Convergent plate boundaries

• At convergent plate boundaries plates collide.
• When two plates collide the heavier plate is pulled downwards along the Benioff Zone beneath the other.
• This process is called subduction.
• The subduction zone is the point at which subduction occurs.
• There are 3 types of Convergence: Oceanic Plate to Oceanic Plate, Oceanic Plate to Continental Plate, Continental Plate to Continental Plate.
• When two oceanic plates collide, the heavier plate is subducted under the other, forming long deep narrow oceanic trenches.
• As the heavier plate is pulled downwards it heats up and melts forming magma.
• The magma rises to the ocean surface in the form of a volcanic eruption, forming offshore islands or island arches such as Japan.
• The Mariana Trench has formed where the Pacific Plate collides with the Philippines Plate, and is 11kms deep, so deep that Mount Everest (8kms+) would fit comfortably into the Mariana Trench.
• When an oceanic plate collides with a continental plate, the heavier oceanic plate subducts beneath the lighter continental plate in a process called 'Subduction'.
• The continental plate is buckled and deformed.
• The subduction zone is usually marked by a 'deep ocean trench'.
• The subducting oceanic plate begins to melt and disintegrate along the 'benioff zone' and eventually merges with the underlying magma.
• The collision forms volcanic mountains.
• The Andes were formed when the Nazca Plate was subducted under the South American Plate.
• The collision of an oceanic plate and continental plate may also result in faulting - rocks are shunted forward and horizontally.
• The Gweebarra Fault in Donegal was formed in this way.
• When two continental plates collide, Fold Mountains are formed.
• When the Indian Plate collided with the Eurasian Plate, the Himalayas were formed.
• The Himalayas lay under the sea but were forced upwards due to the collision, containing the fossilised remains of dead marine organisms.
• The Fold Mountains of North West Ireland, Scotland and Scandinavia were formed when two continental plates collided.