On 12/20/23 08:01, John Harshman wrote:
On 12/20/23 6:54 AM, Trolidan7 wrote:
On 12/19/23 15:15, John Harshman wrote:
On 12/19/23 2:52 PM, Peter Nyikos wrote:
Live Science short video, a bit under 2 minutes
https://www.msn.com/en-us/news/technology/iceland-comes-from-greenland/vi-AA1lE1Fe
The gist of it is a hypothesis [1] that Greenland passed over a hotspot >>>> between 80 and 40 million years ago, and after it emerged, Iceland
was built
above the hotspot, where it stands today.
[1] not identified as such, but treated as a discovery.
Title: Iceland Comes From Greenland?
Scientists learn to better understand the movement of Greenland, as
it was slowly pushed over the hotspot that is now located under
neighboring Iceland.
Nothing stands still over geologic time, and even the biggest land
masses are constantly being reshaped by Earth.
Credit: Goddard Space Flight Center and Dan Gallagher, Jefferson
Beck, Ernie Wrigh
[end of blurb for the video]
A really neat feature is that, while pausing the video, you can
move along the track of the video at your own pace,
and watch the conjectured path that Greenland took during those
forty million years.
The hotspot seems to trace a path from the north end of Greenland to
almost its south end.
Well, you mean that Greenland seems to trace a path over the hot
spot. It seems as if the mid-Atlantic ridge also must move a bit west
in this scenario, so that Greenland's movement is a combination of
its spreading from the ridge and motion of the ridge. I wonder if
Iceland and the ridge will eventually move off the hot spot, leaving
it to sink while the hot spot gives rise to an island chain
resembling Hawaii.
Well you know, what is the motive force that drives plate
tectonics?
Mantle convection and slab pull, as I understand it.
Probably it would involve something on the order of heat
convection from the Earth's core.
Does the term 'mantle plume' refer to any exact model?
If it is unclear exactly what that means then the response
ends up 'we don't know'.
Is Iceland the center of the motive force opening up the
north Atlantic and Arctic oceans? Maybe?
It's at least situated right on the mid-Atlantic ridge. Whether that's
the center of the motive force is open to discussion. Why?
Well this seems to be the subject of the thread.
You know I get the idea that the Galapagos Islands
are at the triple boundary between the three major
plates that were diverging under the Pacific Ocean
for a while and are generally still there.
Maybe about 30 years ago after the meteor from
outer space theory came out I read this one article
from Scientific American where it laid out that Iridium
can come from volcanism and that there may have simply
been an extensive period of volcanism at the K-T
boundary that had nothing to do with a meteor. It
proposed or suggested the idea that increased
volcanism could result from the emergence of convective
events from the Earth's core emerging into the upper
mantle at the boundary of the mantle to the crust.
Do you think it feasible that the hot spot under
Hawaii may have once been at the boundary between
two plates that was causing divergence between them,
but now it is weak enough that it can not effectively
oppose the divergence at the Galapagos Islands, or
do you generally think that the source of movement
may be more diffused over a wider distance under the
plates? That article about 30 years ago seemed to
give a lot of evidence that iridium could come
from volcanism as well as meteors, and that there
was no meteor strike at the KT boundary around
that time.
It also might be true that North America was
diverging from from Eurasia prior to that time,
and increased volcanism from the emergence of
a hot spot migrating from the core to the
upper mantle might not be a viable theory of
why the KT boundary was so abrupt. Then again
who knows.
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