> On Sep 26, 8:58 pm, "Sea Wasp (Ryk E. Spoor)"
> <seaw...@sgeinc.invalid.com> wrote:
>> On 9/26/12 10:45 PM, n...@bid.nes wrote:
>>> OK, so why are you concerned with the high-frequency dielectric
>>> properties of exotic benthic ices?
>> Looking for cool stuff to exploit -- will natural processes cause it to
>> build up charge and electrocute everything above it? Will it transmit
>> radio waves naturally? I have no idea what the stuff does, but since the
>> characteristic of the ice was mentioned in my references I figured I'd
>> ask to see if there were some likely (or not so likely but believable)
>> consequences of those ices' characteristics.
> I got nothing for Debye relaxation, but did you know that water ices
> are proton conductors and can be magnetized?
> "Ice VI and Ice VII are known as the self-clathrate forms because
> their structure is composed of interpenetrating lattices with
> tetrahedral bonds." (No other ices have this characteristic.)
> and goes on to discuss modeling their magnetizability.
> Suppose there's sufficient irregularly-distributed stuff [element,
> compound, whatever] on your world to dope benthic ice at a particular
> stage in transition between VI and VII so that it becomes strongly
> ferromagnetic (maybe by linking the disordered separate latices so all
> the proton spins can align?), strongly enough to produce a noticeable
> (/usable) field wherever your drama occurs; surface or the deeps. You
> would probably get multiple magnetic poles. It occurs to me that
> quakes would strongly alter the magnetic field by moving the critical
> pressure up or down (or sideways) through ices with the proper dopant
> concentration, making navigation more "interesting" for all involved.
> You could get auroras at all latitudes, moving with the field
> changes...
> What to use as a dopant? I don't know. Doc Smith got away with
> claiming that a little Rhenium made a super-strong alloy (Leybyrdite)
> at least partly because nobody could gather enough Rhenium to call BS
> on him. Pick something fairly exotic.
On Thu, 27 Sep 2012 17:23:13 +0000, Michael Stemper wrote:
> In article <acid54F26s...@mid.dfncis.de>, Jens Kleimann
> <yattering_nos...@web.de> writes:
>>What about icebergs, or large chunks of sea ice? Floating by definition,
>>the (potentital) problem being that they don't last all that long. Or
>>permanently frozen polar caps. Whould these count? And, more
>>interestingly, whould a floating ice cap on an all-water planet stay at
>>the pole despite it not being connected to solid bedrock below?
> I wouldn't think there'd be a problem. One of our polar ice caps is not
> connected to solid bedrock below, but it seems to stay in place.
But, if I remember my geography right, the arctic ice cap is conected to the continents on it's side.
I believe a polar ice cap on an all-water planet would stay on the pole, provided there are no sudden movements equatorwise. The ice that composes said cap, however, would not stay on the pole.
The polar ice cap would be in a steady state with reguard to the surrounding ocean. If it is moving in a certain direction, the ice on the leading edge would melt, but it would be replaced by newly forming ice on the trailing edge of the ice cap. A section of the ice cap, however would eventualy melt as it moves from the trailing edge to the leading edge. Any city build on this section of ice would also eventually sink.
In the event of a sudden movement, where the whole ice cap moves equatorward, it would melt whole, but a new ice cap would form on the vacant pole.
So, over geological time frames, you can expect there to always be an ice cap. Just don't bank on building a permanent settlement there.
On Sep 27, 2:21 pm, Aleksandar Kuktin <akuk...@gmail.com> wrote:
> Hello group!
> The polar ice cap would be in a steady state with reguard to the
> surrounding ocean. If it is moving in a certain direction, the ice on the
> leading edge would melt, but it would be replaced by newly forming ice on
> the trailing edge of the ice cap. A section of the ice cap, however would
> eventualy melt as it moves from the trailing edge to the leading edge.
> Any city build on this section of ice would also eventually sink.
This is to some extent true of our arctic ice cap. While, even during
the summer it extends to the north coasts of Greenland and the
northern
Canadian islands, there is substantial drift. Enough drift, that
Nansen's expedition in the Fram traveled a substantial distance from
the New Siberian Islands to Spitzbergen, locked in the pack ice.
Perhaps debye relaxation-prone materials can affect the propagation of electromagnetic waves.
Now, I don't know enough physics/mathematics to tell if a layer of ice-VI would atenuate or help propagate EM waves (especially with comparion to liquid water), but I reckon it would do one of the two.
