system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the depressurization of Taal Volcano a bad thing?

The local authority in the Philippines says that the ground fissures from quakes are concerning because they suggest there will be an explosive eruption. However, to an ignorant fool like me, depressurization sounds like a good thing. It seems to me if there is less pressure then there would be a less forceful eruption. But it seems like I'm wrong and I would like to learn why.
gpt
Think about what happens when you have a bottle of carbonated water that has been shaken, and you try to open it gently. When the bottle is sealed, the contents is under pressure, and thus stable.

Now you slightly unscrew the cap so that the over pressure can start to equalize. Some of the carbon dioxide dissolved in the liquid will start to escape and form gas bubbles when the pressure drops. Since a gas is much less dense than a liquid, these will quickly rise to the top and escape out through the opening in the cap. However, if the amount of gas that escapes is large enough, the temporary increase in volume will force the liquid all the way up to the cap and, if you're not fast enough in your reactions to screw it back in place, will cause the water to spray out. If you're fast enough, the liquid settles back down, and you can repeat the process until the pressure is equalized to the outside.

In both cases the end result is a completely un-pressurized container of water. But in the first case, you will get sprayed by some of it due to the violent manner of depressurization.

Now imagine the water is molten rock and shit, and the bottle is as large as a mountain, and someone just unscrewed the cap slightly.....

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Edit: Clarified the conversion from dissolved carbon dioxide to gas a bit, to make it a bit more accurate and less hand-wavy.