the volcano’s crater seems to have been slowly collapsing since the lava lake drained.
Hawaiian Volcano Observatory staff were forced to move farther away from the summit area because the many earthquakes there were damaging the building. Now, they have set up a livestream, and it’s fascinating to watch. Basically, the crater walls are slowly crumbling inward, and there is a pile of rocks at the bottom that may be suppressing the explosions — after a period of suppression, of course, there will likely be a big steam blast to relieve pressure, But no one knows if or when that will happen, or what will happen next.
Anyway, here’s the livestream:
For comparison, here’s a video they recorded in March to mark the ten-year anniversary of the lava lake first appearing in the summit crater. Where he’s standing has already collapsed now.
Here is a drone overlight of Halemaumau they did on May 31st. As you can see, the vent where the lava lake used to be has expanded to almost fill the whole crater. And there’s the rock pile down at the bottom, probably supressing, to some extent, the explosions.
You need this background to the recent news that, at Havre Seamount near New Zealand, scientists have found the largest deep-water silicic eruption in history. Some cool videos of eruptions are included, too.
Thanks to plate tectonics, almost three-quarters of Earth’s lava is erupted in the oceans, at mid-ocean ridges, not on the land where we can see it.
These spreading ridges, as they are called, are really a high volcanic mountain range rising from the abyssal depths and running down the middle of just about every ocean on the planet.
Most of that lava and rock is mafic – a word coined from the chemical symbols for magnesium and iron, which enrich this type of magma and make the resulting rock dark.
This runny red stuff usually erupts quietly as pillow lava, but in relatively shallow water, mixing molten rock and good old H2O can be spectacularly explosive.
That is the 1963 Surtsey eruption, off Iceland’s southern coast. This volcano sits in the middle of the Atlantic, but since it’s on a coastal shelf (and therefore atop the Mid-Atlantic Ridge, along with Iceland), ocean depth there is measured in hundreds of feet, not miles.
Even so, scientists would have had a hard time studying the eruption if it hadn’t broken through to the air.
Surtsey is made out of mafic rock. Another type of dramatic volcano comes from silicic magma – it contains a lot of silica instead of magnesium and iron.
Usually you find silicic volcanoes near the coast, as in the High Cascades of the US Pacific Northwest. They form in such places because, offshore, a seafloor plate is sinking down into the depths of the Earth and the continental plate is riding over it.
Of course, it’s hot down there in the mantle. Not only that, seawater is mixed in with the sinking rock – this lowers the melting temperature and causes chemical reactions that, among other things, make the silicic magma very sticky.
Volcanoes form wherever this magma reaches the surface near the trench made by the sinking plate edge.
The eruption may be explosive, as when gases build up a lot of pressure. Without so much gas, it can be nonexplosive but gooey, as in the Mount St. Helens eruption that began in 2004.
Here is a USGS closeup view of how Mount St. Helens rebuilt itself between 2004 and 2008:
Sometimes subduction (one tectonic plate sinking underneath another) happens far from land.
Volcanologists know this, but they haven’t been able to learn much about the resulting silicic volcanoes, since it all happens in deep water, which is technically defined as more than 500 meters, or over a third of a mile, below the surface.
The pressure of water at those depths is enough to prevent Surtsey-like blow-ups, so evidence of these eruptions usually goes unseen.
In 2012, though, volcanologists were able to trace a raft of pumice that had been sighted by satellite – see the image at the top of the page – back to Havre Seamount in the general vicinity of the Kermadec Islands.
That in itself was big news, but now technology has also enabled volcanologists to visit the volcano.
That is what all the fuss is about today!
Here is the original University of Tasmania fly-through used by Scientific American in the above video:
As of this writing, the Smithsonian doesn’t have a picture of Havre for the volcano’s GVP page. That’s going to change soon, thanks to this major volcanological success!
Featured image: Havre’s pumice raft spreads across the sea, NASA.
Sources:
Carey, R.; Adam-Soule, S.; Manga, M.; White, J. D. L.; and others. 2018. The largest deep-ocean silicic volcanic eruption of the past century. Science Advances. 4(1):e1701121.
Jakobsson, S. P.; Thors, K.; Vésteinsson, A. T.; and Ásbjörnsdóttir. 2009. Some aspects of the seafloor morphology at Surtsey volcano: The new multibeam bathymetric survey of 2007. Surtsey Research. 12:9-20.
