A fundamental axiom of plate tectonics is that oceanic lithosphere is formed from mantle material at mid-ocean ridge crests and returned to the mantle in subduction zones. Thus, plate creation, movement and destruction provide evidence for convection in the mantle. There must be downwellings in the mantle associated with subduction zones and upwelling beneath mid-ocean ridge crests. However, beyond this, plate tectonics provides no evidence for the location of the return flow in the mantle, or the depth extent of convection other than the seismicity associated with subducting slabs (Section 9.4). One must turn therefore to other lines of evidence for information on the pattern of convection in the deep mantle.
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Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.