Mantle active flow

Largely unseen by human eyes, the ocean basins are alive with volcanic activity. Magma flows upward from the mantle to the ocean bottom not only through rifts, but also through numerous volcanoes and other openings in the ocean floor. Seamounts are submarine voleanoes and ean either be active or extinet. Guyots are extinet voleanoes that were once above sea level, but have sinee subsided below the surface. As they subsided, wave or eur-rent action eroded the top of the volcano to a flat surface. 

Tidal resonances causing spiked heat flow out of liquid outer core into D", causing sharply increased mantle plume activity... 

The first is the reduced heat flow that is heat from the deep interior transmitted mainly by conduction across the crust-mantle boundary. Then there is additional heat associated with tectonic activity within the lithosphere (mountain building and denudation). This component decays rapidly over periods of about 400 million years and so is unimportant except in regions that experienced Phanero-zoic tectonic activity. The third component is heat generated by radioactive decay within the lithosphere this is dominated by upper crustal heat production. This component is estimated at 29 mWnU2. For a 41-km thick crust, this gives an average heat production of about0.7 /rWm 3. 

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