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Echoes of the Ice Age (Pre-History)
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Boreades


In: finity and beyond
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Is 5,000 years ago very useful?

No, it's not. Especially out of context. Please forget I mentioned that.
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Hatty
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In: Berkshire
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aurelius wrote:
The weight of ice bearing down on Antarctica disguises the fact that the 'continent' would be an archipelago of large islands, if brought to the present day surface, though with an extensive continental shelf.

Antarctica, minus the ice, is surprisingly mountainous according to NASA and described on Wiki as having 'the highest average elevation of all the continents'



We've constantly been told that the land is rising in the north and sinking in the south-west due to isostatic rebound (or perhaps a time limit has been fixed for rebounding by now). Are land surfaces in northern Canada and Scandinavia said to be rising too?

P.S. And welcome aboard, Aurelius.
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aurelius



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Hatty wrote:
aurelius wrote:
The weight of ice bearing down on Antarctica disguises the fact that the 'continent' would be an archipelago of large islands, if brought to the present day surface, though with an extensive continental shelf.

Antarctica, minus the ice, is surprisingly mountainous according to NASA and described on Wiki as having 'the highest average elevation of all the continents'



We've constantly been told that the land is rising in the north and sinking in the south-west due to isostatic rebound (or perhaps a time limit has been fixed for rebounding by now). Are land surfaces in northern Canada and Scandinavia said to be rising too?

P.S. And welcome aboard, Aurelius.


Why thank you Hattie. Yes there are 'raised beaches' in Scandinavia, Scotland etc.
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Hatty
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From the images of raised beaches it is clear there were higher sea levels at some stage(s) but it isn't clear that the land has risen.

Is putting quotation marks around raised beaches signalling that the term is in some way inaccurate?
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Boreades


In: finity and beyond
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Is it because everyone can plainly see they are 'raised beaches' with things like sand and seashells, but nobody can agree whether it's because (a) the land has risen or (b) there was a tsunami? There is a third option (c) the sea level has fallen, but I haven't found anyone backing that horse.
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aurelius



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Assuming there have been multiple Ice Ages, not just the current one, then indeed the sea level would have fallen as well as risen over millions of years. However if we can agree the orthodox rock stratigraphy and dating methods then if the raised beaches coincide with the Quaternary Ice Age (again, if you believe this can be reliably dated) it is logical to accept that the raised beaches were cut during a period when the sea level was lower.

As Boreades points out the presence of marine fossils in the uplifted strata would support this.
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aurelius



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Er... I mean cut when the sea levels were higher. There is still lots of ice around captured from the Water Cycle so I guess that's one reason why the sea level hasn't reclaimed those beaches yet - unless other factors are at work keeping that land high.
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aurelius



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Boreades wrote:
Is it because everyone can plainly see they are 'raised beaches' with things like sand and seashells, but nobody can agree whether it's because (a) the land has risen or (b) there was a tsunami? There is a third option (c) the sea level has fallen, but I haven't found anyone backing that horse.


One would expect there to have been many tsunamis in the past, and there is evidence which suggests this. However there are raised beaches all around the Northern Hemisphere (at least), including Canada.

With a tsunami one would expect not just seashells and sand but the remains of any land creatures, maybe trees smashed or drowned by the event.

It is the association of marine fossils with raised beaches that would suggest to me either a change in sea or land level.
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aurelius



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Hatty wrote
Antarctica, minus the ice, is surprisingly mountainous according to NASA and described on Wiki as having 'the highest average elevation of all the continents'

Agree, though only the mountainous areas are above sea level at present so if we simply 'look through' the ice cap what I think we would see is an archipelago of large islands, with a lot of continental shelf under water - until it rebounds.
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Chad


In: Ramsbottom
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simply 'look through' the ice cap

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aurelius



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Nice image, Chad. Where's it from? I worry about attachments in case they send my message to Hell!
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Ishmael


In: Toronto
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aurelius wrote:
Oceanic crust is basaltic. If I understand you correctly Ishmael then one would expect Turkmenistan to have basaltic geology. Does it?


I don't even know what Basaltic is---other than being a monstrous form of vinegar.
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Ishmael


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aurelius wrote:
The angle of tilt of the Earth's axis in respect of the plane of its orbit is supposed to vary from 22.1 to 24.5 degrees to the vertical in a cycle of 41,000 years. With the equatorial bulge caused by centrifugal force, would this be enough to explain the inundation or raising of land masses, Ishmael?


No. We must tilt the Earth 23 degrees or so to submerge the Andes.
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Ishmael


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Chad wrote:
simply 'look through' the ice cap



Clearly an extension of South America, with the spine of the Andes running down the "western side."

In fact, Antarctica is merely the part of South America that has slipped to the south.
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aurelius



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Absolutely, and the broken spine continues up eastern side of the formerly adjacent plate of Australia.
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