Science Olympiad Dynamic Planet Practice Test

What is the relationship between sediment supply and sedimentation in a backarc basin?

1. Sediments come from surrounding continents

2. Active magmatic arcs supply most of the sediment

3. Sedimentation occurs evenly around the basin

4. Ocean currents primarily dictate sediment deposition

The correct answer is: Active magmatic arcs supply most of the sediment

In a backarc basin, active magmatic arcs play a crucial role in the sediment supply due to their geological activity. These arcs, formed from the processes of subduction, produce volcanic material and contribute significantly to sedimentation in nearby basins. As volcanic eruptions and weathering occur, various sediment types are transported from these magmatic arcs into the backarc basin. This relationship means that the volcanic activity not only supplies sediment but also greatly influences the composition and distribution of sediments found within the basin. The proximity of the magmatic arc to the basin makes it a primary source of earthy materials that accumulate as sediment over time, and this supply can be directly correlated with the level of volcanic activity. Additionally, because sediment mainly comes from the magmatic arc, it leads to a specific pattern of sedimentation that is often more concentrated near the arc instead of being evenly distributed throughout the entire basin. This results in sedimentation that is less influenced by external factors like ocean currents, compared to basins where these other influences may play a more dominant role. Understanding this relationship helps in grasping the geological dynamics of backarc basins and their sedimentary processes.