So you concede that your original statement that "most mountains are formed through volcanic or molten lava activities" was incorrect. Excellent. At last we are making progress.
Did my incorrect statement that "a hot pool of lava underneath" cause the confusion? Apparently this was a big error on my part to say, but I later posted that it was a trivial argument: magma is called lava only when it is on the surface, but minerolagically there is basically no big difference to argue over. All mountains are produced by convergent, divergent, or transform boundaries of tectonic plates OR by volcanoes that erupt within plates that form volcanic arcs or small mountains. All of these processes involve the transformation of igneous rock into molten magma that deforms the tectonic plates to create mountains. Am I stating anything incorrect here?
No, your statement that "most mountains are formed through volcanic or molten lava activities in plate tectonic divergences or convergences" caused the confusion. I maintain that this is not correct. I think that's basically fair to say, except that volcanic arcs are a consequence of subduction rather than intraplate volcanism. It is this that I have an issue with. I assume you meant that the igneous rocks are formed by the magma? Or did you mean that magma is formed by the melting of pre-existing igneous rock? Either way, to say that magmatic activity occurs during orogeny is not the same as saying that magmatic activity is responsible for the orogeny. The mountain building is accomplished through folding and reverse faulting.
Lava is molten magma extruded through volcanic activity and igneous rock is made from solidified molten magma. Ninety-five percent of the Earth's crust and lithosphere are composed of igneous rock down far below 200 km.; therefore, 95% of the Earth's crust came fom molten magma (and some impurities). Every major mountain chain in the world was made through tectonic plate activities, magma plumes, or a hot spot - like in dome mountains - AND are composed of volcanoes, and have been partially or entirely built by volcanoes, or the magma underneath moving the tectonic plates. The Andes, Appalachians, Alpides, Cascades, Himalayas, Rockies, the Mid-Atlantic Mountain Range, and every orogeny range formed throughout the history of the Earth are or were composed of volcanoes. Molten magma formed all these mountains both from below through tectonic plate convergence, subduction, divergence, or transform faults, and from above by volcanic activity. The only exception that I can think of are dome mountains: they are short and wide and formed by uplifts due to a plume or a hot spot. Heck, even a volcano itself is a mountain formed entirely by its own volcanic activity.
Not volcanoes and dome mountains. Volcanoes are mountains formed entirely by layering: dome mountains can be uplifted without folding.
Valich, surely you don't mean to extend your use of the terms "volcanic or molten lava activities" to include the mantle convection responsible for plate tectonics? I wouldn't have expected somebody who has "been teaching for over ten years after twenty years of higher education" to fall prey to one the most common misconceptions about the mantle. Magma is molten rock. The mantle is not molten rock. Plate tectonics is not a volcanic or molten lava activity.
Please do not requote my term "molten lava activities" again as I have corrected that very trivial mistake three times already! Get it? It was an extremely "trivial" error written in haste. I am not submitting a scientific paper for publication in a journal here: this is a "forum." I quote from three dictionaries: "Magma is molten rock material from which igneous rocks is formed." McGraw-Hill Dictionary of Earth Science "Magma: Naturally occurring molten rock material" Dictionary of Geological Terms, prepared by The American Geological Institute. "Magma: A molten fluid, formed within the crust or upper mantle of the Earth." Dictionary of Geology, D.G.A. Whitten, Penguin Reference. Do you know what causes plate tectonic movements? Tectonics revolutionized the geographic stratum of the Earth into a smaller outer crust, a tectonic plate within the lithosphere, and an underlying asthenosphere (a portion in the upper mantle that is even more fluid than the upper lying lithosphere). The lower you go, the more plastic and fluid it gets with convection currents that recirculate the upper crust that is subducted through plate tectonics. Finally when you reach the outer core of the Earth it is a completely liquid structure, with a center solid core made up mostly of iron and a bit of nickel. This outer core circulating around the Earth's solid inner core is what gives the Earth's its magnetic field, including the North-South pole magnetism. The lower you go down into the Earth, the hotter it gets, until you reach the solid iron center core which cannot be melted any further than the liquid magma igneous rock chemical compositions above it: basalts, dolerite, gabbro, granite, pyrclastic rocks, rhyolie, serpentine, trachyte, and pneumatolysed liquified rocks.
As usual, you misquote my original posting to satisfy your egotistic self-satisfying needs, right? Truth in kowledge has no place for this. Now that I look back, I see that I originally posted: "Most mountains are formed through volcanic or molten lava activities in plate tectonic divergences or convergences." And I corrected my trivial error. Damn! Please contribute to the educational advancement of this forum: it is called "Sciforum: the intellegent comunity."
