Continental crust is composed of two layers: upper and lower continental crust. The thickness of this crust ranges from 35–40 km and 38 km on average. Layer 3 gives plutonic foundation with gabbroic composition and consists of serpentinized materials.Ĭontinental crust is found ranging in age from Hadean to recent. Consolidated sediment and extrusive igneous materials form the Layer 2. Layer 1, the uppermost part, consists of sedimentary cover varying from pelagic sediments, limestone, clays, and chert. Keary and Vine divides oceanic crust into three layers. Oceanic crust is not homogenous structurally. No oceanic crust is found to be older than Jurassic.ĭue to interaction with seawater, magma crystallizes as pillow lava with basalt composition. Generation of oceanic crust in MOR enables it to be the youngest crust making up the Earth. The spreading of the sea-floor causes decompression, triggering partial melting of the source rock. Mid-Oceanic Ridge (MOR) is the place where magma from below the Earth emerges and crystallizes as oceanic crust. Continental crust, chemically, tends to have more felsic mineralogical composition than oceanic one.ĭivergent plate boundary displays the phenomenon of sea-floor spreading. Continental and oceanic crust makes up nearly three-fourths of the Earth’s body, providing sources of sediment and basement of basins. The Earth’s crust triggers the questions of Earth scientists regarding its formation and evolution through time. 4.2.1 Provenance of Sedimentary Rock in Subduction Zone.
SUBDUCTION ZONE SERIES
![subduction zone subduction zone](https://www.kids-fun-science.com/images/rf14-subduction-zone-usgs.jpg)
4.1.1 Thermal Structure of Subduction Zone.3 Structural Features of Subduction Zone.