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Re: deep water = less ejecta?
On Jan 27, 2008, at 1:50 PM, don ohmes wrote:
Not qualitatively, according to my understanding; the heat of the
vapor obviously dissipates quickly relative to liquid due in part to
the many point sources involved. Also as the the vapor condenses it
extracts heat from the atmosphere.
True. The specific heat capacity of water vapor is still quite high,
though. It much lower than that of liquid water (assuming standard
pressure and temperature) but the heat capacity of water vapor is
greater than, for example, solid silicious clay. Your point about
point sources for dissipation is well taken; this applies to both the
water vapor and the vaporized rock, however.
A jet of steam is devastating at close range, but cools quickly,
whereas a jet of liquid water (or molten rock) will hold it's heat
True, but this is largely because of the mass differences: a jet of
liquid water will usually have more mass than a jet of steam. If the
mass of the hypothetical jets of material are all the same, then the
liquid water would hold the energy the longest, followed by the water
vapor. The particulate/vaporized rock would probably cool off the
most quickly, though I say this with some hesitation as I do not have
heat capacity data for molten substrates handy. We should also keep
in mind that the superheated ejecta would have higher heat capacity
than at standard temperature; water vapor at 1000 K, for example, has
a heat capacity of 2.288 kJ/kgK (compared to 1.954 kJ/kgK at 500 K).
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205