AVERAGE COMPOSITION OF THE EARTH'S CONTINENTAL CRUST,
RIVERS, AND GROUNDWATER
|
ELEMENT or COMPOUND |
CONTINENTAL CRUST1 |
RIVERS2 |
GROUNDWATER2 |
|
Silica (SiO2) |
74.3 % |
10.9 % |
3.0 % |
|
Aluminum (Al) |
8.1 % |
< 0.1 % |
< 0.1 % |
|
Iron (Fe) |
5.1 % |
0.1 % |
< 0.1 % |
|
Calcium (Ca) |
3.6 % |
12.5 % |
11.2 % |
|
Sodium (Na) |
2.8 % |
5.3 % |
10.0 % |
|
Potassium (K) |
2.5 % |
1.9 % |
0.7 % |
|
Magnesium
(Mg) |
2.1 % |
3.4 % |
2.5 % |
|
Bicarbonate3
(HCO3) |
0.5 % |
48.7 % |
62.5 % |
|
Sulfate (SO4) |
< 0.1 % |
9.3 % |
10.0 % |
|
Chloride (Cl) |
< 0.1 % |
6.5 % |
5.0 % |
|
All other elements |
0.5 % |
1.4 % |
0.6 % |
1 Percentage of element or compound on a weight basis for
"average" continental
crust,
including igneous, metamorphic and sedimentary rocks.
2 Percentage of element or compound on a weight basis for the total
dissolved
solids in rivers or in groundwater.
3 Note that in crustal rocks, this compound
appears as carbonate (CO3)