Question

fill in the blanks for a and b with the choices found below. *
2 points
the model below shows a cross - section of earth at the ocean floor.
the process of a in earths mantle drives the formation of the b shown in the diagram.
convection fusion mid - ocean ridge rift valley subduction trench
a
b

Explanation:

Step1: Analyze Process A

In Earth's mantle, the process that drives tectonic activity (like ocean - floor features) is convection. Convection currents in the mantle occur due to the heat from the Earth's core, causing the mantle material to move in circular patterns (as seen in the diagram's circular arrows). Fusion is a nuclear process (not related to mantle movement), and subduction is a process at plate boundaries (not the driving process in the mantle here). So for A, the correct choice is convection.

Step2: Analyze Feature B

The diagram shows a feature at the ocean floor with a central opening (like a mid - ocean ridge). A mid - ocean ridge is formed by mantle convection driving the separation of tectonic plates, allowing magma to rise. A rift valley is usually on land, a trench is a subduction - related feature (not what's shown here). So for B, the correct choice is mid - ocean ridge.

Answer:

A. convection
B. mid - ocean ridge