A lava flow down the side of a volcano destroys all vegetation and eventually turns into volcanic rock when it cools and hardens:

A lava flow destroys the existing vegetation and leaves newly formed rock with little or no soil. The gradual establishment of life in an area without soil is primary succession, so the correct choice is primary succession. Secondary succession occurs when a disturbance leaves the soil intact, such as after a fire.

AI-written and checked against the verified answer.