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Thread: Earthquakes

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    Default Earthquakes

    I think San Francisco is about due for another "big one".
    The new bridge is up so now all we need is a good size event to test it out.

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    Yes I am an agent of Satan, but my duties are largely ceremonial.

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    By 'Everything' I have read on the San Andreas fault, it along with the fault under Yosemite National Park is WAYYYYYY over due for a 'BIG BLOW'.
    I never linked Mt St Helens, Yosemite and the San Andreas fault as all being connected and of course they are the eastern side of the 'Pacific Ring of Fire.
    I am sorry to have to admit it was one of those God Awful cataclysmic movies where the hero/heroine saves the world with a bucket of sand and 2 candles which piqued my interest to actually LOOK and see and read the subterranean history of that part of the "Ring of Fire".
    If the geologists are correct, the last eruption at Yosemite was incredibly huge, blowing out a vast area and they claim such eruptions had occurred at fairly regular intervals in the past but for some reason, it is 'overdue'.
    The old joke is that when St Andreas does finally happen, Arizona will be the new west coast of America.
    If we just have a massive earthquake and the fault does open and swallow California, it would cause an unimaginable monstrous Tidal wave who knows how many times bigger than either the Indonesian or Japanese ones were but its survivable, BUT if we had a massive eruption in Yosemite, just what effect would that have on the Earth as a whole when we see how far the 'Dust Clouds' of recent small volcano's have covered.
    If either happens, I dont think our worries about either Ford or Holden closing down would last more than a few seconds, do you?
    ***************
    Saw those Doco's on building Bridges and buildings with counterweights, flexible joints and rollers, now to see just what holds up when the 'Big One' finally happens.
    Last edited by gordon_s1942; 10-03-14 at 12:16 AM.
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    That page was fun, i couldn't find anything to last a 9.0 on the San Andreas fault, that magnitude pretty much destroys any standing structure....

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    Mine fell down too.
    I felt like I was playing the kids game where at the end they say, 'All Fall Down'.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    After a few goes of trial and error, I could most of my bridge to hold together at 8.5
    I lost a few pedestrians in the bay but I'm sure they can swim to shore.

    As much as some of us would love to see California be swallowed up by the Pacific ocean, it just ain't going to happen in one giant event

    Closer to home, we still have 'dormant' volcanoes in Australia. The Pacific plate pushes under the Australasian plate along the eastern side.
    This of course is what helped form New Zealand and the Great Dividing range.

    Atherton Volcanoes, The Western Victorian and South Australian volcanoes are all geologically recent (<10,000 years).
    I took a quick sneak peak at the Victorian volcano discovery centre in .... where the hell was that ? ummm... Penshurst Vic. Yeah, it's a small town !


    On one of their brochures they have an (edited) picture of a volcano erupting in Lake Purrumbete with Colac in the background.
    It makes a pretty good point not to neglect dormant volcanoes.
    Even so there appears to be no sign of magma movement under the Australian mainland for the time being.

    Damn !
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    Now it's Trash the
    In hindsight I should have posted my Facebook status as: "I've blown the head gasket on my 1997 XR3i" rather than "I've just buggered a 14 year old escort".
    The police still haven't seen the funny side, my lap top's been confiscated and the wife has gone off to her mum's.

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    Mt Canobolas at Orange is whats left of an ancient 'extinct' volcano on which I think is the western end of a volcanic area that starts about 10kms to the East.
    As you drive along the Mitchell Highway just east of Lucknow, the soil changes colour and the geology begins to show lava flows and foldings along with signs the rocks have been superheated because of their colouring and riddled with holes I think is caused when internal gas' escape.
    I did read a claim that said this line that runs from North Queensland where those Lava tunnels are, through here and into Victoria and when 'Gwandonaland' after leaving Africa and 'drifted' across what is now the Indian Ocean, it passed over a 'fault line' that caused these volcanic remnants we see today, but I find that a bit odd as why didnt other areas between here and Perth get punctures too as the plate only seems to move 30mm (1 inch) a century at full speed.
    I have to say I was very surprised to see just peppered Victoria is with fault lines and signs of ancient volcanic activity.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    Mt Canobolas is just one of many volcanoes in NSW Gordon. It's not specific to any particular volcanic area and the formations that make up the soil around the Eastern side is a mixture of more ancient under sea formations (quartz where the gold and copper loads are found) Limestone from later coral reefs and shallow under sea formations and the top soil which is more red/brown in appearance which is sedimentary and alluvial soil deposited from old man Canobolas.

