Comments on: The Rise and Fall of Sea Levels and Civilisations. http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/ An Evolving Exploration into the Head, Heart and Hands of Energy Descent Mon, 13 Feb 2012 00:35:27 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Nadia Hillman http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52508 Nadia Hillman Thu, 27 Sep 2007 22:15:54 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52508 <p>Is Totnes not destined to slide into the sea anytime soon? Only I think I might like to retire there you see!</p> Is Totnes not destined to slide into the sea anytime soon? Only I think I might like to retire there you see!

]]> By: ME2 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52471 ME2 Mon, 24 Sep 2007 09:20:41 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52471 <p>Very entertaining story and ensuing discussion.</p> <p>I live on the Queen Charlotte Islands in BC, Canada, an area which has also experienced the effects of glacial depression and rebound. And as the Pacific Plate slides alongside us, we are slowly dragged about two inches a year towards Alaska !</p> Very entertaining story and ensuing discussion.

I live on the Queen Charlotte Islands in BC, Canada, an area which has also experienced the effects of glacial depression and rebound. And as the Pacific Plate slides alongside us, we are slowly dragged about two inches a year towards Alaska !

]]> By: D http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52277 D Thu, 06 Sep 2007 10:24:01 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52277 <p>An interesting piece, stories of lost cities and lands taken by the sea such as Lyonnesse, Cantref Gwaelod and Atlantis never fail to excite the imagination.</p> <p>The only problem the article has is that it fails to distinguish between eustatic and relative sea level changes that would have both influenced the landscape of the Scilly Isles at the end of the end of the Late Devensian.</p> <p>Let me explain:</p> <p>Eustatic sea level change is sea level change that effects the entire world i.e. under stadial conditions more water is held in ice sheets, glaciers and permafrost so the sea level is low; and during interstadials less water is held in ice sheets, glaciers and permafrost so the sea level is higher, simple.</p> <p>Relative sea level change is caused by local forces and only affects a limited area. In the case of the Scilly Isles at the end of the last ice age the major influence on sea level in the area was the weight of the British Ice sheet on the earths crust. Ice sheets are heavy, and when this weight is loaded onto an area of crust it deforms it forming a depression under and close to the margins of the ice sheet. Around the margins of the depression the crust is displaced upwards, raising it above its previous level. This is the forebulge effect and it can extend several hundred miles from the depression (the extent is determined by how large the depression is i.e. the greater the depression the greater the displacement). When the ice sheet melts, the weight of the ice is removed from the crust and so the crust will slowly make its way back to the state of equilibrium that it was at before it was loaded with ice (generally speaking this state of equilibrium is never reached as usually another ice age will occur before it can do so). This process is known as glacio-isostacy.</p> <p>The Scilly Isles sit on the forbulge created by the Late Devnsion Ice sheet which is still in the process of correcting itself i.e. it is in effect sinking, causing a relative rise in sea level around the islands. It would have been this process combined with eustatic changes caused by the melting of the ice sheets, that would have been the cause of the inundation the lands inhabited by people during the Bronze Age. It is therefore inappropriate to consider sea level change around the Scilly Isles in the general terms used here as relative sea level change effects different parts of Britain in different ways, in some areas sea level is lowering (this is particularly obvious in Scotland), while in others it is rising (the south).</p> <p>This doesn’t help the Scilly Isles though, they are potentially extremely vulnerable.</p> An interesting piece, stories of lost cities and lands taken by the sea such as Lyonnesse, Cantref Gwaelod and Atlantis never fail to excite the imagination.

The only problem the article has is that it fails to distinguish between eustatic and relative sea level changes that would have both influenced the landscape of the Scilly Isles at the end of the end of the Late Devensian.

Let me explain:

Eustatic sea level change is sea level change that effects the entire world i.e. under stadial conditions more water is held in ice sheets, glaciers and permafrost so the sea level is low; and during interstadials less water is held in ice sheets, glaciers and permafrost so the sea level is higher, simple.

Relative sea level change is caused by local forces and only affects a limited area. In the case of the Scilly Isles at the end of the last ice age the major influence on sea level in the area was the weight of the British Ice sheet on the earths crust. Ice sheets are heavy, and when this weight is loaded onto an area of crust it deforms it forming a depression under and close to the margins of the ice sheet. Around the margins of the depression the crust is displaced upwards, raising it above its previous level. This is the forebulge effect and it can extend several hundred miles from the depression (the extent is determined by how large the depression is i.e. the greater the depression the greater the displacement). When the ice sheet melts, the weight of the ice is removed from the crust and so the crust will slowly make its way back to the state of equilibrium that it was at before it was loaded with ice (generally speaking this state of equilibrium is never reached as usually another ice age will occur before it can do so). This process is known as glacio-isostacy.

The Scilly Isles sit on the forbulge created by the Late Devnsion Ice sheet which is still in the process of correcting itself i.e. it is in effect sinking, causing a relative rise in sea level around the islands. It would have been this process combined with eustatic changes caused by the melting of the ice sheets, that would have been the cause of the inundation the lands inhabited by people during the Bronze Age. It is therefore inappropriate to consider sea level change around the Scilly Isles in the general terms used here as relative sea level change effects different parts of Britain in different ways, in some areas sea level is lowering (this is particularly obvious in Scotland), while in others it is rising (the south).