>>> :: You can certainly get a world with liquid water that has great depth
>>> :: -- many miles. But (assuming roughly earth-normal gravity) at about
>>> :: 60 miles or so, at temperatures around what we consider normal, it'll
>>> :: start to turn to Ice VI, later to Ice VII and possibly others
>>> :: depending on temperature and exact pressure and so on. (see a phase
>>> :: diagram of water for exact numbers and such)
>>> : JRStern <JRSt...@foobar.invalid>
>>> : What is the normal temperature, on Earth, at 60 miles?
>>> I note that since water convects much faster than rock,
>>> comparing temperatures 60 km depth in rock to 60 km depth in water
>>> is quite like comparing apples to bicycles.
>> Yeah but you've got to start somewhere.
>> SW said "at temperatures around what we consider normal", I suppose
>> meaning 25c. Problem is that at first approximation, temperature on
>> Earth in the mantle goes up about 25c per kilometer, per
>> Google/Wikipedia. Giving us roughly 2500c 60 miles down. May impact
>> his Ice VI scenario.
> But in the oceans, it gets COLDER the lower you go. To a minimum of >slightly above freezing for the particular concentration of salt. I.e., >if you go down a kilometer in the Earth your temperature goes up by 25c, >if you go down a kilometer in the ocean you may find your temperature >goes DOWN by 25c.
Well, that is something. Of course it doesn't keep on getting colder
since it's still liquid. How IS it that it gets colder, when on land
it does not, that nasty convection? If so it has also managed to
continue to cool the ocean floor, which we assume would also be
warmer, 35,000 feet down. Interesting question, actually.
> Cold water sinks... but ice floats, usually. The >density of Ice VI is greater than that of standard water; not sure if >it's greater than that of water at that depth. Have to check. Water >doesn't compress MUCH, but it will compress.
>> OTOH, following your lead, the entire planet may cool much faster with
>> that much water. OTOOH, if Ice XXX does manage to form, it won't be
>> convecting much faster than stone. Or will it?
>> “Europa is about the size of our own moon,” Hand explains. “Its vast
>> ocean is likely more than 60 miles deep (Earth’s ocean depths reach
>> only about seven miles). That means Europa may harbor two to three
>> times the volume of all liquid water on Earth.”
> That's because Europa has roughly 1/8th Earth Normal gravity, so the >pressure at the bottom of that ocean will only be roughly that of an >Earthly ocean 5 miles deep or so -- which being a little over 26,000 >feet is considerably less than the deepest our oceans actually get here >(36,000 feet or nearly two miles deeper).
True, just that it actually occurs, and even locally, and possibly to
greater depths.
I should have mentioned the lower gravity as well as the radioactives,
the whole planetary density issue. Suppose it also matters what's on
top, for all we know Jupiter has oceans of liquid water a hundred
miles deep, with immense atmospheric pressure above helping with the
liquidity.
> On Thu, 27 Sep 2012 11:10:43 -0400, "Sea Wasp (Ryk E. Spoor)"
> <seaw...@sgeinc.invalid.com> wrote:
>> On 9/27/12 10:44 AM, JRStern wrote:
>>> On Tue, 25 Sep 2012 20:28:25 GMT, thro...@sheol.org (Wayne Throop)
>>> wrote:
>>>> :: You can certainly get a world with liquid water that has great depth
>>>> :: -- many miles. But (assuming roughly earth-normal gravity) at about
>>>> :: 60 miles or so, at temperatures around what we consider normal, it'll
>>>> :: start to turn to Ice VI, later to Ice VII and possibly others
>>>> :: depending on temperature and exact pressure and so on. (see a phase
>>>> :: diagram of water for exact numbers and such)
>>>> : JRStern <JRSt...@foobar.invalid>
>>>> : What is the normal temperature, on Earth, at 60 miles?
>>>> I note that since water convects much faster than rock,
>>>> comparing temperatures 60 km depth in rock to 60 km depth in water
>>>> is quite like comparing apples to bicycles.
>>> Yeah but you've got to start somewhere.
>>> SW said "at temperatures around what we consider normal", I suppose
>>> meaning 25c. Problem is that at first approximation, temperature on
>>> Earth in the mantle goes up about 25c per kilometer, per
>>> Google/Wikipedia. Giving us roughly 2500c 60 miles down. May impact
>>> his Ice VI scenario.
