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Earth Science

Huge Canyon Discovered Under Greenland Ice 137

Posted by timothy
from the earth-the-present-frontier dept.
cold fjord writes with this news, straight from the BBC: "One of the biggest canyons in the world has been found beneath the ice sheet that smothers most of Greenland. The canyon — which is 800km long and up to 800m deep — was carved out by a great river more than four million years ago ... It was discovered by accident as scientists researching climate change mapped Greenland's bedrock by radar. The British Antarctic Survey said it was remarkable to find so huge a geographical feature previously unseen. The hidden valley is longer than the Grand Canyon in Arizona. ... The ice sheet, up to 3km (2 miles) thick, is now so heavy that it makes the island sag in the middle (central Greenland was previously about 500m above sea level, now it is 200m below sea level)."
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Huge Canyon Discovered Under Greenland Ice

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  • So just wondering... (Score:5, Interesting)

    by Daetrin (576516) on Thursday August 29, 2013 @04:59PM (#44710539)
    In theory, if all the ice on Greenland melted, how long would it take Greenland to spring back up again? I'm presuming it wouldn't be instantaneous or even noticeable to a human on Greenland at the time (well, aside from the earthquakes that would almost certainly accompany such an event,) but are we talking years, decades, centuries, or longer?
    • by necro81 (917438) on Thursday August 29, 2013 @05:17PM (#44710753) Journal
      Centuries to millennia. Geologists are able to measure the ongoing rebound [wikipedia.org] of North America from the retreat of the glaciers from the last ice age.
    • by Anonymous Coward on Thursday August 29, 2013 @05:21PM (#44710817)

      Millennia. The post-glacial rebound [wikipedia.org] is still happening in North America from the last ice age [wikipedia.org], and that was 10,000 years ago. The New Madrid Seismic Zone [wikipedia.org] is still active today, and experts agree that it has the potential to produce another very powerful earthquake.

      • by RockDoctor (15477)
        [Wearing my hard hat that says "Geologist" on the front.]

        I've not seen substantive evidence that the New Madrid earthquakes were related to post-glacial rebound stresses. What is the source of the stresses in that part of central North America, I certainly don't know, and I've never seen any convincing arguments from someone who claims that they do know (but ... it's not my continent, so I may have missed something in the couple of years since I last looked).

        OTOH, the 1927 IIRC "Grand Banks" earthquake [E

    • Re: (Score:2, Interesting)

      by Anonymous Coward

      Some places in Sweden are raising with 9mm/year so it could probably be noticed by humans over a lifetime.

      • Noticeable is an understatement

        That's 35 inches in 100 years.

        I hope it's even!

        • by jopsen (885607)

          Noticeable is an understatement

          That's 35 inches in 100 years.

          I hope it's even!

          Or 9mm per year, 9cm per 10 years, 0.90m per 100 years, to be exact...

          • I doubt the 9mm is exact, so your precision is ... not.

          • Re: (Score:3, Informative)

            by PurpleAlien (797797)
            High Coast (Sweden) and Kvarken Archipelago (Finland)

            "The geomorphology of the region is largely shaped by the combined processes of glaciation, glacial retreat and the emergence of new land from the sea which continues today at a rate of 0.9 m per century."

            Source: http://whc.unesco.org/en/list/898 [unesco.org]
            • Re: (Score:2, Interesting)

              by Anonymous Coward

              in finland Limingan lahti is famous place it has even "bird sighting places" and along the way to bird-tower theres signs where sealevel used to be... its quite remarkable how much land has risen from sea :D

      • by mevets (322601)

        9mm/yr after how many years?
        The shape of the curve is probably more interesting; as the awkwardly phrased wikipedia page attests:
        ----
        Studies have shown that the uplift has taken place in two distinct stages. The initial uplift following deglaciation was almost immediate due to the elastic response of the crust as the ice load was removed. After this elastic phase, uplift proceeded by slow viscous flow so the rate of uplift decreased exponentially after that.
        -----
        I think it would be quite observable.

        • by RockDoctor (15477)
          There are several exposed fault scarps in northern Sweden and Norway on otherwise polished flat (by the glaciers) landscapes which indicate that some of the isostatic rebound has taken place (almost) instantaneously.

          From http://www.sgu.se/dokument/service_sgu_publ/C836.pdf [www.sgu.se] comes this caption:

          fig. 18. The Parvie fault at Lake Kamasjaure, some 70 km north of Kiruna. The c. 8 m high fault scarp forms steeply overhanging cliffs indicating reverse fault movement. See helicopter for scale.

