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(1) At age < 50 Myr, the data is somewhat below
the theory and scattered. This is due to
hydrothermal circulation of sea water that occurs
in the fracture and cracks in oceanic crust. Hightemperature (~500 ℃) vents (black smokers)
have been observed in the vicinity of the ridges.
(2) At age > 80 Myr, the observed surface heat
flux is above the theory. The difference can be
attributed to additional heat transfer to the base
of the lithosphere.
Heat sources include the secondary convection
beneath the lithosphere associated with mantle
plumes or subduction and viscous dissipation in
the asthenospheric shear flow.
The End