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Thread: If ice ages are cyclic...

  1. #1 If ice ages are cyclic... 
    Forum Ph.D. Raziell's Avatar
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    ...wont the area around equator be the only livable area when the next one comes?


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    And when will the next Ice Age occur? And what's your evidence for that?


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  4. #3  
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    I thought they were cyclic after seeing a show about it on discovery channel. But this isnt even proven?
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    Time Lord Paleoichneum's Avatar
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    it would depend on if we are currently at the end of this glacial cycle , or are only in one of a number of interglacial periods in the cycle. If it is the end, thene there is not telling how many million years may pass before another glacial period happens. If we are in an interglacial, then the equitorial regions and the southern hemisphere are the most equitable places for life, while the habitability of North America and Eurasia will depend on the extent of glaciation.
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    Forum Radioactive Isotope skeptic's Avatar
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    The last million or so years has been one Ice Age. Within that million years were about 10 cold glacial periods with warm interglacial periods between. We are currently in an interglacial period, which is about 12,000 years old. Glacial periods seem to last about 100,000 years. The last interglacial was 120,000 years ago.

    Before a million years back, outside the Ice Age, temperatures were warm and equable. There have been other Ice Ages, but they are separated by periods of tens or hundreds of millions of years. There has even been a period called Snowball Earth, where the conditions were so cold that some people believe the equator was covered with snow and ice. As far as I know, it is glacial/interglacial periods within one IceAge that are cyclic. Ice Ages themselves do not seem to follow a regular pattern.

    There is a school of thought that says our current interglacial period will, in fact, mark the end of this Ice Age, due to global warming and human influence. I guess only time will tell.
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  7. #6  
    Forum Ph.D. Raziell's Avatar
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    Quote Originally Posted by skeptic View Post
    The last million or so years has been one Ice Age. Within that million years were about 10 cold glacial periods with warm interglacial periods between. We are currently in an interglacial period, which is about 12,000 years old. Glacial periods seem to last about 100,000 years. The last interglacial was 120,000 years ago.

    Before a million years back, outside the Ice Age, temperatures were warm and equable. There have been other Ice Ages, but they are separated by periods of tens or hundreds of millions of years. There has even been a period called Snowball Earth, where the conditions were so cold that some people believe the equator was covered with snow and ice. As far as I know, it is glacial/interglacial periods within one IceAge that are cyclic. Ice Ages themselves do not seem to follow a regular pattern.

    There is a school of thought that says our current interglacial period will, in fact, mark the end of this Ice Age, due to global warming and human influence. I guess only time will tell.
    Very informative, thanks!
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    It is my understanding that the current ice age began 2.8 million years ago. While we are in an interglacial period, the ice age itself has not gone away. How do we know that? By definition, continental ice sheets and polar caps mean the earth is in an ice age. We have both, plus a lot of sea ice. The normal condition of the earth is ice free with a temperature differential from equator to poles about half what it is today. In other words, forests at both poles would indicate we are not in an ice age. We are far from that. We need an increase of a good six degrees to break out of the cycle and put an end to the ice age. I have uploaded a lot of info about this: http://www.buildart.com/ice_free_earth_now.htm
    Last edited by rbissett; October 21st, 2011 at 01:50 PM.
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    It might be more acurate to say ice ages are recurrent rather than cyclical. The time between ice ages is not known to be uniform so the occurance of the ice age is not cyclical but recurrent.
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    Quote Originally Posted by Sealeaf View Post
    It might be more acurate to say ice ages are recurrent rather than cyclical. The time between ice ages is not known to be uniform so the occurance of the ice age is not cyclical but recurrent.
    ...and it's glacial periods occurring with in the ongoing ice age, rather than recurring ice ages.
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    Quote Originally Posted by rbissett View Post
    Quote Originally Posted by Sealeaf View Post
    It might be more acurate to say ice ages are recurrent rather than cyclical. The time between ice ages is not known to be uniform so the occurance of the ice age is not cyclical but recurrent.
    ...and it's glacial periods occurring with in the ongoing ice age, rather than recurring ice ages.
    Three Wiki links:

