Geothermal Gradient....as you go deeper and deeper into the earth the pressure increases, which in turn increases the temperature...the geothermal gradient. As a plate is subducted (dives under) another plate, the part that is plunging into the crust will eventually be under enough pressure that it will begin to melt. The molten rock is lower in density then the surrounding material, and will migrate towards the surface.
https://answers.yahoo.com/question/index?qid=20091206183507AAeIJk7
Age of oceanic crust; youngest (red) is along spreading centers. Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics.
https://en.wikipedia.org/wiki/Seafloor_spreading
Water has the effect of lowering the melting temperature of the mantle, thus causing it to melt. The magma produced by this mechanism varies from basalt to andesite in composition. Source(s): http://www.geology.sdsu.edu/how_volcanoe... Bella · 6 years ago.
https://answers.yahoo.com/question/index?qid=20091206183507AAeIJk7
Sometimes a deep ocean trench swallows more oceanic crust than a mid-ocean ridge can produce. Then, if the ridge does not add new crust fast enough, the width of the ocean will shrink. In the Pacific Ocean, subduction through the many trenches that ring the ocean is occurring faster than new crust can be added.
http://www.phschool.com/itext/sci_exp/iText/products/0-13-181243-2/ch1/ch1_s4_4.html
The Process of Subduction. The process by which ocean floor sinks beneath a deep-ocean trench and back into the mantle is called subduction (sub duk shun) . As subduction occurs, crust closer to a mid-ocean ridge moves away from the ridge and toward a deep-ocean trench. Sea-floor spreading and subduction work together.
http://www.phschool.com/itext/sci_exp/iText/products/0-13-181243-2/ch1/ch1_s4_4.html
Water in the subducted rock is released into the asthenosphere. The water lowers the melting temperatures of materials in the asthenosphere, leading to the formation of magma.
http://www.weegy.com/?ConversationId=6FC04846
Best Answer: The crustal portion of the subducting slab contains a significant amount of surface water, as well as water contained in hydrated minerals within the seafloor basalt.
https://answers.yahoo.com/question/index?qid=20091206183507AAeIJk7
Earlier theories (e.g. by Alfred Wegener and Alexander du Toit) of continental drift were that continents ploughed through the sea. The idea that the seafloor itself moves (and carries the continents with it) as it expands from a central axis was proposed by Harry Hess from Princeton University in the 1960s.
https://en.wikipedia.org/wiki/Seafloor_spreading
The destruction of oceanic crust occurs at subduction zones where oceanic crust is forced under either continental crust or oceanic crust. Today, the Atlantic basin is actively spreading at the Mid-Atlantic Ridge. Only a small portion of the oceanic crust produced in the Atlantic is subducted.
https://en.wikipedia.org/wiki/Seafloor_spreading
At the Mid-Atlantic Ridge (and in other areas), material from the upper mantle rises through the faults between oceanic plates to form new crust as the plates move away from each other, a phenomenon first observed as continental drift.
https://en.wikipedia.org/wiki/Seafloor_spreading
what does subduction produce
Subduction produces a crust closer to a mid-ocean ridge moves away from the ridge and toward a deep-ocean trench.  