This
level-5 vital article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
this either does contains contradictions or seems to where it first says what volcanic arcs are, then says something like 'contrary to popular belief'...... Regardless, 'contrary to popular belief' whatever he says is weaselish, and i dont really know how to fix it because i am not educated on this subject.
After editing both of these articles today, it seems clear to me that this one should be merged into the other. All island arcs are volcanic arcs, so this article is just a subset of the other. There is already major overlap in content in the two articles, so this was an easy decision to make. Better to have one nicer, more comprehensive article than just leave these two as they are now. -- Seattle Skier (talk) 01:16, 13 April 2007 (UTC)
Should someone offer here geologists' explanations of why volcanic arcs or island arcs are arced? Geologist 13:02, 6 November 2007 (UTC)
The reason why Volcanic Island Arcs form an arc is due to the same physical properties that occurs in a river or a glacier. The zone of minimum resistance is in the centre of the flow and that not only includes the cross-section but the zone furthest from the bank. Look at a map of any volcanic arc and there is usually a transform system associated with the ends of the arc. The centre if the arc is where the pressure is at its greatest and the resistance to the forward motion is at a minimum. Just like a bow - as in bow and arrows. There is another feature that is useful to non-geologists and indeed anyone who wants to understand. The centre of the arc ) points to the subducting plate. The Caribbean Arc, South Sandwich Island arcs all point east - so the subducting plate is moving west. The volcanoes form above the descending plate where it attains a depth of about 100 km (60 miles) below the surface. There is more but it really does get rather technical. For the avoidance of any doubt I am "The Geologist" and not to be confused with the other person who signs their posts as "Geologist." The Geologist ( talk) 17:06, 3 February 2014 (UTC)
Volcanic arcs existed long before plate tectonics, and they will still be there if the theory is replaced. Perhaps the first sentence should not tie the arcs so intimately with one theory.
Ah. Thank you very much. That was very timely. However, I was thinking of something a little more drastic. :-)
Naturally I can't find my copy of Bucher's 'The Deformation of the Earth's Crust', in which Bucher distinguished descriptive statements about empirical objects from explanatory statements about theoretical objects. However, (we) scientific positivists do not especially believe science will ever explain those observable phenomena within its domain. We distinguish empirical objects (like volcanic arcs) from theoretical objects (like rising plutons). Theories connect the two. If an observation was used in developing a theory, the theory explains it. If the observation was not made before the theory, the theory predicted it. Even the most abstract objects of mathematical physics are scientific because they are tied to empirical observations by a string of currently accepted theories. The distinction is important. Blurring them confuses people and leads to the precipitation of 'creationists' and such.
Here's an example that distinguishes empirical objects from theoretical objects. Some facts I borrowed from Harold Jeffrey's 1959 'The Earth':--
Gutenberg, B. & C.F. Richter, 1949. The Seismicity of the Earth. Princeton: Princeton Univ. Press. ; Lake, P. 1931. Geographical J., v. 78, p. 149-160. ; Lake, P. 1931. Geological Mag., v. 68, p. 34-39. ; Scheidegger, A.E. & J.T. Wilson, 1950. Proc. Geol. Assoc. Canada. v. 3. p. 167-190. ; Wilson, J.T., 1951. Proc. Roy. Soc. Tasmania.
The above, of course, is a half-century out of date. Whether plate tectonics explains why volcanic arcs are arced, I have no idea. If not, the next theory may. :-)
Geologist ( talk) 04:41, 24 October 2009 (UTC)
How much of the clay in the continental rise is subducted with the basaltic slab is expected to vary with its dip, and is certainly not known to me. However, the sediments would be expected to lose fluids to the overriding mantle continuously. What relation has the decomposition of chlorite to the formation of calc-alkaline magmas? (Veins we see along chlorite-biotite isograds are not calc-alkaline.) The width of forearc basins, the dip of subducting slabs, the amount of clay subducted, and the composition of the overriding mantle all vary. Even if the positions of two phenomena could be correlated, correlation is not a cause & effect relation.
Unlike increasing temperature or pressure, increasing the amount of water does not increase its thermodynamic escaping tendency. The decomposition of chlorite will not suddenly produce calc-alkaline magmas; it could only increase their amount or change their mode (relative amounts of minerals).
Because of the above reasons for doubt, if there is a popular theory that chorite decomposition produces calc-alkaline magmas, could you make this very clear and give more references, by multiple authors? Thanks very much. (You may wish to keep in mind that theories of plutonism change every decade. This might be a current theory, a working hypothesis. or just the latest idea being explored. Geologist ( talk) 21:49, 23 October 2009 (UTC)
This
level-5 vital article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
this either does contains contradictions or seems to where it first says what volcanic arcs are, then says something like 'contrary to popular belief'...... Regardless, 'contrary to popular belief' whatever he says is weaselish, and i dont really know how to fix it because i am not educated on this subject.
