How does geothermal gradient vary at subduction zones?

Geothermal Gradient can be simply defined as the rate at which the temperature increases in the Earth's interior with depth. Thid gradient varies from place to place but it averages out between 25 to 30 degrees per kilometer. read more

Low geothermal gradient in the subduction zone: Temperature increases slowly with depth at subduction zones. This is due to the relatively cool sediments and fluids (i.e.: seawater) being subducted along with old, cold ocean lithosphere that penetrates to great depths. read more

Decreasing the subduction angle from 27° to 3.6° increases gradients by about a factor of 2 at both deep and shallow levels. Decreasing the subduction rate by a factor of 8 (160 to 20 km/m.y.) increases gradients by about a factor of 2 when frictional heating at the plate contact is excluded, and less when modest amounts of frictional heating are included. read more