How do tectonic processes primarily influence volcanic activity?

Tectonic processes primarily influence volcanic activity through subduction and rifting processes. When one tectonic plate subducts beneath another, the descending plate melts due to the high temperatures and pressures found in the Earth's mantle. This melting generates magma, which can rise to the surface, resulting in volcanic eruptions. Subduction zones are often associated with explosive volcanic activity due to the release of gases and the interaction of the magma with water.

In rifting zones, tectonic plates move apart, creating fissures that allow magma to escape from the mantle. This can lead to the formation of new volcanic islands and lavas that create new crust as they cool and solidify. Thus, both subduction and rifting are critical processes that directly connect tectonic movements to volcanic activity, explaining why this choice is the correct answer.