Snow, the reason explosions are explosions [from pressure vessels] is that the pressure is suddenly released and the contents if they are flammable burn rapidly on voluminous mixture with air.
The point is the superheated liquid, with all that energy instantaneously changing to gas energy in a very large volume. When very rapid burning also occurs, the combination is a bang heard around the world.
The energy release is measured in umpty megatons.
While there would be some surface activity to start with, that's not necessarily the case. The boiling could start deeper where it's hotter. The pressure relief comes from tidal action [sun and moon alignment during low pressure from air and water]. So, deep down, a bunch of water decides that it is now in gas phase, pushing upwards, using the spare energy from being at 200 degrees [Celsius] or some such, having been kept in liquid phase by the pressure.
The rise pushes water off the top, which lowers the pressure further, causing more conversion to gas phase, which moves more water and pretty soon [like a few seconds - waves don't take long to travel along the surface of a lake] there is quite a column of gas formed, which pops out the surface, removed more load, which propagates the gas formation up and down the column of liquid.
Geysers work like that as do exploding pressure vessels - the pressure is removed which kept the molecules in liquid phase, but suddenly they turn to gas, and burn as they leave the vessel.
It's a bang, not a pretty fountain of lava. The process takes seconds, minutes and perhaps hours rather than days and weeks. Evacuation is a nice idea, but the time to evacuate is now, BEFORE the eruption. Pyroclastic flows are fast - faster than cars can drive down the Waikato river valley. Heading for Rotorua would be problematic with hot pumice raining down.
Yes, looking across lake Taupo towards the mountains is absolutely beautiful on a sunny winters day with clear air, blue sky and green trees and grass. Totally idyllic. It's hard to imagine a stormy winter night with howling westerly driving rain and snow into your teeth but that happens each year. It's harder still to imagine the lake going 20km up into the sky along with cubic kilometres of molten pumice.
But it really is a live caldera. It's a magma based geyser, like Old Faithful, going off regularly, though not quite as precisely timed.
Mqurice |
