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Mick Harper
Site Admin
In: London
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| It is classified as igneous, and is supposed to make up most of the ocean floor. |
Two odd things here.
1. You said it was basaltic. Now you are saying it is igneous. I assume one category includes the other but they are not the same thing.
2. You said "Oceanic crust is basaltic" without equivocation. You cannot now say "is supposed to be". Either you believe them in which case your statement stands, or you are doubtful in which case you must tell us of your doubts.
You are of course quite entitled to assume that ocean floor is basaltic for the purposes of argument but you must not say it as though it were observable fact. You have to remember that we are mostly duffers in these kinds of things so we need to know what is true and what is mere orthodoxy.
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| Mick Harper wrote: | | in a cycle of 41,000 years |
Kindly explain how anybody knows this. Cycles, as you may or may not know, are an AE staple. We are highly sceptical of any that have not actually been lived through (and even then they turn out to be bollocks eg the trade cycle).
And by the way, AEists, everybody's waiting for El Nino at the moment (mainly to break the Californian drought) so I expect it will turn up any day now.. |
Fracastoro, apparently, was the first to realise that the obliquity is decreasing at a fairly constant rate during historic time...the Ancient Greeks, and maybe the Chinese could measure obliquity, but basically it is Milankovitch who constructed the cycle.
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Mick Harper
Site Admin
In: London
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Just as I thought. There is no cycle here, merely an observed movement that (for no obvious reason unless you can provide one) has been declared to be cyclical.
There is however a reason why people like to construct cycles (whether there is one or not) and it is called technically Uniformitarianism or more colloquially "human beings like things not to change but when things do change they like to know the reason for the change so when they observe a change which they don't know the cause of they declare it to be a cycle ie there's no change".
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| Mick Harper wrote: | | It is classified as igneous, and is supposed to make up most of the ocean floor. |
Two odd things here.
1. You said it was basaltic. Now you are saying it is igneous. I assume one category includes the other but they are not the same thing.
2. You said "Oceanic crust is basaltic" without equivocation. You cannot now say "is supposed to be". Either you believe them in which case your statement stands, or you are doubtful in which case you must tell us of your doubts.
You are of course quite entitled to assume that ocean floor is basaltic for the purposes of argument but you must not say it as though it were observable fact. You have to remember that we are mostly duffers in these kinds of things so we need to know what is true and what is mere orthodoxy. |
I'm certainly a duffer so I'm glad most of your posters share this quality!
1) Just as a lay person who reads some earth science material in books or on the Web I understand Basalt to be a kind of igneous rock.
2) Scientists will have arrived at the theory that most of the oceanic floor is Basalt from drilling and other forms of sampling. However all that we can know is that from the sample areas tested the majority of the rock is Basalt. As with any theory they have then extrapolated this to conclude that most of the ocean floor is similar. To me, that seems reasonable and I have no grounds for scepticism. On the other hand Continental Drift was once considered cranky and is now part of the orthodoxy
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| Mick Harper wrote: | Just as I thought. There is no cycle here, merely an observed movement that (for no obvious reason unless you can provide one) has been declared to be cyclical.
There is however a reason why people like to construct cycles (whether there is one or not) and it is called technically Uniformitarianism or more colloquially "human beings like things not to change but when things do change they like to know the reason for the change so when they observe a change which they don't know the cause of they declare it to be a cycle ie there's no change". |
Well whether or not there is a cycle there has at least been an observable change in the tilt so I come back to my original question: would this be enough, together with the centrifugal bulging, be enough to explain the inundation of certain areas of the Earth's crust?
And again, isn't the melting of the Scandinavian Ice Cap and Laurentian one a simpler way of explaining rising sea levels? Is that not a more Occam explanation?
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Mick Harper
Site Admin
In: London
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If you satisfied that these test drillings are kosher so am I.. The ocean floor is henceforth mainly basalt.
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Mick Harper
Site Admin
In: London
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If the change does not need to be cyclical then I withdraw that objection. But just to make sure we are roughly on the same page, when you say that it is observable that the tilt varies from 22.1 to 24.5 degrees would you mind confirming who observed a) the 22.1 and b) the 24.5.
| And again, isn't the melting of the Scandinavian Ice Cap and Laurentian one a simpler way of explaining rising sea levels? Is that not a more Occam explanation? |
Yes indeed. So long as a) you can confirm that sea-level has risen b) that it rose at the same time as the melting of those two ice caps and c) that the amount of ice in b) is roughly equivalent to a). Good luck with that.
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| Mick Harper wrote: | If the change does not need to be cyclical then I withdraw that objection. But just to make sure we are roughly on the same page, when you say that it is observable that the tilt varies from 22.1 to 24.5 degrees would you mind confirming who observed a) the 22.1 and b) the 24.5.
| And again, isn't the melting of the Scandinavian Ice Cap and Laurentian one a simpler way of explaining rising sea levels? Is that not a more Occam explanation? |
Yes indeed. So long as a) you can confirm that sea-level has risen b) that it rose at the same time as the melting of those two ice caps and c) that the amount of ice in b) is roughly equivalent to a). Good luck with that. |
There's a lot of meat on that but I am going to disappoint on both. Let's take the tilt first. Unfortunately I do not have the primary sources (specific scientific papers) at my disposal (I don't subscribe) so I am reliant on secondary ones which sometimes don't mention them.
The Geophysical Institute of the University of Alaska states that 10,000 years ago it was 24 degs 15 mins. It is now 23 degrees 4 mins. It gives another figure for the coldest part of the Ice Age.
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Mick Harper
Site Admin
In: London
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Unfortunately I do not have the primary sources (specific scientific papers) at my disposal (I don't subscribe) so I am reliant on secondary ones which sometimes don't mention them.