    Timeline of glaciation - Wikipedia, the free encyclopedia

    Sangamonian (stage) - Wikipedia, the free encyclopedia

    Wisconsinan glaciation - Wikipedia, the free encyclopedia

    We know the most about the most recent episodes. The older ones evidence being partially destroyed, mostly by the Illinoian glaciation which extended farther south in North America, in most cases, than the Wisconsinan. The Sangamonian interglacial lasted long enough that its' strata generally shows pronounced soil development (an A soil).
    I'm sorry, my responses are limited. You must ask the right question.

    "The track of a glacier is as unmistakable as that of a man or a bear, and is as significant and trustworthy as any other legible inscription"
    John Strong Newberry; 1873

    "From observations upon living glaciers, and from the known nature of ice, we may learn to recognize the track of a glacier as readily and unmistakably as we would the familiar foot-prints of an animal." G. F. Wright 1891 (108-109)

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  12. #11  
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    the world as a whole has been getting cooler since the end of teh Jurassic.

    Deep ocean water - Wikipedia, the free encyclopedia

    http://www.cgd.ucar.edu/ccr/brady/deepwater.pdf
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    Granpa, I think that should be 'was getting cooler'. The anthropocene, with the overlaying of human influence over natural processes has already irrevocably changed the both the timetable as well as direction of climate change.
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    Quote Originally Posted by Ken Fabos View Post
    The anthropocene, with the overlaying of human influence over natural processes has already irrevocably changed the both the timetable as well as direction of climate change.
    irrevocably ? maybe on a human time scale - on a geological time scale your so-called anthropocene is a mere thin extinction marker bed, a blip in the geological column
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  15. #14  
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    Quote Originally Posted by marnixR View Post
    Quote Originally Posted by Ken Fabos View Post
    The anthropocene, with the overlaying of human influence over natural processes has already irrevocably changed the both the timetable as well as direction of climate change.
    irrevocably ? maybe on a human time scale - on a geological time scale your so-called anthropocene is a mere thin extinction marker bed, a blip in the geological column
    I agree and would remind all that besides us, the Earth's obliquity is also declining, currently, both affecting climate.
    I'm sorry, my responses are limited. You must ask the right question.

    "The track of a glacier is as unmistakable as that of a man or a bear, and is as significant and trustworthy as any other legible inscription"
    John Strong Newberry; 1873

    "From observations upon living glaciers, and from the known nature of ice, we may learn to recognize the track of a glacier as readily and unmistakably as we would the familiar foot-prints of an animal." G. F. Wright 1891 (108-109)

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    Eccentricity or our orbit is also declining. Astronomical forced changes are pretty mild over the next 40,000 years.
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  17. #16  
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    The much diminished biodiversity is but one of our legacies and by that alone the future of our world is indeed irrevocably changed. I see no strong efforts to avoid extreme AGW and suspect humanity to be too shortsighted and comfortable with it's illusions to do the minimum necessary. An extreme thermal maximum, unrelated to orbital cycles or solar ones will leave a lasting legacy, if not on the climate of the far future, on it's biology, so I stand by 'irrevocably changed'.
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  18. #17  
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    Yes, the Arctodus simus (Cope), Smilodon fatalis (Leidy), and Canis dirus (Leidy), are all gone.
    I'm sorry, my responses are limited. You must ask the right question.

    "The track of a glacier is as unmistakable as that of a man or a bear, and is as significant and trustworthy as any other legible inscription"
    John Strong Newberry; 1873

    "From observations upon living glaciers, and from the known nature of ice, we may learn to recognize the track of a glacier as readily and unmistakably as we would the familiar foot-prints of an animal." G. F. Wright 1891 (108-109)

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    We are in the middle of the Pleistocene, which has been going on now for about 2.5 million years, give or take. Its cause is not 100% certain, but 90% is good enough to use with confidence. Keep in mind that the earth's climate is always trying to keep itself in equilibrium, and some minor changes can make long term changes in climate conditions.

