Bubbling under

Posts on matters volcanic from the Northern mid Atlantic spreading zone and other thoughts about volcanoes.

What makes a volcano erupt?

Sample answers;

From eHow
First Factor
The first factor in an eruption is the buoyancy of the lava. When the rocks melt into lava form, the mass of the molten rock stays the same, but the volume increases by a great deal. This is lava, which is more buoyant than the rock and rises toward the top of the volcano.
Second Factor
Gases within the magma is the second factor. The lava gives off high pressure gases like carbon dioxide and sulphur dioxide. As these gases expand, the lava is pushed toward the top. Increased pressure from the gases pushes the magma even higher, causing and eruption.
Third Factor
An eruption can also be caused by the flow of new magma into an already magma filled volcano. As the new magma enters, pressure is increased, causing the volcano to erupt. Naturally, all these forces happen rapidly with explosive pressures, causing the gases and magma to be thrown for miles around.

There is a similar explanation at Scientific American

These are the classic definitions, but what I want to know is; what drives this process? Can we tell if crustal melt is going to send a whole surge of magma up a fissure out into the habitable biosphere? Before the magma surge would be useful, thus saving lives and not coming as such a big surprise. Downgrading a large eruption from disaster to mere inconvenience.

I've been watching tremor swarm activity in Iceland for just under a year now, and am starting to form some ideas about the eruptive process and how it works.

Iceland is an interesting locale because of the regular seismic 'swarms' you can observe via the Icelandic Met Office's Earthquake web site. These swarms seem to share one thing in common; they resemble the behaviour of boiling liquids. No two bubbles burst in exactly the same place. Like the various swarms under Iceland. A pulse of Magma appeared to shoot up under Langjokull and fill, then drain from, the empty vent system known to exist under the south western corner of the glacier cap. Similar 'pulses' appear to generate swarm activity all across the island at various depths depending upon the vent systems they fill and drain from.

What has me wondering is the process, or processes, that generate these pulses of magma. How deep do they start, and is there any way of monitoring the triggering events. True there is a multitude of surface based monitoring devices, but these generally speaking only give a short term snapshot and have limited success in mapping the processes underlying eruptions.

Considering the disruption and damage large volcanic eruptions can cause, some serious investment in understanding crustal activity might not be such a bad idea. This would involve perhaps having a detector network capable of mapping and displaying major and potentially major events under our feet in real time. Monitoring crustal thinning or thickening which, while we could not possibly hope to influence the process with our current level of technology, but would give people a chance to get the hell out of the way when something does decide to go 'Foom'. Better still, a more accurate assessment of the risk.

Wonder if something could be built that monitors particles like Neutrinos and their oscillation, and by mapping their passage through the Earth beneath our feet provide a better picture of the Earth's core and upper Mantle as it happens. We have the computing power. Perhaps the idea isn't so far fetched as I first thought.