Science Olympiad Dynamic Planet Practice Test

What characterizes a backarc basin at a convergent plate boundary?

1. Asymmetric seafloor spreading

2. Formation of rift valleys

3. High volcanic activity

4. Subduction of oceanic crust

The correct answer is: Asymmetric seafloor spreading

A backarc basin is characterized primarily by asymmetric seafloor spreading due to the tectonic processes occurring at convergent plate boundaries. When an oceanic plate subducts beneath another tectonic plate, it often leads to the formation of a volcanic arc on the overriding plate. In the backarc region, the movement and dynamic extension can lead to the development of a basin that exhibits asymmetric seafloor spreading, where one side of the basin spreads faster than the other. This asymmetry results from various geological forces at play during the convergence and the associated movements of the plates. While high volcanic activity and the subduction of oceanic crust are indeed features related to convergent boundaries, they are generally associated with the volcanic arc itself rather than the backarc basin itself. Additionally, rift valleys typically form at divergent boundaries, where tectonic plates move away from each other rather than converging. The unique characteristics of a backarc basin, especially the asymmetric nature of the seafloor spreading, highlight the complex interactions at these convergent boundaries.