>> But in the oceans, it gets COLDER the lower you go. To a minimum of
>> slightly above freezing for the particular concentration of salt. I.e.,
>> if you go down a kilometer in the Earth your temperature goes up by 25c,
>> if you go down a kilometer in the ocean you may find your temperature
>> goes DOWN by 25c.
> Well, that is something. Of course it doesn't keep on getting colder
> since it's still liquid. How IS it that it gets colder, when on land
> it does not, that nasty convection?
Yep. Cold water sinks, hot rises. Which is why you get hotter as you go down in land -- you're at the TOP of the mantle, just getting through that very, very thin, cooled crust at the top.
Because of this, I would expect the oceans to be cold at the bottom even with very deep oceans, until they solidified under pressure... and then other factors come into play.
> >>>> :: You can certainly get a world with liquid water that has great depth
> >>>> :: -- many miles. But (assuming roughly earth-normal gravity) at about
> >>>> :: 60 miles or so, at temperatures around what we consider normal, it'll
> >>>> :: start to turn to Ice VI, later to Ice VII and possibly others
> >>>> :: depending on temperature and exact pressure and so on. (see a phase
> >>>> :: diagram of water for exact numbers and such)
> >>>> : JRStern <JRSt...@foobar.invalid>
> >>>> : What is the normal temperature, on Earth, at 60 miles?
> >>>> I note that since water convects much faster than rock,
> >>>> comparing temperatures 60 km depth in rock to 60 km depth in water
> >>>> is quite like comparing apples to bicycles.
> >>> Yeah but you've got to start somewhere.
> >>> SW said "at temperatures around what we consider normal", I suppose
> >>> meaning 25c. Problem is that at first approximation, temperature on
> >>> Earth in the mantle goes up about 25c per kilometer, per
> >>> Google/Wikipedia. Giving us roughly 2500c 60 miles down. May impact
> >>> his Ice VI scenario.
> >> But in the oceans, it gets COLDER the lower you go. To a minimum of
> >> slightly above freezing for the particular concentration of salt. I.e.,
> >> if you go down a kilometer in the Earth your temperature goes up by 25c,
> >> if you go down a kilometer in the ocean you may find your temperature
> >> goes DOWN by 25c.
> > Well, that is something. Of course it doesn't keep on getting colder
> > since it's still liquid. How IS it that it gets colder, when on land
> > it does not, that nasty convection?
> Yep. Cold water sinks, hot rises. Which is why you get hotter as you go
> down in land -- you're at the TOP of the mantle, just getting through
> that very, very thin, cooled crust at the top.
> Because of this, I would expect the oceans to be cold at the bottom
> even with very deep oceans, until they solidified under pressure... and
> then other factors come into play.
> Oh, this is gonna be FUN.
Assuming stratification does not take place, the deeper the ocean/
smaller the world, the more effective the cooling should be, since the
area of the ocean surface (where it radiates heat) is larger than the
area of the underlying solid planet.
Think about life forms which play with the phase table for biological
reasons; for example, one which has chamber where water can be changed
from Ice III to liquid to lower density, perhaps by adding or removing
antifreeze compounds to the chamber, thus varying the creature's
buoyancy. Or using highly pure ice to form skeletons, while the rest
of its body and the surrounding ocean remains fluid due to salt
content.
On Thu, 27 Sep 2012 13:59:27 -0700, Cryptoengineer wrote:
> [snip]
> Or using highly pure ice to form skeletons, while the rest of
> its body and the surrounding ocean remains fluid due to salt content.
> pt
My brain just experienced a segmentation fault and crashed.
On Sep 27, 5:26 pm, Aleksandar Kuktin <akuk...@gmail.com> wrote:
> On Thu, 27 Sep 2012 13:59:27 -0700, Cryptoengineer wrote:
> > [snip]
> > Or using highly pure ice to form skeletons, while the rest of
> > its body and the surrounding ocean remains fluid due to salt content.
> > pt
> My brain just experienced a segmentation fault and crashed.
Not quite the same, but there are Antarctic fish that live in sea
water below 0C by producing antifreeze compounds in their bodies.
The physical properties of non-standard ice crystal habits at the
extreme pressures SW envisages may be quite different than the brittle
stuff we're used to.
<seaw...@sgeinc.invalid.com> wrote:
>>> But in the oceans, it gets COLDER the lower you go. To a minimum of
>>> slightly above freezing for the particular concentration of salt. I.e.,
>>> if you go down a kilometer in the Earth your temperature goes up by 25c,
>>> if you go down a kilometer in the ocean you may find your temperature
>>> goes DOWN by 25c.
