[Tagging] Hot springs

John F. Eldredge john at jfeldredge.com
Wed Mar 5 18:58:51 UTC 2014

I don't see anything in that definition that says the heat from within the earth has to be a minimum distance below the surface in order to be classed as geothermal. Volcanism is a subset of geothermal, where the hot material is particularly close to the surface.

-------- Original Message --------
From: "Richard Z." <ricoz.osm at gmail.com>
Sent: March 5, 2014 12:08:26 PM CST
To: "Tag discussion, strategy and related tools" <tagging at openstreetmap.org>
Subject: Re: [Tagging] Hot springs

On Wed, Mar 05, 2014 at 09:24:24AM -0600, John F. Eldredge wrote:
> In what sense is volcanic heat not geothermal?

In some sense you could argue that volcanos are also heated by geothermal
heat but the details are very different.


<<Heat sources

Temperature within the Earth increases with depth. Highly viscous or partially molten rock at temperatures between 650 to 1,200 °C (1,200 to 2,200 °F) is postulated to exist everywhere beneath the Earth's surface at depths of 80 to 100 kilometres (50 to 60 mi)[citation needed], and the temperature at the Earth's inner core/outer core boundary, around 3,500 kilometres (2,200 mi) deep, is estimated to be 5650 ± 600 kelvins.[6][7] The heat content of the Earth is 1031 joules.[1]

    Much of the heat is created by decay of naturally radioactive elements. An estimated 45 to 90 percent of the heat escaping from the Earth originates from radioactive decay of elements mainly located in the mantle.[4][8][9]
    Heat of impact and compression released during the original formation of the Earth by accretion of in-falling meteorites.
    Heat released as abundant heavy metals (iron, nickel, copper) descended to the Earth's core.
    Latent heat released as the liquid outer core crystallizes at the inner core boundary.
    Heat may be generated by tidal force on the Earth as it rotates; since rock cannot flow as readily as water it compresses and distorts, generating heat.
    There is no reputable science to suggest that any significant heat may be created by electromagnetic effects of the magnetic fields involved in Earth's magnetic field, as suggested by some contemporary folk theories.

The radiogenic heat from the decay of 238U and 232Th are now the major contributors to the earth's internal heat budget.
Present-day major heat-producing isotopes[10] Isotope 	Heat release [W/kg isotope] 	Half-life [years] 	Mean mantle concentration [kg isotope/kg mantle]


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John F. Eldredge -- john at jfeldredge.com
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