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Look, Aurelius, I know I'm giving you a hard time but this won't do. We're dealing here with (I had assumed) basic 'facts'. It should be on Wiki! Nobody gives a monkeys about who first established it (your primary source presumably) but you say you are familiar with secondary ones. Some of them mention it, you say, OK, let's be having 'em. One is plenty. Wiki even -- then we can be the judge.
| The Geophysical Institute of the University of Alaska states that 10,000 years ago it was 24 degs 15 mins. |
Do you really mean 'states' or do you mean somebody once wrote a paper claiming that magnetic rock striations would appear to be consistent with ... etc etc
| It is now 23 degrees 4 mins |
OK, that's one degree in 10,000 years -- if the 24.15 figure is to be believed. That leaves the low figure (22.1) and the high figure (24.5) unaccounted for.
| It gives another figure for the coldest part of the Ice Age. |
Surely then this date must correspond with the melting of the Scandinavian and Laurentian ice caps. But you say it's different!
Just by the by, you'll probably find that because we know when these two ice sheets disappeared (10,000 years ago) everybody is feeding that figure into their models, juggling the numbers and when three lemons come up they write the paper. Just saying. From experience. These people are intellectual crooks. Though terribly nice in every other way.
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| Mick Harper wrote: | If the change does not need to be cyclical then I withdraw that objection. But just to make sure we are roughly on the same page, when you say that it is observable that the tilt varies from 22.1 to 24.5 degrees would you mind confirming who observed a) the 22.1 and b) the 24.5.
| And again, isn't the melting of the Scandinavian Ice Cap and Laurentian one a simpler way of explaining rising sea levels? Is that not a more Occam explanation? |
Yes indeed. So long as a) you can confirm that sea-level has risen b) that it rose at the same time as the melting of those two ice caps and c) that the amount of ice in b) is roughly equivalent to a). Good luck with that. |
I am confident that the global sea level has risen since 10,000 years ago, in fits and starts. Since 1850 it has been measurable by tide gauges and human observation. Before that it is much more difficult; drowned forests, the archaeology now being found at the bottom of the North Sea, the salination of the Black Sea, even the amount of continental shelf under water are suggestive.
However one could certainly argue that locally at least some of these changes could be the result of land sinking rather than sea rising.
I wondered how scientists determined when ice sheets melted and apparently it is done by radiocarbon and surface exposure dating.
I accept this is not a watertight defence!
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| Mick Harper wrote: | Unfortunately I do not have the primary sources (specific scientific papers) at my disposal (I don't subscribe) so I am reliant on secondary ones which sometimes don't mention them.
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Look, Aurelius, I know I'm giving you a hard time but this won't do. We're dealing here with (I had assumed) basic 'facts'. It should be on Wiki! Nobody gives a monkeys about who first established it (your primary source presumably) but you say you are familiar with secondary ones. Some of them mention it, you say, OK, let's be having 'em. One is plenty. Wiki even -- then we can be the judge.
| The Geophysical Institute of the University of Alaska states that 10,000 years ago it was 24 degs 15 mins. |
Do you really mean 'states' or do you mean somebody once wrote a paper claiming that magnetic rock striations would appear to be consistent with ... etc etc
| It is now 23 degrees 4 mins |
OK, that's one degree in 10,000 years -- if the 24.15 figure is to be believed. That leaves the low figure (22.1) and the high figure (24.5) unaccounted for.
| It gives another figure for the coldest part of the Ice Age. |
Surely then this date must correspond with the melting of the Scandinavian and Laurentian ice caps. But you say it's different!
Just by the by, you'll probably find that because we know when these two ice sheets disappeared (10,000 years ago) everybody is feeding that figure into their models, juggling the numbers and when three lemons come up they write the paper. Just saying. From experience. These people are intellectual crooks. Though terribly nice in every other way. |
Wiki says
For the past 5 million years, Earth's obliquity has varied between 22° 02' 33" and 24° 30' 16", with a mean period of 41,040 years. This cycle is a combination of precession and the largest term in the motion of the ecliptic
But I haven't been able to find out where they get the extremes from. Perhaps someone else who posts has a better idea?
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Mick Harper
Site Admin
In: London
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| I am confident that the global sea level has risen since 10,000 years ago, in fits and starts. Since 1850 it has been measurable by tide gauges and human observation. |
So ... global warming has been happening for 10,000 years and we've been measuring it for 150 years. That should take the sails out of those global warming johnies.
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Boreades
In: finity and beyond
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| aurelius wrote: | For the past 5 million years, Earth's obliquity has varied between 22° 02' 33" and 24° 30' 16", with a mean period of 41,040 years. This cycle is a combination of precession and the largest term in the motion of the ecliptic
But I haven't been able to find out where they get the extremes from. Perhaps someone else who posts has a better idea? |
I'm sure I've done that, and I thought I'd done that here, in a different context, of how people would know where "True North" was c.5,000 years ago.
The trouble is I can't find the topic. It's not AEL's fault, it's because we're all using "last generation" forum software which generically lacks the facilities for contextual tagging of content, or even simple keywords.
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Mick Harper
Site Admin
In: London
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Generally I agree but members should be warned that for reasons our software masters can never satisfactorily explain the default setting for the Search engine is Topic which is no use at all. You can click Posts if you want to know exactly where something is.
If you post your thoughts all over again, Borry, you might find you've changed your mind in the meantime. This is, I would have thought, something we need to revisit.
PS Is 5,000 years ago very useful?
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Boreades
In: finity and beyond
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The notion of posting my thoughts all over again is troubling me. I don't think it's the possibility I would be arguing with myself, it's more the "early onset dementia" angle that's giving me anxiety. Did I say that? Where did I say it? I can't find where I said it. Is this the right forum?
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