1. Convergent Plate Boundary
* Oceanic-Continental Collision: This is the most common scenario. Here, the denser oceanic basalt plate subducts (dives) beneath the less dense continental granite plate. The process leads to:
* Volcanism: As the basalt plate descends, it melts, generating magma that rises to the surface, forming volcanic arcs on the continental side.
* Mountain Building: The continental plate buckles and folds, creating mountain ranges. The Andes Mountains are a prime example of this type of collision.
* Earthquakes: The subduction zone is a major source of earthquakes, often very powerful.
* Continental-Continental Collision: When two continental plates collide, neither plate can fully subduct because they are both relatively light. This results in:
* Mountain Building: The continents collide and buckle, forming massive mountain ranges like the Himalayas.
* Earthquakes: Powerful earthquakes occur along the collision zone.
2. Transform Plate Boundary
* Lateral Sliding: In this case, the plates slide past each other horizontally. This causes:
* Earthquakes: Friction between the plates releases energy in the form of earthquakes. The San Andreas Fault in California is a prime example of a transform boundary.
3. Divergent Plate Boundary
* Seafloor Spreading: At divergent boundaries, plates move apart. This is where new crust is formed. Granite is not typically found in this setting.
* Volcanism: As the plates separate, magma rises from the mantle to fill the gap, forming new oceanic crust (basalt).
In Summary
* Granite: Granite is typically found in continental crust and is relatively buoyant.
* Basalt: Basalt is found in oceanic crust and is denser than granite.
The behavior of these two rocks when plates collide is driven by the forces of plate tectonics, leading to dramatic geological events like volcanism, mountain building, and earthquakes.