    For example prior to the time mentioned above, ice ages had become practically non-existent. But one singular event led to this. And keep in mind that free flow of oceans from the equator to the northern limits distribute warm temperatures there, keeping the planet warm. if those waters are shut down, or even slowed down, this will lead to a cooling effect in the earth's climate temperatures.

    Now, one thing prior to 3 million years in the past, North and South America were separated from each other. But moving plates allowed the two to join, forming the Isthmus of Panama. This doesn't look to be much, but it shut off the free flow of waters from Pacific and Atlantic oceans. And because of this it stifled the free flow of warmer Pacific currents into the North Atlantic, and as they say, the rest is history.

    Add to that the Milankovitch Cycles and the cosmos added to the input of climate. This has resulted in a steady series of approximately one hundred thousand year glaciations, followed by short/brief interglacials, one of which we are at the tail end of right now. That's right, we are headed back into another round of the Pleistocene, and no amount of 'so called' man-made global warming is going to halt it. Only the opening of the two oceans once again, will halt this current Pleistocene.

    But here is something else that also enters into the equation, other than land bridges and celestial positioning. Think Impactors. if you view any chart of the Lake Vostok data, you can see rapid/sharp ups and downs of the global temperatures. Guess what most likely causes these. If you say Impactors, YOU WIN!! Probably anyway. My guess is that the planet starts cooling down, and is holding itself on the cliff, as the planet repositions celestially. And then BAM some comet or asteroid does its thing, and the world climate is suddenly thrown off the precarious perch it is sitting, and into the cold abyss. But that is just a well informed guess.

    let's see if I can find a Vostok chart.

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    Hmmm, middle of the Pleistocene? That is an interesting suggestion, and one I have not seen before. Reference?

    There have not been any major impacts since the K-T boundary. The cause of the last ice house is due to planetary position and mountain building changing the global weather and ocean currents.
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    Would not take very big glacier to immobilize typical city in high latitude. Just a few feet of ice.
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    Define immobilize. Even just a couple of feet of ice would be enough to raze most of the city. Of course the average speed of motion for a glacier is in the inches to maybe 10s of feet a year so its not like there would be no warning before it got to a city.
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

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    Quote Originally Posted by John L View Post
    But here is something else that also enters into the equation, other than land bridges and celestial positioning. Think Impactors. if you view any chart of the Lake Vostok data, you can see rapid/sharp ups and downs of the global temperatures. Guess what most likely causes these. If you say Impactors, YOU WIN!! Probably anyway. My guess is that the planet starts cooling down, and is holding itself on the cliff, as the planet repositions celestially. And then BAM some comet or asteroid does its thing, and the world climate is suddenly thrown off the precarious perch it is sitting, and into the cold abyss. But that is just a well informed guess.
    My Bold

    Probably not. The last big hit was Meteor Crater, 50Kya, the impact of the impact was entirely local. There is an unproven theory for the Younger Dryas, Firestone, et. al., but it is more likely to have been caused by a freshwater injection to the North Atlantic.

    Also, it will probably be twenty, thirty, or forty millenia until the next glaciation. These things do not work on human time scales generally, but, again, the Younger Dryas onset, and particularily, its end, could be seen as generational events, where stories could have been handed down of how things were in their recent past; i.e./ grandfathers time, maybe.
    I'm sorry, my responses are limited. You must ask the right question.

    "The track of a glacier is as unmistakable as that of a man or a bear, and is as significant and trustworthy as any other legible inscription"
    John Strong Newberry; 1873

    "From observations upon living glaciers, and from the known nature of ice, we may learn to recognize the track of a glacier as readily and unmistakably as we would the familiar foot-prints of an animal." G. F. Wright 1891 (108-109)

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  24. #23  
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    if you look at the pattern over the last few 100,000 years it would appear that coming out of an ice age happens fairly sharpish, whereas descending in one happens in stops and starts and many reversals, but with an overall downward trend

    also, there have been sharp downturns which are thought to be related to currents in the north atlantic, with (as far as i'm aware) no impact scenarios being involved

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