          The whole publication

    • by Anonymous Coward

      Michigan and Upper New York are still rebounding from the last ice age.
      It will take a while. Today, typical uplift rates are of the order of 1 cm/year or less.
      http://en.wikipedia.org/wiki/Post-glacial_rebound

    • by icebike (68054) on Thursday August 29, 2013 @05:30PM (#44710927)

      In theory, if all the ice on Greenland melted, how long would it take Greenland to spring back up again? I'm presuming it wouldn't be instantaneous or even noticeable to a human on Greenland at the time (well, aside from the earthquakes that would almost certainly accompany such an event,) but are we talking years, decades, centuries, or longer?

      It would be noticeable by humans over their life span.

      You see this (in smaller scale) in places in Alaska where receding ice caps and the glaciers that flow from them slowly recede up the valleys and vegetation changes appear in the wake.

      You also see the river flowing from the glaciers cutting deeper channels to the ocean. The glaciers flowed directly to the ocean earlier, now the glacier's nose is several miles upstream. The river channels "grow" high banks as you travel away from the glacier toward the ocean. This is a sign of uplifting land, (there are no longer and deposited soils being laid down in the area, yet the river banks grow steeper, and the river surface is within a few feet of mean high tide over the years.

      Its not much, but you can see it over a period of 30 or 40 years if you are observant. Surveyors can measure it these days (even without GPS), relative to mean high-tide in those places where survey markers were installed decades ago.

      • I was hoping there would be a decent answer to this question. I was curious about the answer and this explains it best to me.

      • Re: (Score:2, Interesting)

        by ianare (1132971)

        You are describing glacial retreat caused by global warming, which is not the same thing. As temperatures rise, the ice melts and retreats higher in elevation where it is colder. Also as a result of the warming effect, plants are able to take up residence in land formerly occupied by the ice sheet. In areas with permafrost, some of it will melt, leading to sinking and fractures in infrastructure. Climate change can happen very quickly, as we are seeing.

        An example of glacial rebound would be a fishing villag

        • by icebike (68054)

          But it is the same thing, as any geologist will tell you. Its just on a smaller scale.

          A bazillion tons of ice is lifted from the land, and the land rebound upward. Entire icefields that feed the glaciers also reduce their mass.
          And it is clearly visible in a life time, not merely by observing land features previously hidden by the glacier, but also, as I mentioned, the
          increased height of the stream banks and surrounding land.

          Remember, there are no alluvial deposits taking place.
          The stream WAS and STILL IS

    • dunno, but there is a seesaw effect still in play in Western Europe; the most dramatic effect is seen along the length of mainland Britain. While Scotland is still rising after spending a while under a couple miles of ice, the South of England is sinking as it was largely ice-free during the last big freeze. The phenomenon is slow, it's taking a few thousand years for a complete oscillation, but geological evidence suggests that prior to the last ice age, the North Sea was bone dry (being several hundred me

      • by mrbester (200927)

        The south of England, particularly the Weald and south coast from Dover to Selsey, was under the sea until the Cenozoic era, hence the chalk downs and cliffs made of crushed fossilised prehistoric sea shells. To say there must have been a few of them is an understatement; Beachy Head is 513ft high. And that's after tens of millions of years of erosion.

      • by RockDoctor (15477)
        Sorry, but you're wrong on a number of counts.

        I'm a geologist who has spent most of the last 30 years working in the North Sea, and living and walking in Scotland.

        but geological evidence suggests that prior to the last ice age, the North Sea was bone dry (being several hundred metres above sea level!).

        Most of the North Sea has been a basin of marine deposition for the last 100-odd million years. The last time that the Northern North Sea was emergent was in the late Jurassic with the deposition of the Ness

    • by hydrofix (1253498)
      During the last ice age up to only 15,000 years ago, the whole of Scandinavia was covered under a very heavy glacial mass, causing the earth's crust to deform. In these areas, the earth is currently raising or rebounding [wikipedia.org] at a rate of about 3-5 millimeters per year, or up to 10 inch (25 cm) in half a century (50 years). Such changes are indeed quite visible during a human life. An elderly person might recognize that a shore where he or she used to spend time as a child has visibly changed as if by a permanen
    • by riverat1 (1048260)

      The Canadian Shield is still rising from the end of the last glaciation around 12,000 years ago. Lake Champlain used to be part of the Champlain Sea [wikipedia.org] until isostatic rebound caused it to rise above sea level around 10,000 years ago.

