Re: deglaciation re: Spin is *NEVER* wrong.

Kent Paul Dolan wrote:
> r norman wrote:

>> The problem statement is: "At the same time the
>> disappearance of ice caps will change the
>> pressures acting on the Earth's crust and set off
>> volcanic eruptions across the globe. " That one
>> strikes me (and others here) as a bit
>> far-fetched. It is known that isostatic rebound
>> after deglaciation, the uplift produced by the
>> release from the heavy weight of the ice cover,
>> can cause earthquakes and volcanic activity in
>> that particular area. There do exist glaciers in
>> numerous alpine locations (meaning high
>> elevation, not specifically the Alps) but whether
>> they are subject to such action is a question.
>> The massive ice fields in Patagonia and Alaska
>> already lie in regions of great tectonic
>> activity, the "ring of fire" so those are
>> vulnerable. In fact the plate boundaries now
>> subject to high volcanic and earthquake activity
>> are spread across the globe -- not randomly but
>> indeed widely spread. That might be what is
>> meant. Or it might just be typical news release
>> hype to gain readership. In any event, the
>> danger is almost certainly restricted to the
>> locations of the ice cover which is definitely
>> not just the arctic and antarctic.

> The idea that the danger would be worldwide seems
> pretty obvious and reasonable to me, just from an
> intuitive grasp of the 3D geometry.

> Let me paint a picture.

> The following is entirely surmise, since I
> can't do the associated math.

> 1) Let's restrict ourself to Antarctica, for
> simplicity.

> 2) The isostatic depression of Antarctica not only
> presses down, but by flattening the local figure
> of the earth, presses sideways too, because the
> circumference of the Antarctic plate must grow to
> hold the same plate surface area in a flatter
> configuration.

> 3) Remove all the ice.

> 4) Sea levels rise everywhere, so weight of water
> on the ocean floor increases, so ocean floors away
> from Antrctica subside, a bit. What effect this
> has, will be ignored here, in favor of the next
> bit.

> 5) Isostatic rebound of Antarctica reduces the
> horizontal pressure it exerts on the plates around
> it, inducing them all to move toward the south
> pole. This motion is transmitted (at the speed of
> sound in rock, which doesn't much matter, because
> "remove all ice" isn't an instantaneous event) to
> surrounding plates. Unfortunately, moving plates
> means earthquakes, and moving plates unusually
> fast, as by a rapid deglaciation of Antarctica,
> probably means unusually large earthquakes.

> 6) The next outermost surrounding plates all get a
> chance to relieve the tension at their borders,
> and that opens gaps at the boundaries or at least
> weakens the crust at the boundaries. In some weak
> places along those boundaries, this will probably
> mean volcanoes.

> 7) That relaxation effect continues to spread from
> plate to plate until it damps out at the opposite
> end of the earth.

The (currently playing here in Tempe AZ as I type
this) National Geographic television series episode
of Naked Science pretty much confirms, with lots of
easily understood experimental examples, the
predictions in the previously referenced paper, that
the global warming deglaciation will lead to
increased vulcanism and stronger and more frequent
earthquakes.

This makes my toy explanation above about the
situation particular to Antarctica a bith more
credible.

As part of the same episode, the point was made that
violent shifts in earth's climate during global
warming episodes can require as little as two
decades to switch climate modes, making the "oh,
I'll be long dead before all this happes" mantra a
bit less comforting.

Dragging things back on topic for talk.origins, a
lot of change to existing environmental niches is
pretty much going to guarantee in advance a period
of rapid evolution and also rapid extinction.

FWIW

xanthian.

.

Relevant Pages

  • deglaciation re: Spin is *NEVER* wrong.
    ... > from the heavy weight of the ice cover, ... In fact the plate ... The isostatic depression of Antarctica not only ... that opens gaps at the boundaries or at least ...
    (talk.origins)
  • Re: deglaciation re: Spin is *NEVER* wrong.
    ...  > from the heavy weight of the ice cover, ... The isostatic depression of Antarctica not only ... circumference of the Antarctic plate must grow to ... weakens the crust at the boundaries. ...
    (talk.origins)
  • Media Hype On Melting Antarctic Ignores Record Ice Growth (Hey Ross: Bite me!)
    ... Media Hype On 'Melting' Antarctic Ignores Record Ice Growth ... ignoring the current record ice growth on Antarctica. ... scientists who study the area. ...
    (sci.anthropology.paleo)
  • Re: Antarctic Glaciers Sloughing Of Ice Has Scientists at a Loss
    ... Antarctic Glaciers' Sloughing Of Ice Has Scientists at a Loss ... Antarctica and their "ice streams" to lose ice to the ocean in recent ... Huge Deposit of Ice Is Gauged at the South Pole of Mars ... blanket the planet in 36 feet of water if they were liquid, ...
    (sci.military.naval)
  • But of Course - Theres Nothing to Worry About - Right ?
    ... Ministers get close look at Antarctic ice threat ... TROLL RESEARCH STATION, Antarctica — A parka-clad band of environment ministers landed in this remote corner of the icy continent on Monday, in the final days of an intense season of climate research, to learn more about how a melting Antarctica may endanger the planet. ... Representatives from more than a dozen nations, including the U.S., China, Britain and Russia, were to rendezvous at a Norwegian research station with American and Norwegian scientists coming in on the last leg of a 1,400-mile, two-month trek over the ice from the South Pole. ... The visiting environment ministers were those of Algeria, Britain, Congo, the Czech Republic, Finland, Norway and Sweden. ...
    (soc.senior.issues)