Why must geologists rely on indirect evidence like geologic indicators to understand plate boundaries?

Direct observation is too expensive.

Plate movement is extremely slow.

Most boundaries are underwater.

Earthquakes make it too dangerous.

In the study of plate tectonics, what is the primary purpose of a geologic indicator?

To predict the exact timing of the next volcanic eruption.

To provide evidence for the type and direction of plate movement at a boundary.

To determine the chemical composition of rocks deep within the Earth's mantle.

To directly measure the speed of continental drift in real-time.