    • by DrXym (126579)
      Earthquakes are still occur in Ireland, the UK and Scandinavia from glacial rebound. They are very minor quakes in modern times but they're still frequent events. I assume that Greenland would experience quakes and possibly quite violent ones to begin with.
    • by Pav (4298)
      Dr Iain Stewart has done some fantastic BBC documentaries on geology, and I believe he has answered exactly this question. The movement takes millenia, but sometimes there are huge earthquakes in the middle of nowhere far from plate boundaries. This [youtube.com] may be the relevant documentary.
    • by T.E.D. (34228)

      The Northern parts of North America and Europe are still springing back up [wikipedia.org] from the last Ice Age, 20,000 - 8,000 years or so ago.

      So it may take a little while.

    • by RockDoctor (15477)

      In theory, if all the ice on Greenland melted, how long would it take Greenland to spring back up again?

      [...]are we talking years, decades, centuries, or longer?

      The Laurentide ice sheet (over NE Canada) melted fairly rapidly (a couple of centuries) around 9000 years ago, as indicated by deposits of ice-rafted debris in the middle of the North Atlantic (without iceberg transport, how are you going to transport mm-size sand grains to the middle of an ocean? Let alone fist-sized "drop stones".). There's also a

  • by 50000BTU_barbecue (588132) on Thursday August 29, 2013 @05:00PM (#44710551) Homepage Journal
    Is it where the Wunderland Treatymaker was test fired?
  • by themushroom (197365) on Thursday August 29, 2013 @05:00PM (#44710555) Homepage

    Now's the time when climate change could do some good... RAISE GREENLAND! Make it green land!

    • by Kjella (173770)

      And only 1031 years after it was named so in order to trick people into immigrating there, better late than never I guess.

  • by pollarda (632730) on Thursday August 29, 2013 @05:04PM (#44710603)
    With a little global warming one of the world's greatest landmarks could be recovered, the sag in central Greenland would be fixed and a new source of income for Greenland could be tapped as tourists flock to this new "Grand Canyon" to go hiking, fishing, and camping.
    • Re: (Score:3, Funny)

      by Anonymous Coward

      Based on my own experience, once there's sagging in the middle it never goes away no much how hard you try to burn off the weight.

    • And the rest of Canada, Alaska, and Siberia. By that time we will have robots serving us sp it's all irrelevant. Bring on the robots as fast as possible.

    • Wouldn't that be the Green Canyon?

  • More info (Score:3, Informative)

    by cold fjord (826450) on Thursday August 29, 2013 @05:05PM (#44710611)

    Giant Canyon Discovered Under Greenland Ice Sheet [nationalgeographic.com]

    While flying over the ice sheet, scientists over the past three decades have measured the depths of the canyon using a radar system that operates at frequencies transparent to radio waves—from around 50 megahertz to 500 megahertz. A pulse of energy is sent down to penetrate through the ice, bounce off the bedrock, and travel back to the radar system. (Also read: "'Shocking' Greenland Ice Melt: Global Warming or Just Heat Wave?")

    'Grand Canyon' of Greenland Discovered Under Ice Sheet [livescience.com]

  • that Greenland is called Green again?
    • Re:Why is it (Score:5, Informative)

      by Ioldanach (88584) on Thursday August 29, 2013 @05:18PM (#44710765)

      that Greenland is called Green again?

      Propaganda. Erik the Red named it that in 985 AD to get people to colonize it with him.

      • Re: (Score:1, Interesting)

        by Anonymous Coward

        And despite what you've been taught, it was a successful farming colony until the climate cooled and the route north of Great Britain became too hazardous.

        • by riverat1 (1048260)

          I think you'd have to say it was a marginal farming colony. I've never heard any indication they had enough surplus to export.

          • by dwye (1127395)

            No, but they were successful enough to attempt settling Vinland, and to send roughly-yearly lumbering expeditions for a century after the Skralings chased them out. Their surpluses probably went into internal growth until the climate change suddenly made life untenable, there. If they had learned more from the eskimos they might have been able to keep going.

            • No, but they were successful enough to attempt settling Vinland, and to send roughly-yearly lumbering expeditions for a century after the Skralings chased them out. Their surpluses probably went into internal growth until the climate change suddenly made life untenable, there. If they had learned more from the eskimos they might have been able to keep going.

