1. Based on the theory of plate tectonics, you would expect to find very little rock or very old rock in an oceanic ridge. This is because oceanic ridges are divergent boundaries where new oceanic crust is continuously formed as magma rises and solidifies. The rock at the ridge itself is therefore the youngest, and as you move away from the ridge, the rock gets progressively older.
2. Based on the theory of plate tectonics, you would expect to find very new rock in an oceanic trench. This is because oceanic trenches are convergent boundaries where one tectonic plate is being subducted beneath another. As the plates converge, the overriding plate may be pushed upward to form mountains or volcanic arcs, while the subducting plate carries older oceanic crust down into the mantle. However, the process of subduction can also lead to the formation of new igneous rock through melting and volcanism near the trench, particularly in the overriding plate. Additionally, sediments scraped off the subducting plate can accumulate and form new rock layers in the trench area.
3. Based on the information, the Mariana Plate is likely a small, independent tectonic plate situated between the Pacific Plate and the Philippine Sea Plate. It is being subducted under the Philippine Sea Plate along the Mariana Trench, which is why it is described as “the deepest oceanic trench in the world.” The fact that there is a boundary between two tectonic plates (Pacific and Mariana) suggests that the Mariana Plate is distinct from the Pacific Plate and is moving independently, even if it is relatively small compared to major plates.
Parent Tip: Review the logic above to help your child master the concept of plate tectonics worksheet answers.
