With the aid of diagrams describe and explain the formation of landforms found near convergent plate boundaries. [10]

One landform found near convergent boundaries are coastal fold mountains. This is through the process of subduction over billions of years. This transforms island arcs (as shown in the diagram) into continental landmasses. This is because sediments (as will be shown in the diagram) are added to the leading edge of the non-subducted plate, instead of a normal subduction. Thus, as this plate is subject to compression and covergence (S. American plate in this instance) at its leading edge, it is uplifted and folded to create fold mountains which is the Andes here. The Nazca Plate is subducted since it is a oceanic plate and therefore more dense, and an ocean trench is formed between the plates. Further down is the subduction zone and this collision will often cause earthquakes, and there are plutons in the South American plate, which are very hot bits of igneous rock due to its proximity to the volcano.The second landform is a volcanic island arc. The two plates are travelling towards each other at around 50mm a year and when they collide it causes them to converge. This is between two oceanic plates, with the denser subducting. It is forced to a depth of around 700km, and as it subducts higher sediments are scraped off it onto the leading edge of the non-subducted plate, forming an accretionary wedge which forms the foundations of the island arc. Some of these sediments are partially subducted but the dissolved water lowers their melting point so they form a molten mass called a batholith. These penetrate up through the ground and cause plutons and explosive cone volcanoes as shown in the diagram.