              Surplus? They never made enough off of farming, and had to supplement with hunted animals, mostly seals, even when they arrived.

              http://news.ku.dk/all_news/2012/2012.11/greenland_norse_gorged_on_seals/ [news.ku.dk]

      • I had always heard that the residents of Iceland named it, in order to trick Viking raiding parties.

        No citation, pure heresay.

  • Well, I'm sure the hardcore LARPers are packing their bags already because that sounds so RPG/D&D cliche to me. Get your authentic adventuring rowboat and let's go!
  • by Alsee (515537) on Thursday August 29, 2013 @05:14PM (#44710713) Homepage

    was carved out by a great river more than four million years ago

    More lies straight from the pits of hell.
    Obviously this super-canyon was carved during Noah's flood.
    Another Win for Flood geology!

    -

  • I've read and heard that the salinity of the ocean drives a large part of the currents. The entire premiss of the over-the-top disater film "Day after Tomorrow" was that warming would dump fresh water into the N. Atlantic shutting down the salinity driven currents (that draw the warm Gulf steam northward and thereby warm the N hemisphere) leading to a deep freeze in the N Hemisphere. Granted that was a bit of far fetched fiction. But does knowing that ice-melt will follow the canyon and dump into the relati
    • by RockDoctor (15477)

      But does knowing that ice-melt will follow the canyon and dump into the relatively self-contained arctic instead of the N. Atlantic change real-word global-warming models?

      Not hugely, since the north-flowing glacier (and probably sub-glacial drainage in this region too) empties into the Arctic Ocean, as you say, but the main area for the formation of "North Atlantic Deep Water" is the area between Greenland, Iceland, Northern Norway, and Svalbard.

      There is noticeable (and fairly worrying) instability in the

  • Accident? (Score:4, Insightful)

    by TechyImmigrant (175943) on Thursday August 29, 2013 @05:18PM (#44710769) Journal

    > It was discovered by accident as scientists researching climate change mapped Greenland's bedrock by radar.

    If you discover a canyon while scanning the bedrock with radar, that isn't an 'accidental' discovery. An accidental discovery is when you're looking for a dropped contact lens and come across a canyon instead.

  • by Ioldanach (88584) on Thursday August 29, 2013 @05:24PM (#44710847)
    "If the Greenland ice sheet melts completely it will raise global sea level by 7 metres and swamp many major cities" (article)

    Does this account for what would happen when Greenland floats back up?

    • You're joking? Or assuming that the compression of Greenland is mainly water being squeezed out and not rock being compressed?

      • by Ioldanach (88584)
        If an area the size of Greenland is depressed 300 meters, I'd wonder if it is deformation of the Earth's crust and the whole thing could be pushed back up by internal pressures when the weight is gone. Not assuming anything, just wondering if that could happen and what the impact on sea levels would be if it did.
        • The rock and magma displaced when Greenland sank might (more or less) return from wherever it went. If that area were below the seabed immediately surrounding Greenland, the ocean in that area would get slightly deeper, partially counteracting the increased ocean level (probably about 1/3 in the long term.) However, islands near Greenland might sink along with the ocean floor.

          On the other hand, if the ocean floor near Greenland is relatively still, the closest islands might rise along with Greenland.

          I can i

      • by RockDoctor (15477)
        As ChrisMaple points out below, there is very little compression of the rock itself. What is happening is that the relatively weak rock around 100-300km below the surface (the asthenosphere, from Greek "a-" (negator), "sthenos-" (strength) and "sphere" (sphere)) is displaced laterally, causing lifting of the seabed around the depressed continent. It flows back on a time scale of millennia because it has stiffness that would make toffee or asphalt look like water.
        • Thanks that's interesting.

          Though however large the effect is, I think it has to reduce the sea level by significantly less than the amount that's it raised by the added water.

    • by mrvan (973822) on Thursday August 29, 2013 @06:01PM (#44711275)

      The sea level rises because the stuff covering Greenland is ice. When it melts it flows into the ocean, raising sea levels. Greenland is around 2M km2, and the ice sheet is around 2km thick, so we're talking about 4 million cubic kilometers of water. Earth has around 361 sq kilometers of water, so spreading the water around the earth gives around 10 meters of ice on each meter of water, or around 9 meters of water. In other words, (1) greenland is huge, and (2) the sea level rise is purely ice flowing into sea and has nothing to do with geological changes.

      Greenland rebounding does absolutely nothing because the "extra" volume is not taken out of the ocean. The water doesn't suddenly jump back up on the land.

