Environmental Engineering Reference
In-Depth Information
40
10
6
Tectonic
Tectonic
30
10
4
20
10
2
10
10
0
0
0.01-0.1
0.1-1
1-10
10-100
102-103
103-104
104-105
105-106
40
10
6
Glacial
Glacial
30
10
4
20
10
2
10
10
0
0
0.01-0.1
10-100
10
4
-10
5
6
10
6
Fluvial
Fluvial
4
10
4
10
2
2
10
0
0
Surface area range (km
2
)
FIGURE 6.5
Global numbers and total areas of lakes of different geological origins by sur-
face area size class (data from Meybeck, 1995).
leys. One of the strangest lakes associated with glaciers is the gigantic lake
that has recently been described below the ice in Antarctica (Sidebar 6.1).
As glaciers move, they entrain rocks and sediments into the ice. Where
glaciers melt at the edges and front, they deposit these materials. As the glac-
iers retreat they leave this material, called glacial till, behind. If large blocks
of ice remain in this till, they melt and eventually leave lakes, ponds, or wet-
lands called
kettles
or potholes (Fig. 6.7). This process formed the many
lakes and ponds that provide vital habitat to waterfowl in the northern
Olkhon Island
Fault
Lake surface
0
1
0 - 1.7 million
year old sediment
2
3
4
3.5 - 35 million
year old sediment
5
Bedrock
6
0
1
2
3
4
5
6
7
8
9
Width (km)
FIGURE 6.6
Cross section of Lake Baikal, the south basin, in the region of maximum depth
(1620 m) [redrawn from Belt (1992) and Mats (1993)].
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