Oceanic-oceanic convergence describes the process where two oceanic plates collide, and one is forced beneath the other. Here's how it works:
The Subduction Process
At an oceanic-oceanic convergent boundary, one of the oceanic plates is subducted under the other. This means it is pushed down into the Earth's mantle.
- Plate Density: The plate that subducts is usually the older and colder one because it is denser than the younger, warmer plate, as referenced in the provided information.
- Subduction Zone: The area where this subduction occurs is called a subduction zone.
Key Characteristics of Oceanic-Oceanic Convergence
| Feature | Description |
|---|---|
| Plate Interaction | One oceanic plate is forced under another. |
| Driving Force | Density differences, typically older, colder plates subduct. |
| Resulting Landforms | Volcanic island arcs, deep-sea trenches, earthquakes, and tsunamis can be caused by subduction. |
| Reference | Figure 4.6.1 explains how the plates are pushed under one another, focusing on density. |
Effects of Subduction
- Melting and Magma Generation: As the subducting plate descends into the mantle, the increased temperature and pressure cause the rock to melt. This molten rock, called magma, rises to the surface.
- Volcanic Island Arcs: The magma that reaches the surface often forms a chain of volcanic islands. These are known as island arcs. Examples include the Marianas Islands and the Aleutian Islands.
- Earthquakes: The movement of the plates, particularly the subduction process, often results in earthquakes.
- Deep-Sea Trenches: Where one plate is subducted, a deep trench forms in the ocean floor.
In summary
Oceanic-oceanic convergence occurs when two oceanic plates collide, with the denser, older plate subducting beneath the other. This process leads to the formation of island arcs, earthquakes, and deep-sea trenches, and is primarily driven by the density differences between the colliding plates.