This doesn’t help the Scilly Isles though, they are potentially extremely vulnerable.

]]> By: auntiegrav http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52208 auntiegrav Fri, 31 Aug 2007 14:59:39 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52208 <p>The question I have is this: "What would the political and social environment be like if the sea was rising every year without knowing why or how?" We see that many ancient civilizations ended up living in hostile high altitude areas and we have wondered why they would do so, with perfectly good fertile land surrounding them below. Perhaps it was because they thought the sea was going to continue rising, and they wanted to get as far from it as they could.</p> The question I have is this: “What would the political and social environment be like if the sea was rising every year without knowing why or how?” We see that many ancient civilizations ended up living in hostile high altitude areas and we have wondered why they would do so, with perfectly good fertile land surrounding them below. Perhaps it was because they thought the sea was going to continue rising, and they wanted to get as far from it as they could.

]]> By: Jim http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52196 Jim Wed, 29 Aug 2007 20:51:58 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52196 <p>I stumbled on a book linked to this,</p> <p>My Dad is an amateur inter tidal archaeologist with a bit of a thing about sea levels.</p> <p>On his bookshelf was a book called "Floods, Famines and Emperors, El Nino and the fate of Civilisations" by Brian Fagan. I 'borrowed' it. I cannot fully comment on it as I haven't finished reading it yet.</p> <p>The general gist is a link between global weather patterns and the coming and going of civilisations and or historic events.</p> <p>So far not a bad read.</p> <p>If Robert needs a hand marking his blue line let me know, we have the technology</p> I stumbled on a book linked to this,

My Dad is an amateur inter tidal archaeologist with a bit of a thing about sea levels.

On his bookshelf was a book called “Floods, Famines and Emperors, El Nino and the fate of Civilisations” by Brian Fagan.
I ‘borrowed’ it.
I cannot fully comment on it as I haven’t finished reading it yet.

The general gist is a link between global weather patterns and the coming and going of civilisations and or historic events.

So far not a bad read.

If Robert needs a hand marking his blue line let me know, we have the technology

]]> By: Robert http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52194 Robert Wed, 29 Aug 2007 13:39:29 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52194 <p>Nice piece, Rob.</p> <p>Sudden sea level rise is one of my obsessions these days, too.</p> <p>I often see the increasingly unstable Greenland ice cap as a Damocles' sword - ready to deliver a sudden (in geological terms) - and from a Gaian viewpoint, not unwelcome - coup-de-grace to our civilization should we fail to make radical changes to halt climate change.</p> <p>I live at sea level (in a 3rd floor flat) and I have thought of painting a blue line on the housefront 7m above sea level to draw attention to the fact.</p> Nice piece, Rob.

Sudden sea level rise is one of my obsessions these days, too.

I often see the increasingly unstable Greenland ice cap as a Damocles’ sword – ready to deliver a sudden (in geological terms) – and from a Gaian viewpoint, not unwelcome – coup-de-grace to our civilization should we fail to make radical changes to halt climate change.

I live at sea level (in a 3rd floor flat) and I have thought of painting a blue line on the housefront 7m above sea level to draw attention to the fact.

]]> By: Mark http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/comment-page-1/#comment-52193 Mark Wed, 29 Aug 2007 10:07:01 +0000 http://transitionculture.org/2007/08/29/the-rise-and-fall-of-sea-levels-and-civilisations/#comment-52193 <p>I also watched that show on India, really interesting. I was wondering if the fall of the Sumerian Empire and their potential migration fallout may also have had an influence on the subsequent collapse of the Indus Valley Civilization and their migration. The two events appears to be in a similar 300 odd year period. There was also a fascinating show on finding a lost city of Egypt a while back. They found it by looking at where the delta rivers were located in the past and summised that that particular Egyptian dynasty collapsed because they invested so much into trying to preserve their capital city against the shifting river. This obviously points to the need to view climate and ecology as the fundamental dictators on civilization and that adaptation through a balance of decentralised power and freemdom for self-organisation are key. Now there is talk of building another Thames barrier and i wonder if these lessons will ever be learnt when each generation fights to maintain view of a static world.</p> I also watched that show on India, really interesting. I was wondering if the fall of the Sumerian Empire and their potential migration fallout may also have had an influence on the subsequent collapse of the Indus Valley Civilization and their migration. The two events appears to be in a similar 300 odd year period. There was also a fascinating show on finding a lost city of Egypt a while back. They found it by looking at where the delta rivers were located in the past and summised that that particular Egyptian dynasty collapsed because they invested so much into trying to preserve their capital city against the shifting river. This obviously points to the need to view climate and ecology as the fundamental dictators on civilization and that adaptation through a balance of decentralised power and freemdom for self-organisation are key. Now there is talk of building another Thames barrier and i wonder if these lessons will ever be learnt when each generation fights to maintain view of a static world.

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