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Ali Hamza
Ali Hamza
Mechanical
22 Jan 2019

Crust and its Types :

The Crust:

Outer layer

2 types of crust

1. Oceanic (very dense, made of basalt)

2. Continental (less dense, made of granite)

Continental Crust

0.374% of Earth's mass;

 depth of 0-50 kilometers (0 - 31 miles).

The continental crust contains 0.554% of the mantle-crust mass.

This is the outer part of the Earth composed essentially of crystalline rocks. 

 These are low-density buoyant minerals dominated mostly by quartz (SiO2) and feldspars (metal-poor silicates). 

The crust (both oceanic and continental) is the surface of the Earth; as such, it is the coldest part of our planet.  Because cold rocks deform slowly, we refer to this rigid outer shell as the lithosphere (the rocky or strong layer).

Oceanic Crust

0.099% of Earth's mass;

depth of 0-10 kilometers (0 - 6 miles)

The oceanic crust contains 0.147% of the mantle-crust mass.

The majority of the Earth's crust was made through volcanic activity.  

 The oceanic ridge system, a 40,000-kilometer (25,000 mile) network of volcanoes, generates new oceanic crust at the rate of  17 km3 per year, covering the ocean floor with basalt. Hawaii and  Iceland are two examples of the accumulation of basalt piles.  

Seismic waves move faster through the oceanic crust that through the continental crust. 

 It is also called as “Sima” while Continental Crust as “Sial”.