Science Olympiad Dynamic Planet Practice Test

During which phase of the Wilson cycle does continental rifting occur?

1. Initial expansion

2. Mid-ocean ridge formation

3. Subduction onset

4. Continental collision

The correct answer is: Initial expansion

Continental rifting occurs during the initial expansion phase of the Wilson cycle. In this phase, tectonic forces create tension in the continental lithosphere, leading to the stretching and thinning of the crust. This process can result in the formation of rift valleys, where the land sinks and fractures due to the extensional forces acting on it. As rifting continues, a body of water may eventually form in the rift, leading to the creation of a new ocean basin. During the subsequent phases of the Wilson cycle, such as mid-ocean ridge formation, subduction onset, and continental collision, the geological processes differ significantly. Mid-ocean ridge formation is associated with the divergent boundaries where new oceanic crust is created, while subduction onset involves one tectonic plate being forced under another, leading to various geological phenomena such as volcanic arcs. Continental collision, on the other hand, occurs when two continental plates converge, causing mountain building and other complex interactions. Understanding where continental rifting fits into this cycle is crucial for grasping the dynamics of plate tectonics and the geological evolution of the Earth.