Why does the boiling point of the water in the geyser change?
As was pointed out above, the temperature at which water boils is determined by the pressure on the outside of the bubbles of water vapor. In a shallow pan, the pressure pushing on the outside of the vapor bubble is pretty much equal to the pressure of the air above the liquid. However, pressure increases as you go deeper into a body of water (most of us have experienced the increase in pressure on our eardrums as we dive to the bottom of a swimming pool). In these cases, the pressure on the vapor bubbles becomes equal to the pressure of the air above the liquid, plus the pressure due to the weight of the water. Since geysers extend thousands of feet down into the earth’s crust, the pressure due to the weight of the water at the bottom of a geyser is very great. This means that the water must be heated to a very high temperature before it will boil. But what would happen if suddenly, the pressure on all of this very hot water were released? That would result in a sudden decrease in the
