# How do geysers work?

I'm wondering how geysers do a spontaneous explosion of water and heated vapor instead of a more continuous, homogeneous in time phenomena, such as constant boiling. I don't understand the mechanism that makes geysers explode a certain amount of time the last time they erupted. Please explain me.

I understand that the energy of the eruption comes from heat, which ultimately comes from magma deep in the earth, or from heated water in contact with that magma. the thing I don't understand is this: let's suppose the geyser chamber starts to fill with cold water, and starts to heat. I don't see why it doesn't boil like in a pot, that is gradually and slowly.

I've seen this video, and I don't understand why suddenly when the bubble pushes out water out of the chamber, that makes a pressure drop inducing vaporization in all the chamber.

Another doubt about the video I linked is why, after mass vaporization, there is a eruption. I think that changing from liquid to gas shouldn't suddenly increase the pressure so much, why it should?

Suppose the chamber is a vertical cylinder of area $A$. The pressure at the bottom is $W/A$ where $W$ is the weight of the water. If some water spills the pressure at the bottom is less.