I know this is a bit of an odd question, its for my geology essay and I really don't have a clue. Is it anything to do with density? or fractination in a magma chamber? I am confused!
2006-12-16 05:45:51 · 7 answers · asked by seashellamanda 1 in Science & Mathematics ➔ Earth Sciences & Geology
I'm not at home at the moment so cannot check my references, but I believe that the rhyolitic magma contains a higher proportion of quartz and perhaps water. Therefore they are more likely to be associated with magmas passing though or interacting with continental crust. Check, but this may point to rhyolites being formed at destructive plate boundaries.
Basaltic magmas are the main constituent of oceanic crust, forming plates at the mid-ocean spreading zones. Therefore since they form the basis of the ocean floors, basalt would be volumetrically more important.
2006-12-16 06:03:50 · answer #1 · answered by 13caesars 4 · 0⤊ 0⤋
Rhyolites, and acid igneous rocks in general, are derived magmas, that is they form by fractional crystalisation. Basalt is a more "fundamental" magma. As a basic magma rises it will start to crystalise, high-temperature minerals first. This means the lower temperature minerals like quartz and K-feldspar, as well as the volatiles like water, get concentrated. Furthermore, even when acid magmas develop, they often fail to arrive at the surface to form lavas, which is what rhyolite normally specifically is, because once the volatiles are lost on eruption, the melting point is raised, so the magma "freezes". This tendency to emit volatiles then bung up the ent is what makes acid volcanoes like Mt St. Helens or Vesuvius so dangerous.
2006-12-18 17:31:12 · answer #2 · answered by Paul FB 3 · 0⤊ 0⤋
Rhyolites contain the less-dense minerals, thus are extruded to the surface more easily than heavier basalts containing more iron and dense minerals. Volcanoes release lighter mineral compositions, ie., lighter minerals float higher up in the magma than heavier which sink. Over geologic time for the life of a volcano, you can follow rhyolites, andesites, and higher quartz content minerals in the first eruption phases, then over geologic time thousands of years as the volcano dies out, the heavier mafic metals are extruded.
2006-12-16 21:17:49 · answer #3 · answered by alaskasourdoughman 3 · 0⤊ 0⤋
Well I was talking to my mate from Cambridge who has an essay due tomorrow, and came to the conclusion that rhyolitic magma has less minerals per cm cubed than basaltic magma...
2006-12-18 21:37:57 · answer #4 · answered by Anonymous · 0⤊ 0⤋
What do you mean by "less important"? All of the minerals on earth are here for a reason. Just because rhyolite is less dense does not mean it is less important. Basalts are more prevalent because there is more oceanic crust, but it is not more important.
2006-12-16 19:40:20 · answer #5 · answered by Anonymous · 0⤊ 0⤋
The oceanic crust is the result of differentiation of the mantle/crust boundary, and the mantle is a major portion of the Earth. The continental crust is a result of differentiation of "lighter" continental minerals with "heavier" oceanic minerals. The mantle is constantly renewing oceanic crust all around the Earth whereas continental crust is being generated in certain oceanic/continental margins (or oceanic/oceanic margins), which is a lot fewer places.
2006-12-16 19:00:19 · answer #6 · answered by Amphibolite 7 · 0⤊ 0⤋
I think you use one in cakes and the other one in biscuits - dont trust me though, l dont know much ;-)
2006-12-16 13:51:11 · answer #7 · answered by max 4 · 0⤊ 0⤋