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Subduction zone is one of the most critical tectonic phenomena on Earth. Its correlation to the formation of volcanic arc, deep earthquake, and basins attract the minds of geologists. Profound role of subduction zone emerges as methods in geophysics reveal the structure and composition of materials deep beneath the Earth’s surface.

Subduction zone is one of the most critical tectonic phenomena on Earth. Its correlation to the formation of volcanic arc, deep earthquake, and basins attract the minds of geologists. Profound role of subduction zone emerges as methods in geophysics reveal the structure and composition of materials deep beneath the Earth’s surface.

Principally, subduction zone is the area of the Earth where two plates colliding and the one sinking inside the Earth. The primary cause of subducting slab beside compression is density. Crust with higher density tends to move inside the Earth. According to the types of involved crust, subduction zone has two separate types: island-arc and active [[continental margin]] (ACM). Island-arc only involves oceanic crust, while ACM encompasses both continental and oceanic crust.

Principally, subduction zone is the area of the Earth where two plates colliding and the one sinking inside the Earth. The primary cause of subducting slab beside compression is density. [[Crust]] with higher density tends to move inside the Earth. According to the types of involved crust, subduction zone has two separate types: island-arc and active [[continental margin]] (ACM). Island-arc only involves oceanic crust, while ACM encompasses both continental and oceanic crust.

==The Earth’s Crust==

==The Earth’s Crust==

==Principles of Subduction Zone==  

==Principles of Subduction Zone==  

===Forces in Subduction Zone===

===Forces in Subduction Zone===

Oceanic crust generated in MOR will migrate nearer to the trench. Driving mechanism which influences the dynamics of subduction zone is density. Oceanic crust is denser than continental one, therefore the sinking of oceanic crust below continental crust is possible. Forces driving subduction are ridge-push and slab-pull. As oceanic crust moves away from the ridge, conductive cooling turns the crust to be denser. Density of oceanic crust varies laterally, increasing from the ridge axis to the trench. Such force is parallel to the plate since it pushes in topographic slope. Slab-pull force involves cold, dense oceanic lithosphere and hot, lighter [[mantle]]. Slab-pull force dominantly accommodates the vertical displacement of plate. This provides the biggest force for oceanic crust to sink.

Oceanic [[crust]] generated in MOR will migrate nearer to the trench. Driving mechanism which influences the dynamics of subduction zone is density. Oceanic crust is denser than continental one, therefore the sinking of oceanic crust below continental crust is possible. Forces driving subduction are ridge-push and slab-pull. As oceanic crust moves away from the ridge, conductive cooling turns the crust to be denser. Density of oceanic crust varies laterally, increasing from the ridge axis to the trench. Such force is parallel to the plate since it pushes in topographic slope. Slab-pull force involves cold, dense oceanic lithosphere and hot, lighter [[mantle]]. Slab-pull force dominantly accommodates the vertical displacement of plate. This provides the biggest force for oceanic crust to sink.

Resistive forces are also present in convergent plate boundary. As oceanic crust moves laterally, the base of the plate produces shear resistance, causing deformation of mantle wedge. The contact between oceanic and continental crust along fault plane creates frictional force. On the other hand, when subducted slab enters the depth of 670 km, resistance to penetration occurs because facing discontinuity.

Resistive forces are also present in convergent plate boundary. As oceanic crust moves laterally, the base of the plate produces shear resistance, causing deformation of mantle wedge. The contact between oceanic and continental crust along fault plane creates frictional force. On the other hand, when subducted slab enters the depth of 670 km, resistance to penetration occurs because facing discontinuity.

==Structural Features of Subduction Zone==  

==Structural Features of Subduction Zone==  

===Ocean Trenches===

===Ocean Trenches===

Underthrusting of oceanic crust beneath continental crust creates the deepest morphology on Earth: ocean trench. Ocean trench on average has width of 50 – 100 km. As an example, Peru-Chile trench is 4500 km long and has depth of 7 – 8 km below sea level. Great depth of ocean trench implies to its gravity anomalies, reaching negative 2000 gu. On [[cross-section]], trench has V-shaped morphology with angle of steepest slope ranging from 8 – 20o on the opposite side of underthrusting oceanic crust. Sediment supply of oceanic trench depends on accumulated materials (terrigenous, pelagic, or carbonate sediments) on ocean floor.

Underthrusting of oceanic [[crust]] beneath continental crust creates the deepest morphology on Earth: ocean trench. Ocean trench on average has width of 50 – 100 km. As an example, Peru-Chile trench is 4500 km long and has depth of 7 – 8 km below sea level. Great depth of ocean trench implies to its gravity anomalies, reaching negative 2000 gu. On [[cross-section]], trench has V-shaped morphology with angle of steepest slope ranging from 8 – 20o on the opposite side of underthrusting oceanic crust. Sediment supply of oceanic trench depends on accumulated materials (terrigenous, pelagic, or carbonate sediments) on ocean floor.

===Accretionary Prism===

===Accretionary Prism===