>> Well, that is something. Of course it doesn't keep on getting colder
>> since it's still liquid. How IS it that it gets colder, when on land
>> it does not, that nasty convection?
> Yep. Cold water sinks, hot rises. Which is why you get hotter as you go >down in land -- you're at the TOP of the mantle, just getting through >that very, very thin, cooled crust at the top.
> Because of this, I would expect the oceans to be cold at the bottom >even with very deep oceans, until they solidified under pressure... and >then other factors come into play.
> Oh, this is gonna be FUN.
But then, just noodling, the oceans have been semi-actively cooling
3/4 of the Earth's crust for the past billions of years. And must
continue to do so today. Certainly including where volcanoes and
vents spew heat directly. Does that slowly affect even plate
tectonics, or is the crust just so thin it really doesn't much matter?
> On Thu, 27 Sep 2012 16:36:41 -0400, "Sea Wasp (Ryk E. Spoor)"
> <seaw...@sgeinc.invalid.com> wrote:
>>>> But in the oceans, it gets COLDER the lower you go. To a minimum of
>>>> slightly above freezing for the particular concentration of salt. I.e.,
>>>> if you go down a kilometer in the Earth your temperature goes up by 25c,
>>>> if you go down a kilometer in the ocean you may find your temperature
>>>> goes DOWN by 25c.
>>> Well, that is something. Of course it doesn't keep on getting colder
>>> since it's still liquid. How IS it that it gets colder, when on land
>>> it does not, that nasty convection?
>> Yep. Cold water sinks, hot rises. Which is why you get hotter as you go
>> down in land -- you're at the TOP of the mantle, just getting through
>> that very, very thin, cooled crust at the top.
>> Because of this, I would expect the oceans to be cold at the bottom
>> even with very deep oceans, until they solidified under pressure... and
>> then other factors come into play.
>> Oh, this is gonna be FUN.
> But then, just noodling, the oceans have been semi-actively cooling
> 3/4 of the Earth's crust for the past billions of years. And must
> continue to do so today. Certainly including where volcanoes and
> vents spew heat directly. Does that slowly affect even plate
> tectonics, or is the crust just so thin it really doesn't much matter?
The cooling is significant only on VERY long timescales, I think. The planet in question is quite geologically active.
:: But then, just noodling, the oceans have been semi-actively cooling
:: 3/4 of the Earth's crust for the past billions of years. And must
:: continue to do so today. Certainly including where volcanoes and
:: vents spew heat directly. Does that slowly affect even plate
:: tectonics, or is the crust just so thin it really doesn't much
:: matter?
More that it is so thick it doesn't matter (depending on
which things are in the set of things-that-might-matter-in-this-context).
: "Sea Wasp (Ryk E. Spoor)" <seaw...@sgeinc.invalid.com>
: The cooling is significant only on VERY long timescales, I think. : The planet in question is quite geologically active.
That might make a difference. On earth, given the size of the plates
and any plausible rate of sea-floor spreading, the bottleneck in heat
loss is going to be conductivity through mumble kilometers of crust.
Since the crust is not liquid, it doesn't convect. Compare to volcanic
lava fields; the surface crusts over, and then the rock underneath can
remain liquid for quite a while. And that's without any radioactive
elements decaying in siginficant amounts, and with only a few centimeters
thickness of solid overlaying.
So. The earth as a whole is much like that. If you have something
over the crust that's convective, the crust will bottleneck the heat
from the underlying magma, and it'll have vaguely (give or take a couple
hundred degrees) the same temperature as we've got either at the air-rock
interface, or at the water-rock interface, here on earth.
Now, if the planet in question is very geologically active, as in,
has incredibly fast tectonic motions, and sea floor spreading in some
sort of fractal pattern so it can have actual magma escaping all over
the place instead of in a single thin line... well... it'd be very
different. In fact, it'd be so different it'd be difficult to say
what all the side effects of that would be.
I recall a 1970s Analog short story about a planet where the tectonic
plates were about the size of large islands, and moved... very VERY
fast indeed. Some of them had steering mechanisms of some sort put on
them, etc, etc. I have no idea how plausible that would be.
Not very, I vaguely expect.
