CometII
Topic Author
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Tsunami Under A Deep Ice Pack

Wed Jul 17, 2013 2:54 pm

Argentina's Seismic Administration reported a 7.3 earthquake near one of their Antarctic bases.

http://tvnz.co.nz/world-news/large-e...thquake-strikes-antarctica-5511544

There were no injuries or damage, but this made me realize, I had never thought about earthquakes in Antarctica, but they obviously happen, since there are volcanoes there too.

What would happen if a very powerful earthquake, say magnitude 9, occurred underneath one of the very deep ice shelves? Would they be broken apart into pieces? Would it be thick enough to not break up, in which case, would then entire ice pack "rise" and come ashore?

Has such an event ever been documented, or even studied in computer simulations? I find it intriguing and a bit scary!
 
Rara
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RE: Tsunami Under A Deep Ice Pack

Wed Jul 17, 2013 3:42 pm

I guess not much would happen at all. Tsunamis aren't really "waves" as such, they're just differences in the water surface which causes water at the shore to swell up and flood inland. I would imagine ice shelves are flexible enough to bend along the ocean surface. Right at the shore the ice would probably well up and the land beneath it may be flooded, but I don't think the ice packs would come ashore.

That's all just guesswork though.
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oly720man
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RE: Tsunami Under A Deep Ice Pack

Wed Jul 17, 2013 4:39 pm

For a tsunami, that will only really be an issue when the sea is shallow and large waves can develop. In deeper water, the rise in water level due to an undersea earthquake may only be a few cm and will have little effect.

http://www.bom.gov.au/tsunami/info/faq.shtml

An earthquake may cause ice to fracture at the junction of land and sea because the land may move suddenly and the sea won't, and this may release more icebergs, perhaps.

Another issue relating to ice and earthquakes is that a lot of ice tends to press down on the land and suppress earthquakes. This is similar to the situation in Iceland with the volcanos having glaciers on top of them and this tends to reduce volcanic activity. A reduction in the amount of ice is like taking the wire off a champagne cork.

From recent reports, there are a number of oddities in Antarctica, for example very deep lakes draining and causing the surface profile to change.

http://www.upi.com/Science_News/2013...ve-buried-lake/UPI-33461372793506/
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AR385
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RE: Tsunami Under A Deep Ice Pack

Thu Jul 18, 2013 5:08 am

Quoting oly720man (Reply 2):
From recent reports, there are a number of oddities in Antarctica, for example very deep lakes draining and causing the surface profile to change.

A little off topic, but adding to that, all the life that inhabits those deep lakes is outstanding too.
 
StarAC17
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RE: Tsunami Under A Deep Ice Pack

Sat Jul 20, 2013 10:13 pm

Quoting Rara (Reply 1):
Tsunamis aren't really "waves" as such, they're just differences in the water surface which causes water at the shore to swell up and flood inland.

   If you were near the epicentre of the 2004 tsunami in the Indian Ocean you probably wouldn't have noticed anything at all.

Quoting oly720man (Reply 2):
For a tsunami, that will only really be an issue when the sea is shallow and large waves can develop. In deeper water, the rise in water level due to an undersea earthquake may only be a few cm and will have little effect.

I would reckon places like Australia, New Zealand, and the southern coasts of Africa and South America could be at risk as tsunamis can travel far.

Quoting oly720man (Reply 2):
Another issue relating to ice and earthquakes is that a lot of ice tends to press down on the land and suppress earthquakes. This is similar to the situation in Iceland with the volcanos having glaciers on top of them and this tends to reduce volcanic activity. A reduction in the amount of ice is like taking the wire off a champagne cork.

Aren't most of the volcanoes in Iceland ones that typically do not erupt explosively (like Mt. St. Helens) but are more like the Hawaiian Island ones. The reason that the 2010 eruption was explosive was that the overlying glaciers increased the magma pressure of Eyjafjallajökull.
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oly720man
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RE: Tsunami Under A Deep Ice Pack

Mon Jul 22, 2013 11:14 am

Quoting StarAC17 (Reply 4):
The reason that the 2010 eruption was explosive was that the overlying glaciers increased the magma pressure of Eyjafjallajökull.

I thought some of the explosiveness was due to water from the glaciers running into the volcano and being converted into steam - and the water content also caused the large ash clouds rather than there just being a magma flow.

Quoting StarAC17 (Reply 4):
I would reckon places like Australia, New Zealand, and the southern coasts of Africa and South America could be at risk as tsunamis can travel far.

Undoubtedly but the I read the OP to be considering the effect of a tsunami on the antarctic ice sheet itself.
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A320ajm
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RE: Tsunami Under A Deep Ice Pack

Tue Jul 23, 2013 9:57 pm

Earthquakes that generally cause tsunamis are generally mega-thrust earthquakes in a marine setting e.g. 2004 Boxing Day Tsunami, 2011 Tohoku Earthquake. I think it's unlikely, if I have understood your post correctly, for an earthquake on the Antarctica shelf to cause a tsunami. This is because the ice in Antarctica is sitting upon a continental mass, not floating upon water. Saying that, a large earthquake could cause an 'ice slip' causing a large block of ice to fall into the sea, subsequently generating a tsunami.

Interestingly, ice quakes occur too - which is ice fracturing in a similar manner to the plates, and these are starting to be recorded more for scientific research.

A320ajm
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