Valich, I am not picking at your substitution of lava with magma. In truth, I read it as "most mountains are formed through volcanic or molten magma activities" anyway. But this still doesn't make it correct. I said: You said: Great. No arguments there. However, you still claim something which I don't think is just a trivial mistake. You said (with my boldface): If you mean to extend 'molten lava/magma activities' to incorporate mantle circulation, and thus tenuously support your claim that "most mountains are formed through volcanic or molten lava activities in plate tectonic divergences or convergences", then you are in error. The mantle is solid (a plastic solid - granted). Even at ocean ridge axes there is only partial melting of mantle material. This is why the ocean crust is basaltic in composition compared to the mantle, which is peridotite. The magma produced behind subduction zones is a result of water being introduced into the mantle by the subducting plate. This lowers the melting point of the rock, causing partial melting to occur in a process called anatexis. Ophiolite, correct me if I'm wrong. With that moniker I'm sure you know it in far greater detail than myself! Valich, please understand that although I have quoted you several times in this post, I am not focussing on your magma/lava typo. I just think there's a more fundamental error within your posts.
Laika, you are correct in your summary and in your concerns over his fundamental errors. I have given up on Vallich several times. I do not know whether he is thick, mentally compromised, deliberately provocative or what. Frankly I would stop posting anything in response to his posts except that he is so often so wrong that I worry that casual readers are going to be misled by his misinformation and misinterpretations. My degree is in geology and though I only worked as a geologist for a brief period I have retained a close association with aspects of geology through my work (specifically drilling technology, wherein the mechanical properties of rock are of prime importance) and through reading. I get quite emotional when I see facts and theories being distorted as vallich has done. Several posters of long standing have taken him to task on several threads for the same kind of thing. He simply refuses to acknowledge his errors, attacks the individual, pours out a mass of jargon and multiple references that have relevance only because they contain some of the same words, sewing confusion in his wake. The best thing might be just to ignore him. (Alternatively, I am considering using it as an opportunity to see if their is anything in the use of voodoo dolls to extract vengance at a distance. You will recognise that as a joke, Vallich will see it as evidence of my mental problems.)
The mantle is solid? And then you say it is "plastic"? Basalt is the Earth's crust's (lithosphere) most uncompassing solidified magma. "Water being introduced into the mantle by the subducting plate"? Cite your sources please! Fluidity is not equivallent to water, let alone magma or metamorphism. You're implying that the ocean crust is basaltic because it is in the ocean, under water? And that this is not part of the Earth's mantle?
Always this, "and my degree in geology...blah, blah,blah" as if this means jack. You've been so wrong so many times in your posts, espectially regarding "dome mountains" that you by all ethical standards should render your degree back to whatever institute granted it to you! You, and whoever you are referring to, have continuously refused to acknowledge any and all of my factual scientific citations, instead relying on your own subjective interpretations without ANY facts.
Yes, these two terms are not mutually exclusive. To say that the rocks in the mantle are plastic is to say that they undergo plastic (permanent) deformation when stressed. All solids undergo varying degrees of elastic, plastic and brittle deformation, depending on the type of solid, confining pressure, temperature and strain rate. The mantle is a plastic solid. I'm not sure what you mean by this. The term lithosphere refers to a structural rather than compositional unit. The Earth's lithosphere is the rigid outer part of the Earth. It is composed not only of ocean floor basalt, but also more felsic continental rocks, and even incorporates huge thicknesses (up to dozens of kilometres) of ultramafic mantle rocks that have been underplated. The mantle consists mostly of peridotite (magnesium and iron silicate). This has a very high melting point. Therefore, when partial melting occurs due to rifting or a hot spot plume, the resulting melt contains a disproportionate volume of minerals with lower melting points, that are more easily included in the magma. This is why rocks of basaltic composition do not reflect the composition of the mantle, but are relatively enriched in pyroxenes and feldspars. This is why the ocean crust is basaltic. Between being formed at a spreading axis, and being subducted some millions of years later, the ocean lithosphere has plenty of time for hydrothermal alteration. Water is incorporated into the structures of some minerals, hydrating and changing them. When these are subducted the volatiles released lower the melting point of the surrounding rocks. If the melting point is lowered to below that of their current temperature, partial melting will occur. This is called ANATEXIS, and will be in one of your many books on the subject. The composition of the melt can be further modified by the process of fractionation and differential crystallisation as the molten material accumulates. This is why intrusions and eruptions in a continental setting generally involve more silica-rich material. Quartz has a low melting point compared to the other components which may have started in the melt, but which then crystallised out in an unexposed chamber. The ocean crust is derived from, but is not part of, the Earth's mantle.
Excellent. Volcanic arcs are definitely formed by subduction and not "intraplate" volcanism. Plate tectonic convergences can lead to subduction, transformation boundies, or a direct confrontation of the converging plates.