On Thu, 27 Sep 2012 20:10:00 -0400, "Sea Wasp (Ryk E. Spoor)"
<seaw...@sgeinc.invalid.com> wrote:
>> But then, just noodling, the oceans have been semi-actively cooling
>> 3/4 of the Earth's crust for the past billions of years. And must
>> continue to do so today. Certainly including where volcanoes and
>> vents spew heat directly. Does that slowly affect even plate
>> tectonics, or is the crust just so thin it really doesn't much matter?
> The cooling is significant only on VERY long timescales, I think. The >planet in question is quite geologically active.
Sounds tricky.
What is the temperature even 1km under the bottom of the Marianas
Trench, or under the Antarctic sea bed, or wherever the coldest water
is now. Under a 100km deep ocean, with the ground temperature
otherwise over 2000c, you're going to have to have a lot of convection
to keep that water near freezing, and ice forming and killing the
convection, would seem likely to melt again soon. Kind of like snow
in Washington DC.
: JRStern <JRSt...@foobar.invalid>
: What is the temperature even 1km under the bottom of the Marianas
: Trench, or under the Antarctic sea bed, or wherever the coldest water
: is now. Under a 100km deep ocean, with the ground temperature
: otherwise over 2000c, you're going to have to have a lot of convection
: to keep that water near freezing, and ice forming and killing the
: convection, would seem likely to melt again soon. Kind of like snow
: in Washington DC.
Why would ice formation kill the convection? Ice is lighter than water,
so it wouldn't stick down there stably; it'd tend to break off and
float up. Hm. Maybe you mean some of the exotic ices are denser
than water, and might insulate as well or better than rock... in which
case, no more than a kilometer or so of ice could coat the sea floor.
Because then heat would build up under it, and destabilize it.
At least, over a megayear or less.
I also think you are vastly overestimating how much heat is pouring out
from the earth, or even something much more active than earth. Take earth
as an example, on average over the surface, it's only 0.075 watts / m^2.
True, at seafloor spreading sites, it's much higher than average, but at
subduction zones, I doubt it's that much higher than the average. If you
pile enough rock on top of something, it'll insulate it remarkably well.
I'm not at all sure where the "ground temperature otherwise over 2000c"
comes from. Seems very unlikely. Sure, you could have that if there
were something insulating the surface... but air doesn't insulate,
nor does water, nor does vacuum (remember, you have 75 milliwatts per
square meter... look at the black body equilibrium temperature for that.
I'm pretty sure it's not 2000c; I mean, even without running the numbers,
think of putting a 75 mW resistive heater on each square meter of the
moon's surface). I don't think it'll get very hot.
So. Like I said. Not sure (nor is it at all clear) where the "otherwise
2000c" comes from. Under what circumstance would it be 2000c? The only
one that comes to mind is if it had several kilometers of rock on top.
Gas, liquid, or vacuum wouldn't do it. And since the context here is
at the top of any solid rock layers, it can't have rock over it.
Nor anything that melts significantly before 2000c.
On Thu, 27 Sep 2012 16:36:41 -0400, "Sea Wasp (Ryk E. Spoor)"
<seaw...@sgeinc.invalid.com> wrote:
>> Well, that is something. Of course it doesn't keep on getting colder
>> since it's still liquid. How IS it that it gets colder, when on land
>> it does not, that nasty convection?
> Yep. Cold water sinks, hot rises. Which is why you get hotter as you go >down in land -- you're at the TOP of the mantle, just getting through >that very, very thin, cooled crust at the top.
> Because of this, I would expect the oceans to be cold at the bottom >even with very deep oceans, until they solidified under pressure... and >then other factors come into play.
> Oh, this is gonna be FUN.
Depending on how cold it is. When water gets below 4 degrees C, it
expands. That is why ice floats. And it's why the arctic has so
much more fish than the tropics, as cold water at the bottom goes to
the top, bringing up nutriments as it goes.
-- "In no part of the constitution is more wisdom to be found,
than in the clause which confides the question of war or peace to the legislature, and not to the executive department."
> On 26.09.2012 19:40, Andrew Plotkin wrote:
>> In rec.arts.sf.written, Wayne Throop <thro...@sheol.org> wrote:
>>> The islands could be dynamically supported by mantle plumes.
>>> Or the tectonics could be otherwise very non-earthlike.
>> Floating islands.
>> Not that I have any idea how to produce *them* on a deep-ocean world.
>> I guess you start by figuring out a plausible mechanism for a
>> twenty-mile-high convection cycle -- get minerals and nutrients up
>> from the sea-floor to the lighted zone -- and then invent big, big
>> algae. Let floating seaweed mat up and "petrify", or dry out anyhow.