After editing both of these articles today, it seems clear to me that this one should be merged into the other. All island arcs are volcanic arcs, so this article is just a subset of the other. There is already major overlap in content in the two articles, so this was an easy decision to make. Better to have one nicer, more comprehensive article than just leave these two as they are now. -- Seattle Skier (talk) 01:16, 13 April 2007 (UTC)
Should someone offer here geologists' explanations of why volcanic arcs or island arcs are arced? Geologist 13:02, 6 November 2007 (UTC)
The reason why Volcanic Island Arcs form an arc is due to the same physical properties that occurs in a river or a glacier. The zone of minimum resistance is in the centre of the flow and that not only includes the cross-section but the zone furthest from the bank. Look at a map of any volcanic arc and there is usually a transform system associated with the ends of the arc. The centre if the arc is where the pressure is at its greatest and the resistance to the forward motion is at a minimum. Just like a bow - as in bow and arrows. There is another feature that is useful to non-geologists and indeed anyone who wants to understand. The centre of the arc ) points to the subducting plate. The Caribbean Arc, South Sandwich Island arcs all point east - so the subducting plate is moving west. The volcanoes form above the descending plate where it attains a depth of about 100 km (60 miles) below the surface. There is more but it really does get rather technical. For the avoidance of any doubt I am "The Geologist" and not to be confused with the other person who signs their posts as "Geologist." The Geologist ( talk) 17:06, 3 February 2014 (UTC)
Volcanic arcs existed long before plate tectonics, and they will still be there if the theory is replaced. Perhaps the first sentence should not tie the arcs so intimately with one theory.
Ah. Thank you very much. That was very timely. However, I was thinking of something a little more drastic. :-)
Naturally I can't find my copy of Bucher's 'The Deformation of the Earth's Crust', in which Bucher distinguished descriptive statements about empirical objects from explanatory statements about theoretical objects. However, (we) scientific positivists do not especially believe science will ever explain those observable phenomena within its domain. We distinguish empirical objects (like volcanic arcs) from theoretical objects (like rising plutons). Theories connect the two. If an observation was used in developing a theory, the theory explains it. If the observation was not made before the theory, the theory predicted it. Even the most abstract objects of mathematical physics are scientific because they are tied to empirical observations by a string of currently accepted theories. The distinction is important. Blurring them confuses people and leads to the precipitation of 'creationists' and such.
Here's an example that distinguishes empirical objects from theoretical objects. Some facts I borrowed from Harold Jeffrey's 1959 'The Earth':--
Gutenberg, B. & C.F. Richter, 1949. The Seismicity of the Earth. Princeton: Princeton Univ. Press. ; Lake, P. 1931. Geographical J., v. 78, p. 149-160. ; Lake, P. 1931. Geological Mag., v. 68, p. 34-39. ; Scheidegger, A.E. & J.T. Wilson, 1950. Proc. Geol. Assoc. Canada. v. 3. p. 167-190. ; Wilson, J.T., 1951. Proc. Roy. Soc. Tasmania.
The above, of course, is a half-century out of date. Whether plate tectonics explains why volcanic arcs are arced, I have no idea. If not, the next theory may. :-)
Geologist ( talk) 04:41, 24 October 2009 (UTC)
How much of the clay in the continental rise is subducted with the basaltic slab is expected to vary with its dip, and is certainly not known to me. However, the sediments would be expected to lose fluids to the overriding mantle continuously. What relation has the decomposition of chlorite to the formation of calc-alkaline magmas? (Veins we see along chlorite-biotite isograds are not calc-alkaline.) The width of forearc basins, the dip of subducting slabs, the amount of clay subducted, and the composition of the overriding mantle all vary. Even if the positions of two phenomena could be correlated, correlation is not a cause & effect relation.
Unlike increasing temperature or pressure, increasing the amount of water does not increase its thermodynamic escaping tendency. The decomposition of chlorite will not suddenly produce calc-alkaline magmas; it could only increase their amount or change their mode (relative amounts of minerals).
Because of the above reasons for doubt, if there is a popular theory that chorite decomposition produces calc-alkaline magmas, could you make this very clear and give more references, by multiple authors? Thanks very much. (You may wish to keep in mind that theories of plutonism change every decade. This might be a current theory, a working hypothesis. or just the latest idea being explored. Geologist ( talk) 21:49, 23 October 2009 (UTC)