    There are the major volcanoes down the great dividing range which are obvious that they were once volcanoes. Mt Warning, Mt Lindesay, Mt Kaputar and the Warrumbungles.
    Big volcanoes with obvious cone or dome structures.
    Volcanoes like Canobolas, Dubbo and Byrock are a little less obvious. There are hundreds of these smaller volcanoes all around NSW. Not far from where I live I can think of at least 30.
    And then there are the truly massive volcanoes along the range which you don't notice because they were so big and now eroded down to large domes.
    Ebor, Walcha, Barrington, Mittagong, Snow Mountains are just some of the big ones that are hard to pick.
    At the other end of the scale are tiny little ones like Machines Crater near Glenbrook. Hard to believe that this small depression in a sandstone base was ever a volcano.

    The continent can't pass over a "fault line". Faults are basically cracks in the crust, the crust doesn't move over them. You may be thinking of a hot spot or a mantle plume which powers
    volcanoes like the Hawaiian volcano chain. In the case of the Australian east coast volcanoes it might appear that they are fed by one hotspot as the Australian continental plate moves north
    forming volcanoes but it isn't the case of one hot spot. With the pacific plate pushing westwards underneath the Australia plate it forms multiple hot spots and the continent moves north over those.
    This is why the volcanoes down the range are not linear in age with the Queensland volcanoes being older than Tasmanian volcanoes.
    The Atherton and South Australian volcanoes are recent and Cradle Mountain and Canobolas etc are much older.

    Ancient isn't the description I use for Victorian volcanoes. "Recent" is the word I generally use.
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    Trash, the article I read made the claim that the plate Australia sits on 'passed over' this fault line and that caused the line of volcanic disturbances but as I said it seemed a bit far fetched to me.
    When I use the term 'Ancient', I mean older than me or (in this case pre human habitation of Australia.) VERY major mistake there after reading that Wikipedia site !!!
    One thing for sure is you cant have volcanic activity and Coal seams and I sit just a few kilometres south of the Western Coal fields so now ( I am going to have to read up on what came first geologically.)
    Again it would appear if I read those dates correctly, the Coal would have been laid down after the volcanoes ceased to erupt.

    Unfortunately the coal fields seem to have attracted the Coal Seam Gas companies as they are applying for 'exploratory drilling permits'.
    Last edited by gordon_s1942; 13-03-14 at 12:09 AM.
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    Actually, the Coal and Volcanoes are not mutually exclusive. In geological terms, the two can even form at the same time.
    The scenario would be to have a swampy forest. Lets call it "The Dagobah forest"
    Then just up the road we have a plume rise in the mantle and burst through the crust.
    The ash and lava flow build the volcano and bury the surrounding forest. The layers above continue to grow from either volcanic or alluvial deposits.
    The volcanic deposits can be put down before or after the coal forms. An example I can think of off the top of my head is the Hunter Valley coal seams.
    There are two main coal seams from memory. The upper seam is about 250 million years old and the lower layer about 400 million years.
    In between these layers are of course sand stone and volcanic tuft (ash). A lot can happen in 200 million years

    And there's nothing stopping the coal from existing after a volcano intrudes through the layer. In the immediate vicinity we might think of the coal seam catching fire and burning out the entire seam.
    But this doesn't happen. The seam can catch fire but remember that the fire needs oxygen or another oxidiser to continue burning. The volcano itself will plug the seam cutting off any supply of air.
    And even if the coal seam burns for 10,000 years this is still a drop in the bucket compared to the lifespan of some of these volcanoes.

    Mt Kaputar (Nandewar Volcano) is a good example. This volcano pushed up from the western plains about 22 million years ago.
    The coal seam surrounding it is the same seam of the Bowen basin that pretty much runs all the way to Wollongong.
    Underneath the volcano I would expect to find a transition in the coal seam to some kind of metamorphic rock which then transitions to a basaltic intrusion or dyke.
    The coal layer may also be thrust up, but I can't think of anywhere around Mt Kaputar where the coal comes to the surface like it does in the hunter valley.
    But outside of that immediate area the coal is pretty much un-effected.

    The black areas are 'recent' volcanic areas. Recent being <~100 million years.
    Yes I am an agent of Satan, but my duties are largely ceremonial.

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