Geology Reference
In-Depth Information
Table 5.10 Constituents of groundwater from different rock
types. Concentrations in g=g (White et al., 1963)
Substance
Granite
Serpentinite
Shale
Cations or oxide
SiO
2
39
31
5.5
Al
9
0.2
0
Fe
1.6
0.06
3.5
Ca
27
9.5
227
Mg
6.2
51
29
Na
9.5
4
12
K
1.4
2.2
2.7
Anions
HCO
3
93
276
288
CO
3
0
0
0
SO
4
32
2.6
439
Cl
5.2
12
24
F
0
0
0
NO
3
7.5
6.8
0.9
PO
4
0
0
0
Around 10% of the Earth's surface is covered by glaciers ( 15:9 10
6
km
2
glacierised vs. 148:8 10
6
of total land surface (Knight, 1999)) of which 91%
span Antarctica, 8% traverse Greenland and the rest make up the final 1% (see
Table 5.11). If the rate of glacial melting is greater than the speed of accumulation,
the glacier recedes; if it is less, it advances. Many recent studies on glacier runoff
around the world have shown that the first possibility is the most likely, presumably
due to climate change. Glaciers are estimated to contribute to 0.6 to 1% of the global
annual runoff and current annual global glacial runoff ranges from 0.310
3
km
3
to
110
3
km
3
(Jones et al., 2002).
Table 5.11 Area of land surface covered by glaciers, together with esti-
mates of volume and the equivalent sea level rise that the volume implies
(Knight, 1999).
Area, km
2
Volume, km
3
Sea level equi-
valent, m
Region
Antarctica
13,600,000
25,600,000
64
Greenland
1,730,000
2,600,000
6
North America
276,000
Asia
185,000
Europe
54,000
200,000
0.5
South America
25,900
Australasia
860
Africa
10
Total
15,900,000
28,400,000
70.5
There are two types of glaciers: valley glaciers which are topographically re-
stricted, and ice sheets and ice caps which are not. Ice sheets, mostly found in
Antarctica and Greenland, cover expansive areas > 5 10
4
km
2
and ice caps typ-
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