The above cartoon is a cross sectional view showing a magmatic (island) arc, a s
ID: 803750 • Letter: T
Question
The above cartoon is a cross sectional view showing a magmatic (island) arc, a subduction zone, a spreading ridge, and a continent. Numbers 1 to 4 mark the location of a certain type of partial melting mechanism. Some of these numbers may repeat the same mechanism. Answer the questions 1 through 4 below corresponding to the number on the figure above and note well the additional guidance in terms of where the melting takes place (i.e what sort of rock is partially melted and where). Partial melting of asthenosphere occurs at this location (name the process AND describe it) (see previous page for diagram and instructions).Explanation / Answer
Hot Spot:
A hot Spot is a localised source of basaltic magma that is stationary in the asthenosphere. The basaltic magma produced by partial melting of mantle in a concentrated zone of the asthenosphere. They may be on, near to, or far from tectonic plate boundaries. Two hypotheses attempt to explain their origin. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. If a continental plate moves over the hotspot, basaltic and felsic volcanism occur. The felsic magmas form as the rising basaltic magma melts some of the continental crust. Because the region is usually under tension, these felsic magmas can rise and erupt forming rhyolite. Basaltic magmas erupt as well.
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