>> Maybe a population of microorganisms that like to cling to the roots
>> and bubble.
> What about icebergs, or large chunks of sea ice? Floating by definition, the (potentital) problem being that they don't last all that long. Or permanently frozen polar caps. Whould these count? And, more interestingly, whould a floating ice cap on an all-water planet stay at the pole despite it not being connected to solid bedrock below?
My personal first thought is that you'd always have ice at the poles, it just would always be the _same_ ice.
> In article <acid54F26s...@mid.dfncis.de>, Jens Kleimann <yattering_nos...@web.de> writes:
>> On 26.09.2012 19:40, Andrew Plotkin wrote:
>>> In rec.arts.sf.written, Wayne Throop <thro...@sheol.org> wrote:
>>>> The islands could be dynamically supported by mantle plumes.
>>>> Or the tectonics could be otherwise very non-earthlike.
>>> Floating islands.
>>> Not that I have any idea how to produce *them* on a deep-ocean world.
>>> I guess you start by figuring out a plausible mechanism for a
>>> twenty-mile-high convection cycle -- get minerals and nutrients up
>>> from the sea-floor to the lighted zone -- and then invent big, big
>>> algae. Let floating seaweed mat up and "petrify", or dry out anyhow.
>>> Maybe a population of microorganisms that like to cling to the roots
>>> and bubble.
>> What about icebergs, or large chunks of sea ice? Floating by definition, the (potentital) problem being that they don't last all that long. Or permanently frozen polar caps. Whould these count? And, more interestingly, whould a floating ice cap on an all-water planet stay at the pole despite it not being connected to solid bedrock below?
> I wouldn't think there'd be a problem. One of our polar ice caps is not
> connected to solid bedrock below, but it seems to stay in place.
But it is mostly surrounded by land and anchored to that.
>On Wed, 26 Sep 2012 17:46:05 +0000, Wayne Throop wrote:
>> ::: A depth of 20 miles with a few scattered islands peeking out would
>> ::: be feasible. more than that, probably not. I could imagine some
>> ::: mechanisms to provide very occasional super-high mountains, but they
>> ::: wouldn't last for even human timescales, let alone geologic.
>> :: The islands could be dynamically supported by mantle plumes. :: Or
>> the tectonics could be otherwise very non-earthlike.
>> : Andrew Plotkin <erkyr...@eblong.com> : Floating islands.
>> Oooh, cool.
>> : Not that I have any idea how to produce *them* on a deep-ocean world.
>> : I guess you start by figuring out a plausible mechanism for a :
>> twenty-mile-high convection cycle -- get minerals and nutrients up :
>> from the sea-floor to the lighted zone -- and then invent big, big :
>> algae. Let floating seaweed mat up and "petrify", or dry out anyhow. :
>> Maybe a population of microorganisms that like to cling to the roots :
>> and bubble.
>> Giant turtles. Xref "Mysteries of the Arcana" (where it's turtles all
>> the way down,
>> http://mysteriesofthearcana.com/index.php?action=comics&cid=231 And also
>> xref The Last Airbender, and the giant lion-turtle therein. And David
>> Duncan's "West of January", where all the cities are built on turtles.
>Pumice, plus some plant that tends to grow in a network around >collections of pumice? You would get a fairly flat island, but it would >float.
mstem...@walkabout.empros.com (Michael Stemper) wrote:
>In article <acid54F26s...@mid.dfncis.de>, Jens Kleimann <yattering_nos...@web.de> writes:
>>On 26.09.2012 19:40, Andrew Plotkin wrote:
>>> In rec.arts.sf.written, Wayne Throop <thro...@sheol.org> wrote:
>>>> The islands could be dynamically supported by mantle plumes.
>>>> Or the tectonics could be otherwise very non-earthlike.
>>> Floating islands.
>>> Not that I have any idea how to produce *them* on a deep-ocean world.
>>> I guess you start by figuring out a plausible mechanism for a
>>> twenty-mile-high convection cycle -- get minerals and nutrients up
>>> from the sea-floor to the lighted zone -- and then invent big, big
>>> algae. Let floating seaweed mat up and "petrify", or dry out anyhow.
>>> Maybe a population of microorganisms that like to cling to the roots
>>> and bubble.
>>What about icebergs, or large chunks of sea ice? Floating by definition, the (potentital) problem being that they don't last all that long. Or permanently frozen polar caps. Whould these count? And, more interestingly, whould a floating ice cap on an all-water planet stay at the pole despite it not being connected to solid bedrock below?
