Science Olympiad Dynamic Planet Practice Test

Which force is considered the strongest among the three main forces acting on tectonic plates?

1. Ridge push

2. Slab pull

3. Slab/trench suction

4. Gravitational pull

The correct answer is: Slab pull

Slab pull is recognized as the strongest force among the main driving mechanisms of tectonic plate movement. This force arises when an oceanic plate subducts, or sinks, into the mantle at convergent plate boundaries. As the denser oceanic plate encounters the less dense continental plate, it begins to descend due to gravity. The process is facilitated by the weight of the subducting plate itself, which exerts a pulling force on the surrounding tectonic plates. This descending motion creates significant stress and can lead to tectonic activity such as earthquakes and volcanic eruptions. Notably, slab pull is more effective in driving plate motions compared to the other forces, such as ridge push, where new crust is formed at mid-ocean ridges, and gravitational pull, which is more generalized and does not directly drive plate movement like slab pull does. Understanding the dynamics of plate tectonics highlights the importance of slab pull in shaping the Earth's surface over geological timescales, cementing its role as a dominant force in tectonic activity.