question: water to steam at great depths

- I'm looking to solve a dispute between myself and a few others.  A
5-6 mile (or more) deep shaft is dug into the Earth's crust to a point
where the temperature of the surrounding rock is sufficient enough to
boil water (450 F possibly).  Is it possible to turn a mile high
column of water to steam in this shaft or would a horizontal shaft
need to be created (because of head pressure) to be able to turn this
water into steam?  If possible in the column, do you feel the the
steam wold condense before exiting shaft?
- The dispute began over a discussion about volcanic vents in the
deepest parts of the Atlantic.