6. Why are most of the world’s volcanoes located at divergent plate boundaries,
ID: 159111 • Letter: 6
Question
6. Why are most of the world’s volcanoes located at divergent plate boundaries, close to convergent plate boundaries, or at hot spots? Why is it very rare to encounter volcanoes at other locations?
A. The current pressure and temperature conditions in the mantle are not conductive to generating magma for volcanism.
B. Wet rock melting and decompression melting explain magma generation.
C. Magma generation is not random and must be generated through functions of volatiles and decompression.
D. Divergent, Convergent, and hotspots tectonic processes after nonmelting conditions in the mantle through P and T changes that provide melting sources for volcanism at these location.
7. During the differentiation, as the magma crystallizes into minerals; what can be said about the composition of those crystals?
A. More felsic
B. They are the same composition as the magma itself.
C. More mafic.
D. Intermediate in composition
8. Two minerals that crystalize from common magmas are Olivine and Quartz. If a magma liquid is getting enriched in Si and depleted in Mg as it cools and starts to crystalize, which of these minerals crystalizes first? Why?
A. Olivine because it is more dense and sinking to the bottom to be remelted. This process will lead to factional melting and an enriched silica conduit.
B. Quartz because it is the most common constituent of all igneous material and is therefor the most common mineral to form.
C. Quartz, this is the most common mineral on Earth and therefor is what is crystalizing out in the magma.
Olivine because the silica content is enriching and the Mg content is decreasing because it is crystallizing out.
Explanation / Answer
6.Pressure and temperature increase , causes changes to the plate that melt the mantle above.
D. Divergent, Convergent, and hotspots tectonic processes after nonmelting conditions in the mantle through P and T changes that provide melting sources for volcanism at these location.
7
A. More felsic
The most common felsic rocks are granite and rhyolite, which represent the end product of the Earth's crustal differentiation process
8. This sequential order of crystallizing silicate minerals is from olivine to quartz.
Olivine because the silica content is enriching and the Mg content is decreasing because it is crystallizing out.
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