      (arctic ice melting does not affect sea levels because the weight of the ice is already displacing water. Antarctic ice and glaciers on land are in the same situation as greenland ice)

      • by dkf (304284)

        Greenland rebounding does absolutely nothing because the "extra" volume is not taken out of the ocean. The water doesn't suddenly jump back up on the land.

        Not true. You can get shifting in the surrounding rock as things move around, though the effects are complex. There's also the differences due to the change of the local gravity field; all that ice has a lot of mass and does currently attract plenty of seawater to it.

        I have no idea what the relative sizes of these effects are likely to be.

        • by Kjella (173770)

          Not true. You can get shifting in the surrounding rock as things move around, though the effects are complex.

          It's earth's crust rising out of the mantle, if anything the surrounding seabed will rise slightly with it, certainly not the other way around.

          There's also the differences due to the change of the local gravity field; all that ice has a lot of mass and does currently attract plenty of seawater to it.

          Extremely minimal, even if you have 2km sideways pull from the ice there's 6400km of downwards pull towards the center of the earth so water doesn't gather much Heavy mineral deposits or a thick crust directly under the water is different, that adds more compression without trying to counteract the sideways forces.

          • by dkf (304284)

            There's also the differences due to the change of the local gravity field; all that ice has a lot of mass and does currently attract plenty of seawater to it.

            Extremely minimal, even if you have 2km sideways pull from the ice there's 6400km of downwards pull towards the center of the earth so water doesn't gather much Heavy mineral deposits or a thick crust directly under the water is different, that adds more compression without trying to counteract the sideways forces.

            I can't find the article I was thinking of right now, but this one [piecubed.co.uk] is not too far off.

      • by Nidi62 (1525137)
        Don't forget to take this canyon into account. When all the ice melts, the water will just fill up the canyon instead of all of it going into the ocean. Maybe I should set up a bottling plant there. A bunch of people will pay good money to drink "pure glacier water". I'll be rich :)
      • by Thomasje (709120)

        Greenland rebounding does absolutely nothing because the "extra" volume is not taken out of the ocean. The water doesn't suddenly jump back up on the land.

        It is true that Greenland rebounding won't affect sea level, but not for the reason parent seems to imply. The real reason is that when a land mass is pressed downwards by an ice sheet, it sinks because it displaces material in the mantle. That mantle material is squeezed out sideways, and ends up raising adjacent land masses or ocean floor.

        When the ice sheet melts, the displaced mantle flows back, the depressed land rebounds, and the raised adjacent land or ocean floor sinks back.

        This effect is current

        • by riverat1 (1048260)

          Mod parent up. I was going to post the same thing. You can see the effect in North America because land north of New Jersey on the East Coast is still rising from the end of the last glaciation while south of NJ land is sinking in a seesaw effect.

    • by cusco (717999)
      No, nor for when Antarctica rebounds. It's such a slow process that i don't think it will make much difference unless you're looking at it on a time scale of centuries.
    • by RockDoctor (15477)

      Does this account for what would happen when Greenland floats back up?

      The major cities of Greenland (pop. 56000) will rise back above sea level.

  • Who cares? Someone will just come along and fuck it up.
  • by agm (467017)

    I find the idea of ice 3km thick to be mind boggling!

  • by Type44Q (1233630)

    Huge Canyon Discovered Under Greenland Ice

    And to think: they didn't even need to roll it in flour.

    cha-ching...

  • I hope to Cthulhu this means we'll discover shoggoths next.

    • Maybe HPL should have started his stories out with a variation of the standard crime re-enactment disclaimer: "Some names and places have been changed to protect the sane."

  • by steelfood (895457) on Thursday August 29, 2013 @06:38PM (#44711629)

    First time I saw the title, I read it as "Huge Crayon Discovered Under Greenland Ice"

  • by Anonymous Coward

    If there is a giant, ancient river bed across Greenland, that means it has a delta where it dumped into the ocean at its discharge end a long time ago. Find that ancient delta and drill for oil "downstream" of it. Petroleum, is primarily formed from zooplankton and algae getting buried under sedimentary rock for ages, and this process happened greatest where ancient river deltas (and even present deltas) are found.

  • Our friends at Goddard's Scientific Visualization Studio produced a short animation [nasa.gov].
  • So that's where sublime creamy sauce I coat my hot wings comes from! The Hidden Valley Ranch production site has been found!

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