Changes

Divergent plate boundary displays the phenomenon of sea-floor spreading. Mid-Oceanic Ridge (MOR) is the place where magma from below the Earth emerges and crystallizes as oceanic crust. The spreading of the sea-floor causes decompression, triggering partial melting of the source rock. Generation of oceanic crust in MOR enables it to be the youngest crust making up the Earth. No oceanic crust is found to be older than Jurassic.

Divergent plate boundary displays the phenomenon of sea-floor spreading. Mid-Oceanic Ridge (MOR) is the place where magma from below the Earth emerges and crystallizes as oceanic crust. The spreading of the sea-floor causes decompression, triggering partial melting of the source rock. Generation of oceanic crust in MOR enables it to be the youngest crust making up the Earth. No oceanic crust is found to be older than Jurassic.

Due to interaction with seawater, magma crystallizes as pillow lava with basalt composition. Oceanic crust is not homogenous structurally. Keary and Vine<ref name=KV>Keary, Philip and Vine, Frederick J. 1994. Geoscience Texts: Global Tectonics. Oxford: Blackwell Scientific Publications.</ref> divides oceanic crust into three layers. Layer 1, the uppermost part, consists of sedimentary cover varying from pelagic sediments, limestone, clays, and chert. Consolidated sediment and extrusive igneous materials form the Layer 2. Layer 3 gives plutonic foundation with gabbroic composition and consists of serpentinized materials.

Due to interaction with seawater, magma crystallizes as pillow lava with basalt composition. Oceanic crust is not homogenous structurally. Keary and Vine<ref name=KV>Keary, P. and F. J. Vine, 1994, Geoscience Texts: Global Tectonics. Oxford: Blackwell Scientific Publications.</ref> divides oceanic crust into three layers. Layer 1, the uppermost part, consists of sedimentary cover varying from pelagic sediments, limestone, clays, and chert. Consolidated sediment and extrusive igneous materials form the Layer 2. Layer 3 gives plutonic foundation with gabbroic composition and consists of serpentinized materials.

Continental crust is found ranging in age from Hadean to recent. The thickness of this crust ranges from 35 – 40 km and 38 km on average. Continental crust is composed of two layers: upper and lower continental crust. Kearey and Vine<ref name=KV /> stated that upper continental crust is composed of granodiorite and diorite composition. Lower continental crust requires seismic observations since the rock is not exposed on the surface. Seismic velocity, ranging from 6,5 – 7,6 km s-1, represents that rocks are more felsic than basalt constructing the lower continental crust. Roberts and Bally (2012) states that granulite or pyroxene granulite forms lower continental crust.

Continental crust is found ranging in age from Hadean to recent. The thickness of this crust ranges from 35 – 40 km and 38 km on average. Continental crust is composed of two layers: upper and lower continental crust. Kearey and Vine<ref name=KV /> stated that upper continental crust is composed of granodiorite and diorite composition. Lower continental crust requires seismic observations since the rock is not exposed on the surface. Seismic velocity, ranging from 6,5 – 7,6 km s-1, represents that rocks are more felsic than basalt constructing the lower continental crust. Roberts and Bally (2012) states that granulite or pyroxene granulite forms lower continental crust.