As mentioned in the previous slide, when
the water begins to be heated by magma, the
temperature increases above the boiling point at which it
would normally boil on Earth’s surface, but it still does
not boil. We will now expand on this topic.
Energy can come in
many forms. In our situation we will only be talking about
energy in the form of heat and how that affects the water’s
temperature and pressure. If you look at the atomic level,
temperature is the average kinetic (motion) energy of the
system you are measuring, and if you add energy to atoms you
cause them to move around faster. To simplify the
explanation of a geyser, we are going to consider the space
where the water is located to be at a constant volume,
meaning that there will be no change in the amount of water
in the geyser.
As we just discussed,
adding energy to our system increases the average kinetic
energy of all the atoms in the geyser. When the temperature
increases the pressure inside of the geyser also increases.
This can be concluded by looking at what causes pressure on
the atomic level. Pressure is actually caused by the
individual atoms and molecules colliding with the inside
wall of the geyser. More collisions cause a higher pressure
and likewise, a lower amount of collisions will cause a
lower pressure. Since the particles are moving faster from
the energy being added by the hot rocks, there are going to
be more collisions with the inside of the geyser chamber,
which causes an increase in the overall pressure. By looking
at the phase diagram you can see an approximated purple line
that shows an estimate of the path the water might take to
becoming steam. This is what causes the geyser to erupt.
Source:
http://www.akitarescueoftulsa.com/carbon-phase-diagram-of-atm/