Structure of the Earth
Prior to the proposal of the plate tectonic theory, scientists had divided the earth’s interior into three layers: -
1. Core
· composed of dense rocks containing iron and nickel alloys
· divided into a solid inner core and a molten outer core with a temperature of over 5000 degrees Celsius
2. Mantle
· split into upper and lower mantles composed of molten and semi-molten rocks
3. Crust
· varies in thickness
· 2 types-continental and oceanic
1. Core
· composed of dense rocks containing iron and nickel alloys
· divided into a solid inner core and a molten outer core with a temperature of over 5000 degrees Celsius
2. Mantle
· split into upper and lower mantles composed of molten and semi-molten rocks
3. Crust
· varies in thickness
· 2 types-continental and oceanic
The LISTHOSPHERE (the earth’s crust and the rigid upper part of the mantle) is divided into plates. The rigid plates float on the ASTHENOSPHERE (semi-molten mantle) and are moved by CONVECTION CURRENTS.
TYPEs of crust
Continental Crust or SIAL is composed of older, lighter rock of granite type. It is dominated by minerals rich in Silica (Si) and aluminum (Al) from which the term is derived.
Oceanic Crust or SIMA consists of much younger, denser rock of basaltic composition. Its dominant minerals are silica (Si) and magnesium (Ma).
Comparison of the 2 types of crust:
Oceanic Crust or SIMA consists of much younger, denser rock of basaltic composition. Its dominant minerals are silica (Si) and magnesium (Ma).
Comparison of the 2 types of crust: