* Divergent plate boundaries: These are areas where plates move apart. This creates space for magma to rise from the mantle, leading to volcanic activity and the formation of new crust. The heat from this rising magma significantly increases the geothermal gradient.

* Subduction zones: These are areas where one plate dives beneath another. The descending plate, composed of older, colder oceanic crust, gets heated by friction and the surrounding mantle. This process creates a significant heat flow, resulting in a higher geothermal gradient in the area directly above the subduction zone.

So, which has a greater geothermal gradient?

* Near the surface, subduction zones typically have a steeper geothermal gradient. This is due to the heat generated by the descending plate.

* Deeper in the Earth, divergent plate boundaries have a greater geothermal gradient. The rising magma from the mantle keeps the region hot, and the newly formed crust is relatively thin, allowing for heat to escape more readily.

In summary:

* Near the surface: Subduction zones have a steeper geothermal gradient.

* Deeper in the Earth: Divergent plate boundaries have a greater geothermal gradient.

It's important to consider the depth when comparing geothermal gradients between these two types of plate boundaries.