ISLAND ARC FORMATION

ISLAND ARC

• Volcanic island arcs are important formations of ocean basin characteristics.
• They are long, curving volcanic island chains located on basin borders.
• Their form is an essential aspect. They are generally concave toward the neighbouring continent and convex toward the ocean basin.
• On the ocean basin side of the arc, a deep trench exists.
• A trench is a long, narrow, and deep topographic low in the ocean bottom that is often found at a converging plate boundary.

Mariana Islands

• Island arcs are generated when one oceanic plate subducts beneath another.
• A plate moves when it goes under another plate. This is called subduction.

Formation of an Island Arc

IMAGE SOURCE

• Plate tectonics is responsible for the genesis of island arcs.
• The bulk of island arcs are found in subduction zones between two plates in the oceanic lithosphere.
• The lithosphere is made up of the hard crust and the topmost mantle.
• The following are the stages of formation:
• Subduction commences as the slab begins to fall into the mantle.
• When the subducting slab reaches around 100 km, it is heated enough for all volatiles, or dissolved components such as water, to be discharged into the overlying mantle.
• Volatiles cause partial melting in the mantle, resulting in magma.
• The magma rises to the surface, underplating the overriding plate's oceanic crust and forming an island arc.

 IMAGE SOURCE (THUMBNAIL)