Science Olympiad Dynamic Planet Practice Test

What does slab pull primarily result from?

1. The weight of a dense oceanic plate

2. The rising of magma

3. The collision of lithospheric plates

4. The thinning of the crust

The correct answer is: The weight of a dense oceanic plate

Slab pull is a geological process primarily driven by the weight and density of an oceanic plate as it sinks into the mantle at subduction zones. As an oceanic plate, which is generally denser than the underlying asthenosphere, moves away from mid-ocean ridges and begins to subduct beneath lighter continental crust, its own weight causes it to pull the rest of the tectonic plate along with it. This action is one of the crucial mechanisms that contributes to the movement of tectonic plates. The other processes provided in the choices do not primarily contribute to slab pull. Magma rising is associated with processes like mantle convection and volcanic activity, rather than with the descending slab itself. The collision of lithospheric plates can result in various tectonic activities, such as mountain building or earthquakes, but it is not the mechanism behind slab pull. Crust thinning generally pertains to rifting or continental break-up rather than to the specific interaction between a subducting plate and the mantle. Therefore, the correct answer focuses on the role of the oceanic plate's weight, which is central to the concept of slab pull in plate tectonics.