When plate A collides with plate B, the outcome depends on their types and densities. Typically, if plate A is an oceanic plate and plate B is a continental plate, plate A, being denser and thinner, subducts beneath plate B. This subduction causes plate A to sink into the mantle beneath plate B, forming a deep ocean trench at the collision zone
. As plate A descends, the increasing heat and pressure cause parts of it to melt, generating magma. This magma rises through plate B's crust, potentially leading to volcanic activity and the formation of volcanic arcs on plate B
. The collision also generates earthquakes due to the intense stress and friction between the plates
. If both plates are continental, their collision results in the buckling and thickening of the crust rather than subduction because continental crust is less dense and more buoyant. This process forms mountain ranges, such as the Himalayas, where the two continental plates have been pushed upward over millions of years
. In summary:
- Plate A (denser oceanic plate) subducts beneath plate B (continental plate), forming trenches, volcanic arcs, and earthquakes.
- If both plates are continental, they collide and crumple, creating mountain ranges without significant subduction
This occurs because denser oceanic crust sinks beneath lighter continental crust, while buoyant continental crust resists subduction and instead uplifts
