As plate A continues to move downward into the mantle, particularly in a subduction zone scenario where it is an oceanic plate converging with a continental or another oceanic plate, several key processes occur at its leading edge:
- The leading edge of plate A will be subjected to increasing temperature and pressure as it descends into the mantle. This causes the leading edge to melt, transforming it into magma
- The magma generated from the melting leading edge can rise toward the surface, leading to volcanic activity such as the formation of volcanoes or volcanic island arcs above the subduction zone
- The subduction of plate A also produces geological features like deep ocean trenches at the point where it bends downward, and can cause deformation of the plate's leading edge due to bending and breaking under pressure
- The interaction between plate A and the overriding plate generates seismic activity, including earthquakes, as stresses accumulate along the convergent boundary
- Additionally, if the leading edge suddenly moves upward, it can displace large volumes of ocean water, potentially triggering tsunamis
In summary, the leading edge of plate A will melt into magma due to high mantle temperatures, contribute to volcanic activity, deform under pressure, and be involved in seismic and tsunami-generating processes as it subducts beneath another plate
