1. The texture of the ocean floor shown at A is smooth and relatively flat, indicating it is composed of fine-grained sediments that have accumulated over time.
2. At B, the process occurring is seafloor spreading. Magma from the mantle rises through a rift in the oceanic crust, cools, and solidifies to form new oceanic crust. This results in the formation of new seafloor and the gradual widening of the ocean basin.
3. Old oceanic crust is destroyed when it is subducted beneath another tectonic plate at a convergent boundary. As the denser oceanic plate sinks into the mantle, it melts due to high temperatures and pressures, recycling the crustal material back into the mantle.
4. Three kinds of evidence scientists have found to support seafloor spreading are:
- Magnetic striping on the ocean floor, which records reversals of Earth’s magnetic field as new crust forms.
- The age of the oceanic crust, which increases with distance from mid-ocean ridges.
- The thickness of sediment layers, which is thinnest near the ridge and thickens farther away, indicating older crust has had more time to accumulate sediment.
5. At C, compressional pressure is occurring as two tectonic plates converge. This causes the oceanic plate to be forced downward into the mantle in a process called subduction, often forming deep ocean trenches and volcanic arcs.
6. Device: sonar
7. Feature: mid-ocean ridge
8. Process: seafloor spreading
9. Principle: convection currents
10. Chain: mid-ocean ridge
Parent Tip: Review the logic above to help your child master the concept of ocean floor features worksheet.
