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Geography

Composition of earth

Composition of whole earth:

Earth's mass

Approximately 5.97×1024 kg.

Composition of whole earth

Iron - 32.1%

Oxygen - 30.1%

Silicon - 15.1%

Magnesium - 13.9%

Sulfur - 2.9%

Nickel - 1.8%

Calcium - 1.5%

Aluminum - 1.4% and the remaining 1.2% consisting of trace amounts of other elements.

Due to mass segregation, the core region is believed to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.

 

Composition of the crust:

Compound

Formula

Continental

composition

Oceanic

composition

Silica

SiO2

60.2%

48.6%

Alumina

Al2O3

15.2%

16.5%

Lime

CaO

5.5%

12.3%

Magnesia

MgO

3.1%

6.8%

Iron(II) oxide

FeO

3.8%

6.2%

Sodium oxide

Na2O

3.0%

2.6%

Potassium oxide

K2O

2.8%

0.4%

Iron(III) oxide

Fe2O3

2.5%

2.3%

Water

H2O

1.4%

1.1%

Carbon dioxide

CO2

1.2%

1.4%

Titanium dioxide

TiO2

0.7%

1.4%

Phosphorus pentoxide

P2O5

0.2%

0.3%

 

Total

99.6%

99.9%

 

The geochemist F. W. Clarke calculated that a little more than 47% of Earth's crust consists of oxygen. The more common rock constituents of the crust are nearly all oxides; chlorine, sulfur and fluorine are the important exceptions to this and their total amount in any rock is usually much less than 1%. The principal oxides are silica, alumina, iron oxides, lime, magnesia, potash and soda. The silica functions principally as an acid, forming silicates, and all the most common minerals of igneous rocks are of this nature. From a computation based on 1,672 analyses of all kinds of rocks, Clarke deduced that 99.22% were composed of 11 oxides, with the other constituents occurring in minute quantities.