R_P wrote: Back in the day when I was still active at the site, a guy at volcano cafe crunched a shit-ton of seismic data to see if there was any synchronicity between earthquakes and moon phases. He found none at all. Possibly there is some effect on the mantle but that is way out of my league. Geomorph?
"Bake tectonic plates at 2000 C for 250,000 to 350,000 years until puffed and golden brown, and a toothpick inserted in the center comes out clean." ~manbird
I bake my bread I burn my oil I bend to the burning soil
A big driver of subduction (and plate motion) is derived from density differences of oceanic plates. Older ones are more dense than young ones and tend to sink into the asthenosphere. That's the simple model. The basic convection model doesn't completely answer the question.
"Bake tectonic plates at 2000 C for 250,000 to 350,000 years until puffed and golden brown, and a toothpick inserted in the center comes out clean."
So the convection is caused by gravitational forces?
A big driver of subduction (and plate motion) is derived from density differences of oceanic plates. Older ones are more dense than young ones and tend to sink into the asthenosphere. That's the simple model. The basic convection model doesn't completely answer the question.
no evidence of that that I know of. magnetic reversals are very common and there doesn't seem to be any correlation to higher eruption rates in the geological record. While we are at it, there is no correlation to phases of the moon either. The biggest driver of volcanism remains convection of the mantle shunting the (very thin) crust about. It's amazing that an area the size of the Pacific is, in geological time, actually very young and being constantly rejuvenated on the Eastern Pacific Rise and consumed at the subduction zones of the western Pacific.
Convection in the mantle also accounts for hot spots like Hawaii or Iceland.
So the convection is caused by gravitational forces?
no evidence of that that I know of. magnetic reversals are very common and there doesn't seem to be any correlation to higher eruption rates in the geological record. While we are at it, there is no correlation to phases of the moon either. The biggest driver of volcanism remains convection of the mantle shunting the (very thin) crust about. It's amazing that an area the size of the Pacific is, in geological time, actually very young and being constantly rejuvenated on the Eastern Pacific Rise and consumed at the subduction zones of the western Pacific.
Convection in the mantle also accounts for hot spots like Hawaii or Iceland.
At first sight this seems like an extremely unusual eruption. Fast, furious and with little juvenile magma. This got everyone scratching their heads because the received wisdom was that the bigger explosive eruptions involved the release of a lot of gas-rich magma in ashy eruptions that took many hours to days to peak (think sustained eruption column like Pinatubo).
This eruption, by contrast, was almost instantaneous, a sudden bang (four or five in fact) with activity peaking within half an hour and seemed to be mostly steam-driven, not magma driven (ignoring for the moment the fact that Hunga Tonga was still in the middle of a long and sustained eruptive episode and had ramped up considerably recently).
Now, steam-driven eruptions are not unusual at geothermal areas around the globe, involving little craters getting blasted out without warning. The other kind of steam-driven eruption is referred to as Surtseyan and is powered by hot magma interacting with water to create the classic sight of rooster tails. It's all kind of dramatic, but actually pretty docile, provided you keep a healthy distance.
This was what Hunga Tonga had been doing intermittently for a couple of years before it suddenly went off, big time. And by big time, I mean big time. Like many orders of magnitude bigger. The blast is comparable to the biggest nuclear device ever exploded, the Tsar bomb. That is some serious power.
A lot of people had been assuming we would always have some kind of warning before a major eruption occurs. Turns out, we don't, necessarily. But something else strikes me: maybe these explosions are not that uncommon. I can think of four real humdingers in the Holocene off the top of my head:
Santorini
Taupo (Hatepe)
Krakatoa
and now Hunga Tonga
all of which bear the same hallmarks of a sudden massive explosion, almost certainly steam-driven or at least initiated by a phreatic blast. Four within 4000 years is actually very frequent on a geological timescale. The common features of these eruptions seem to be volcanos erupting through a body of water, starting with a sustained eruption till some kind of tipping point is reached when the groundwater flashes to steam and the whole thing goes sky-high.
Tread carefully out there.
I have a question which lends itself to a simple theory I suppose. Is the changing position of magnetic north relative to the equator producing an extra change and crunch of the geologic plates and all the increase in activity? The science of it all just seems so vast in scale.
At first sight this seems like an extremely unusual eruption. Fast, furious and with little juvenile magma. This got everyone scratching their heads because the received wisdom was that the bigger explosive eruptions involved the release of a lot of gas-rich magma in ashy eruptions that took many hours to days to peak (think sustained eruption column like Pinatubo).
This eruption, by contrast, was almost instantaneous, a sudden bang (four or five in fact) with activity peaking within half an hour and seemed to be mostly steam-driven, not magma driven (ignoring for the moment the fact that Hunga Tonga was still in the middle of a long and sustained eruptive episode and had ramped up considerably recently).
Now, steam-driven eruptions are not unusual at geothermal areas around the globe, involving little craters getting blasted out without warning. The other kind of steam-driven eruption is referred to as Surtseyan and is powered by hot magma interacting with water to create the classic sight of rooster tails. It's all kind of dramatic, but actually pretty docile, provided you keep a healthy distance.
This was what Hunga Tonga had been doing intermittently for a couple of years before it suddenly went off, big time. And by big time, I mean big time. Like many orders of magnitude bigger. The blast is comparable to the biggest nuclear device ever exploded, the Tsar bomb. That is some serious power.
A lot of people had been assuming we would always have some kind of warning before a major eruption occurs. Turns out, we don't, necessarily. But something else strikes me: maybe these explosions are not that uncommon. I can think of four real humdingers in the Holocene off the top of my head:
Santorini
Taupo (Hatepe)
Krakatoa
and now Hunga Tonga
all of which bear the same hallmarks of a sudden massive explosion, almost certainly steam-driven or at least initiated by a phreatic blast. Four within 4000 years is actually very frequent on a geological timescale. The common features of these eruptions seem to be volcanos erupting through a body of water, starting with a sustained eruption till some kind of tipping point is reached when the groundwater flashes to steam and the whole thing goes sky-high.
Astonishingly loud bang, that one. However, doesn't seem to be a lot of juvenile material but was mostly a steam-driven explosion. Pretty big one though! This might not be the last one of this episode either. Hope none of the low-lying islands to the North East suffered any casualties. No news yet. Apparently two died in Peru and I heard a report from Chile that two died in the tsunami there.
this beast looks like it is ramping up for another eruption. In contrast to La Palma or Iceland, this one actually is scary with an unholy combination of high magma output (and a very recent dike intrusion), loads of water to make it go phreatic and a high population surrounding it.
this beast looks like it is ramping up for another eruption. In contrast to La Palma or Iceland, this one actually is scary with an unholy combination of high magma output (and a very recent dike intrusion), loads of water to make it go phreatic and a high population surrounding it.
bit misleading... they mean the most powerful eruption on that particular island in half a century. There have been a lot of far more powerful eruptions elsewhere around the globe. This one is actually tiny but very typical for the island.