>I wouldn't think there'd be a problem. One of our polar ice caps is not
>connected to solid bedrock below, but it seems to stay in place.
Up until the last few years, it's been encircled by bedrock.
-- I used to own a mind like a steel trap.
Perhaps if I'd specified a brass one, it
wouldn't have rusted like this.
>I'm not at all sure where the "ground temperature otherwise over 2000c"
Presumed temperature on Earth 60 miles down, might be more like 2500c
per simple number from Wikipedia of 25c/km.
>comes from. Seems very unlikely. Sure, you could have that if there
>were something insulating the surface... but air doesn't insulate,
>nor does water, nor does vacuum (remember, you have 75 milliwatts per
>square meter... look at the black body equilibrium temperature for that.
>I'm pretty sure it's not 2000c; I mean, even without running the numbers,
>think of putting a 75 mW resistive heater on each square meter of the
>moon's surface). I don't think it'll get very hot.
So you argue that the 60 miles (100km) is insignificant, that the
water will convect away a lot more heat than rock anyway, so under
100km of water you have to a first approximation an Earth-like crust
still limiting core radiation to something like 75mw/meter. My
interpretation (if that's what it was) was that it would somehow be
much higher. Perhaps you're right. But still, if you apply even
75mw/meter to the bottom of a solid mass of ice, what happens? I
dunno, but SW might want to figure it out. It might be enough to
throw off his subocean ice, or what do you think?
: JRStern <JRSt...@foobar.invalid>
: Presumed temperature on Earth 60 miles down, might be more like 2500c
: per simple number from Wikipedia of 25c/km.
Right. Under 60 miles of insulating rock. But the example for which
you're saying the temperature will "otherwise" be 2000c is under zero
miles of insulating rock. Do you mean so mething like, "if only there
were 60 miles of insulating rock, which there isn't"?
: So you argue that the 60 miles (100km) is insignificant,
I argued no such thing. I argued that 100km of rock will have different
thermal properties than 100km of water. As is obvious on earth; if water
acted like rock, the temperature in the marianas trench would be >100c,
whereas it's much closer to 4c.
: But still, if you apply even 75mw/meter to the bottom of a solid mass
: of ice, what happens? I dunno, but SW might want to figure it out. : It might be enough to throw off his subocean ice, or what do you
: think?
I agree, it seems unlikely that thick enough sea floor ice would be stable
under 75mW/m^2, since the lack of convection would allow heat to build
up under the ice. Assuming that you don't have the "ice is lighter than
water" issue, because we're talking a layer of Ice-N for some values of N,
then depth in that *ice* could very likely be more like depth in rock than
depth in water. Meaning, the ice layer couldn't be more than a few
kilometers deep at most, before it became unstable, simply because
it would melt at lower temperatures than rock.
But I don't recall he said how deep the ice layer was. Did he?
Destination unknown, as we pull in for some gas
Freshly pasted poster reveals a smile from the past
Elephants and acrobats, lions snakes monkey
Pele speaks "righteous," Sister Zina says "funky"
How bizarre; How bizarre, how bizarre
On Thu, 27 Sep 2012 15:56:01 -0700, JRStern <JRSt...@foobar.invalid>
wrote:
>On Thu, 27 Sep 2012 16:36:41 -0400, "Sea Wasp (Ryk E. Spoor)"
><seaw...@sgeinc.invalid.com> wrote:
[snip]
>> Oh, this is gonna be FUN.
>But then, just noodling, the oceans have been semi-actively cooling
>3/4 of the Earth's crust for the past billions of years. And must
>continue to do so today. Certainly including where volcanoes and
>vents spew heat directly. Does that slowly affect even plate
>tectonics, or is the crust just so thin it really doesn't much matter?
:: But then, just noodling, the oceans have been semi-actively cooling
:: 3/4 of the Earth's crust for the past billions of years. And must
:: continue to do so today. Certainly including where volcanoes and
:: vents spew heat directly. Does that slowly affect even plate
:: tectonics, or is the crust just so thin it really doesn't much
:: matter? Wow a sub-genre of geologic sf.
You mean, sort of like "Planet X", where X = nekkid people?
ANYhoo... I got the idea that the cause of the supercontinent cycle(s)
was heat buildup under landmasses... but I suppose the same could be said
in reverse, it's due to cooling under oceanmasses.