I never said that the mantle was solid? When a plate is subducted it is a subducted solid plate. Current theory is that there are circulating convection currents in the mantle that circulate parts of subducted plates within the mantle. The lithosphere is composed of both the plates, countless compositional minerals, "mantle rock that has been underplated," and the magma that moves them. Again, as you yourself know, are you referring to what is considered the physical or chemical composition categorizing of the mantle? The ocean crust is mostly basaltic. The crust is much thinner in the ocean than the much larger crust on the continents that consist of much much more sedimentary rock. The majority of the upper crust on continents is not basaltic. Yes! Yes! Yes! Not all plate boundaries, subductions, and intraplate fissure have a straight axis. This is one problem why the creation of the Hawaiian Island volcanic region is still not fully explained. There is a dual-degree intraplate fissure that developed alongside a pre-existing ridge that is yet unexplained. The Pacific Plate moves over an underlying hotspot here. Keep up your research. When are you going to write a book?
As for other types of mountains--and again using New Zealand as an example because I know it so well--here's the current state of play so far as geological knowledge about NZ. The Pacific Plate is pivoting anti-clockwise, with the axis of rotation centred at about 60 degrees southern latitude and on the International dateline. That means that the full force of the plate's rotation is swinging due west (ie at a 90 degree angle) directly at the Australian Plate, on which the western part of the North Island sits. This collision affects the southern half of the east coast of the North Island. This creates successive ranges of hills by compression, because as the Pacific Plate is subducted under the North Island, sea-floor material is scraped off, piled up and hardened into rock by compression. Inland of the coastal ranges, the descent of the plate into the mantle is creating tension, which is stretching and thinning the crust. This has created the Taupo Volcanic Zone (TVZ) where all of New Zealand's largest volcanos ore situated presently. This is the current geological axis of New Zealand, i.e. where the most intense volcanic activity is going on. Further down, in the South Island, the angle where the Australian Plate meets the Pacific Plate is much more oblique; the action is a sliding motion rather than a head-to-head impact as further north. The result is a slip-strike earthquake zone, the Great Alpine Fault, which runs all the way down through the South Island. Occasionally (periodicity being 250-400 years) there are vast earthquakes on this faultline. 30mm of strain builds up in a year on this fault, and the last time there was a major tremor there was about 1720 AD. So the 250-year danger-zone was entered in about 1970. Any time from now on, going by past geological evidence at least, we can expect another major earthquake on the Alpine Fault. The Southern Alps, along the western edge of the South Island, are caused by the compressive forces of the Australian Plate's impact with the Pacific Plate. New Zealand was once attached to Australia, but broke away millions of years ago (how many slips my mind just now--I think about 55 mya). Anyway, New Zealand was once much larger than it is presently--at the time it broke away it was a continent about half the size of Australia. As the Tasman Sea widened between NZ and Oz, the continental crust of New Zealand was stretched and thinned. Plus of course erosion did its work. The result is that now New Zealand's former continent is mostly underwater.
I know you have been following this thread, so you must of read what I replied to Xylenes's post, to which HE replied: "The Northland region is mostly plain, fairly low-set by New Zealand standards, i.e. below 600 ft a.s.l. The trench into which the sediment fell was quite deep, several thousand feet, so there's a long sedimentary column. The scene is complicated by comparitively recent volcanism, which occurred between about 20 million (west coast) and 3 millon years ago (east coast). Apart from that volcanic activity, everything else is sedimentary. It's a mountain in reverse, if you like--an upside down mountain range." I thanked him graciously for this revelation and told him that I am anxious to learn more, but do not have the time to research it right now. Can you combine your explanation with his to make the two more understandable together? The Cascade Mountain Region is similarly confusing to me. The simplest explanation only refers to the subduction of the Juan de Fuca Plate but the formation of the entire range includes climatic shifts, the surrounding basalt ranges, the Columbian Basin, and the consequent "circular activity" in the upper crust?
Well, it means a fucking lot to me weasel, since I adore geology and the concepts and the theories and the paradigms. I am delighted to have such limited understanding as I do have on the subject and it offends me when a cretin such as you[rself distorts, misinterprets and plain lies. I mentioned my degree on this occasion because it was a relevant reply to Laika's post. Cite a single example. Your factual citations are consistently either irrelevant, misinterpreted or misapplied. You have revealed consistently that you have no understanding of the material you are quoting. Please piss off.
Typical words from the "toilet mouth." As I said to your elementary associates: I have posted the most excepted explanations within the scientific community as they are writen in almost all - maybe all - biology textbooks, and as they are supported in most scientific journals. Who are you guys? Paleontologists? Geologists? Scientists? No! You guys are Sciforum fanatics who browse the web like pinball wizards and excell in condemning other people who proclaim to know more knowledge than you then just cut them down (do I detect jealousy?). How immature and unscientific. This forum is called "Sciforum - the Intelligent Community." The first step to be part of it should be to use the scientific method, but instead your first step is to condemn others and resort to being a "toilet mouth," rather than responding to ideas in a respectable scientific way. GET A LIFE!
