For Faith: Divergent Boundaries

http://www2.nature.nps.gov/...ogy/usgsnps/pltec/diverge.htmlLots of good condensed information. The main point: Earth Floor: Plate TectonicsAnother good brief treatment of divergent boundaries.http://pubs.usgs.gov/publications/text/understanding.htmlGood treatment of all of the type of boundaries.As unfortunate as it was I was able find some places that claimed that the ridge was pushing the other plates apart. Some sites described the magma upwelling as "pushing up".The point is that the "pushing" being described on these sites has to do with the tectonic theory of convection cells and is not the same as the compression that happens at a convergent boundary. If you believe in convection cells or not the raw observations have divergent boundaries which are pulling apart, and convergent boundaries which are pushing against each other.The Appalachians were build by the Appalachian Orogeny which is explicitly a convergent process.Orogeny - WikipediaThese are the facts. Now you may use these facts in order to construct your theory about the formation of the folded strata in IRH's thread. I don't know why this has turned into such a big deal. What does it matter if this all explaining flood created a mountain range first and then split the continents? No where in any of my objections did I say anything about the speed that this had to occur in your explanations just the order of events. The order of events are factual. I put this in Links and Information because there is no debate topic here. These are the facts. Now use them in your theory, presumtions or not.

Hello jazz. You're giving me a lot of work to do it seems. You aren't really explaining it, you are requiring me to research it. I don't know how convection acts. I said I've already done a lot of research on it so please provide a better explanation in your own words -- and avoid terms like "convection" -- or at least define them clearly. I need explicit explanation. Diagrams would be handy instead of a lot of links I'm going to have to decipher myself. I'm tired and coming down with a cold too. Thanks.Also, I proposed a thread for this purpose in PNT already.I also just now answered you on the same topic on the IRH thread about Geology Data.This message has been edited by Faith, 09-14-2005 10:00 PM

Realized this thread is not for debate. So I moved the post and included it with my OP on the PNT forum, where I propose a thread to follow up on the YEC approaches thread, but then it appears that Jazz had already read it and answered it so now I'm going to put it back although it is off topic.==================
I looked at your first link since you weren't showing up to respond, and found this animation of the movement at the continental ridgeNow this animation is EXACTLY what I've been visualizing. It is clearly PUSHING magma to left and right. Perhaps we are having a terminological problem here. Please explicitly explain how my description of the movement on that animation as pushing is wrong.All the following is what I already learned from my own researches, and "pushing" is consistent with it all. Picture a vertical model of the same action, a set of double pocket doors that slide open from the center where they meet. You insert your hands to slide them apart. That is PUSHING them apart. You could stand in such a position that the exertion of your hand would be a pulling, but you wouldn't be in the center between the doors then, but on the side you are pulling toward. From the center the action is a pushing. If the doors were made of a material that could fold and ripple from that much pressure on them, they would.This message has been edited by Faith, 09-15-2005 01:23 AM

Very good observations Faith. Also some very good questions. If this goes much farther we might ask an admin to move this to a "real" forum.Here is where you have to be a little bit careful becuase many of the sites that talk about plate tectonics are also talking about convection cells.We cannot see convection cells. Convection cells are part of plate tectonic theory which proposes that plates are just these giant conveyor belts that continually turn crust into mantle back into crust etc. So in this sense there is no "pusher" or "puller". I didn't want to go there because I wanted to stick to just the facts, just the observations. Sure you can describe the divergent boundary as "pushing" if it is all part of a continuous sytem, but then you could also say a convergent boundary like a subduction zone "pulling" the rest of the crust under. The second description of "pulling" at a convergent boundary sounds much less appropriate but because of the whole "conveyer" idea of convection cells it is as legitimate as the "pushing" at a divergent boundary.So the term "pulling" or "pushing" in this sense may not have been appropriate because it refers to the theory rather than the straight observations. It is easy to say that the plates are "pulling" apart at the mid atlantic ridge when really the observation it is simply that the plate are moving in opposite directions. We can continue to call this "pulling" for convienence knowing that we are borrowing this term from the theory to help us describe the facts.Getting away from convection cells to the observations we can see, there is no dispute. At a rift the two halves are being torn apart. The primary evidence that shows this is formation of the rift valley, the faulting, and the magma rising.What happens to the crust when it is "pulled" apart it creates a void in the matter called a rift. Normally magma in the mantle cannot rise to the surface but the new void created allows it to rise to the surface which is why the is so much volcanic activity at divergent boundaries.Magma cannot "push" a plate simply because a liquid rising from the mantle is not going to displace hardened crust. When magma meets crust the magma goes up creating volcanoes.Last, there are two types of faults that occur in converget versus divergent boundaries. Reverse faults occur when compression causes one side of the fault to be pushed up onto the other. They are characterized by the upper most part of the structer hanging over the other. A normal fault is where one of the two halves slips lower than the other.Good pictures here:http://wrgis.wr.usgs.gov/docs/parks/deform/gfaults.htmlIf the crust was being "pushed" it would create reverse faults. Everwhere there are compressional structures such as anticline/syncline sequences there is also a lot of reverse faulting. With divergent action it is weakening the structure of the crust causing parts of it to fault and fall creating normal faults.The rift valley part of a divergent boundary is created entirely out of sequence upon sequence of normal faults causing the land around it to sink. Good examples of these can be seen in Africa and in the Rio Grande valley where I live.So forget about convection cells and the terminology therof. The rift systems we see today are full of normal faults, rift valley systems, and upwelling magma due to the space created by the plates moving apart. A convergent system is characterized by folding, reverse faults, and a different type of volcanism. The volcanoes along convergent boundaries are caused magma that rises to the surface because it has been heated due to the friction of the compression. These magma bodies will create explosive volcanoes like Mt. St. Helens due to their composition rather than the relativly calm volcanoes that occur in rift systems.Lots of info here. Please take your time. Does this answer you question?This message has been edited by Jazzns, 09-14-2005 10:39 PM

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