Essential dynamics & mechanisms of sea-level fluctuations

Let's carry over our discussions from the other thread http://EvC Forum: Crand Canyon Tracks Were Not Formed During a Worldwide Flood -->EvC Forum: Crand Canyon Tracks Were Not Formed During a Worldwide Flood to here.Let's get to the bottom of what caused the sea-level fluctuations of about 2000 feet during the deposition of the geological column.We have two primary sources of sea-level fluctuation:
* tectonics
* glaciationWe are mainly talking about the 10-100 million year (mainstream framework) cycles of the sea-level curves known as '2nd order' curves which are presumably primarily tectonic.My mainstream reading suggests that, yes, sea-floor spreading and suduction changed the ocean basin volumes and led to sea-level fluctuaions of about 2000 feet. It seems this was would have to be primarily due to variations in spreading rates and/or subduction rates. I am currenlty tracking down a ref I saw suggesting that spreading rates may have been constant although that is not the present consensus. I wonder whether then it was variable subduction rates that led to the cycles. In any case it seems to me these are the fundamental potential mechanisms.Here is an excellent mainstream summary of sea-level change mechanisms: http://rmocfis.uprm.edu/~morelock/eustatic.htm[This message has been edited by Tranquility Base, 10-21-2002]

wj (answer to your post in the other thread)See my 'EDIT' to Edge as well as Moose's coment. I have mixed up the terms for trench and rift valley/ridge!All I am syaing is that the bulging at the ridges would generate sea-level increases if this bulging were variable. We empirically know that sea-levels have risen and fallen and so it is natural to ascribe these long-term fluctuaitons to such tectonic effects. This is agreed mainstream. I am simply trying to tease out the essential dynamics.

^ I sure do. But if you're proposing that we systematically discuss sea-level fluctuations in a thread where I grandstanded an individual tectonics simulator then you must have a considerably more generic view on what constitutes a new thread! I prefer more focussed threads.PS - Your link would work better if you inserted a html reference in addition to a caption.[This message has been edited by Tranquility Base, 10-21-2002]

EdgeSince I kept talking about spreading from trenches I would have thought someone else would have picked up my misuse of terminology! The bulging I am talking about is the well known bulging either side of the rift valleys.I'm not saying any of this prove the flood etc. I just like to be clear baout what's going on.Some form of runaway subduciton and/or radioheating is still conceivable as demonstrated by Baumgardner's simulations.[This message has been edited by Tranquility Base, 10-22-2002]

JoeI never claimed that the bluges at the spreading centres were novel, I was just trying to clarify that that was a major mechanism for sea-level change. What I was wondering about was variable subduction rates which there seems to be little comment on in my readings.I'm used to being misunderstood in my job too because I have to converse with real biologists all the time when I'm actually a (bio)-physicist. I enjoy learing the new stuff and the associated terminologies but occasionaly make stuff-ups despite having valid points to make.The point I was trying to make is a valid one. And I haven't even got to state it yet properly! Here it is: What is the evidence against variable subduction rates being resposible for sea-level fluctuations?

Why is it that you think the tectonic changes were always so slow?1. They're slow now
2. You presume that sediments alwyas collect at today's rates
3. You assume that radioisotopic decay has been constantWhile I'll grant number 3 as being on a stong footing, number 2 a priori assumes no flood so it can't be used as evidence and number 1 similarly assumes uniformitarianism.So we're really down to radiodating. Apart from radiodecay there are no real reasons that these processes couldn't have happened much more quickly than you assume. And on the radiodecay front we have evidence of excess helium retention suggesting accelerated decay.For us of course we even have the Bible telling us in plain language that the doubters will 'willing forget' that the flood occurred.I completely understand your point of view. If there was no flood, no accelerated decay then of course it happened over millions of years. We're simply sharing an alternative way of looking at it that is unashamedly Bible inspired.

JoeYou said: Why do you insist on a caricature of science rather than a real view?Why do you insist on caricaturing me as if my entire being and thoughts can be summed up by one line in a post?Is it possible that I was referring to global tectonics? That was the context. I know all about the Alaska event. On many of the occasions that you accuse me of not knowing something I actually know it.You have made good points about predicted bathymetry. I some how doubt it is as clear cut as you suggest, however I am way out of my field and my readings here.My statement that mainstream geologists assume slow sedimentation rates is a very accurate generalizaiton.

^ I'm talking about anyone taking a look at any arbitary local wall of strata. It will be assumed to have been formed slowly.