But that has to be oversimplistic, since you still get sea-floor spreading
continuing for megayears, despite by then the hottest bits being in the
middle of a seriously large expanse of ocean. So if you can't trust
an ocean to cool down a mantle plume in a few megayears, who *can*
you trust?
So... probably it's one of those things where the best summary
is "it's complicated".
"I'm an evil villain bent on bringing pain and suffering
to an unsuspecting world... if you can't trust me,
who *can* you trust?"
--- Dark Lord Chuckles, The Silly Piggy
>On 9/27/12 2:12 PM, n...@bid.nes wrote:
>> Suppose there's sufficient irregularly-distributed stuff [element,
>> compound, whatever] on your world to dope benthic ice at a particular
>> stage in transition between VI and VII so that it becomes strongly
>> ferromagnetic (maybe by linking the disordered separate latices so all
>> the proton spins can align?), strongly enough to produce a noticeable
>> (/usable) field wherever your drama occurs; surface or the deeps. You
>> would probably get multiple magnetic poles. It occurs to me that
>> quakes would strongly alter the magnetic field by moving the critical
>> pressure up or down (or sideways) through ices with the proper dopant
>> concentration, making navigation more "interesting" for all involved.
>> You could get auroras at all latitudes, moving with the field
>> changes...
>> What to use as a dopant? I don't know. Doc Smith got away with
>> claiming that a little Rhenium made a super-strong alloy (Leybyrdite)
>> at least partly because nobody could gather enough Rhenium to call BS
>> on him. Pick something fairly exotic.
You're thinking multiple magnetic poles. I'm thinking an ice-incarnated
computing system, forming over aeons a planetary AI...
> Actually, one of his favorites was an osmium-iridium alloy -- both of >them even farther down the charts!
Osmium, Iridium, Platinum is the second-down trio from iron, cobalt, nickel,
right?
Dave
-- \/David DeLaney posting from d...@vic.com "It's not the pot that grows the flower
It's not the clock that slows the hour The definition's plain for anyone to see
Love is all it takes to make a family" - R&P. VISUALIZE HAPPYNET VRbeable<BLINK>
http://www.vic.com/~dbd/ - net.legends FAQ & Magic / I WUV you in all CAPS! --K.
> On Thu, 27 Sep 2012 17:23:13 +0000, Michael Stemper wrote:
>> In article <acid54F26s...@mid.dfncis.de>, Jens Kleimann
>> <yattering_nos...@web.de> writes:
>>> What about icebergs, or large chunks of sea ice? Floating by definition,
>>> the (potentital) problem being that they don't last all that long. Or
>>> permanently frozen polar caps. Whould these count? And, more
>>> interestingly, whould a floating ice cap on an all-water planet stay at
>>> the pole despite it not being connected to solid bedrock below?
>> I wouldn't think there'd be a problem. One of our polar ice caps is not
>> connected to solid bedrock below, but it seems to stay in place.
> But, if I remember my geography right, the arctic ice cap is conected to > the continents on it's side.
> I believe a polar ice cap on an all-water planet would stay on the pole, > provided there are no sudden movements equatorwise. The ice that composes > said cap, however, would not stay on the pole.
> The polar ice cap would be in a steady state with reguard to the > surrounding ocean. If it is moving in a certain direction, the ice on the > leading edge would melt, but it would be replaced by newly forming ice on > the trailing edge of the ice cap. A section of the ice cap, however would > eventualy melt as it moves from the trailing edge to the leading edge. > Any city build on this section of ice would also eventually sink.
> In the event of a sudden movement, where the whole ice cap moves > equatorward, it would melt whole, but a new ice cap would form on the > vacant pole.
> So, over geological time frames, you can expect there to always be an ice > cap. Just don't bank on building a permanent settlement there.
So the current consensus seems to be that a) Earth is not a good example to settle this since the ice layers of both of its poles can only drift slightly because they are frozen to either land masses or bedrock below it, and that b) ice from the poles is likely to gradually drift away equatorwards and melt, while being continuously replenished by newly formed ice at the poles. This indicates that the two crucial numbers to compare would be the rate at which new ice forms vs. the velocity at which it gets carried away. Can one speculate about the magnitude and flow pattern of near-surface ocean circulation on an all-water (but otherwise more or less Earth-like) planet? With a deep and even sea floor, and in the absence of continental flow barriers, I'd expect them to be rather smooth and uniform, but I'm unsure as to how this could be determined more accurately.
Jens.
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