Environmental Engineering Reference
In-Depth Information
Ice
Ice
BS
T
IB
OP
D
C
IML
Ice
T Tunnel
BS Broided stream
OP Outwash plain
IB Ice blocks
IML Ice marginal lake
C Crevasse
D Delta
TM Terminal moraine
D Delta
LP Lacustrine plain
OP Outwash plain
KL Kettle lakes
GM Recessional moraine
IM Interlobate moraine
GM Ground moraine
E Esker
KT Kame terrace
DR Drumlins
CF Crevosse filling
FIGURE 7.77
Schematic diagrams to suggest the modes of origin of some of the more common glacial landforms. (Drawing
by W. C. Heisterkamp, from Thornbury, W. D., Principles of Geomorphology , 2nd ed., Wiley, New York, 1969.
With permission.)
7.6.2
Till
Origin
Referred to as glacial till or ground moraine, till is material dropped by the ice mass as the
slow pressure melting of the flowing mass frees particles and allows them to be plastered
to the ground surface.
Lithology
General
Till is a compact, nonsorted mixture of particles that can range from clay to boulders, and
bears less or no evidence of stratification, as shown in Figure 7.78. Its lithology is normally
related to the bedrock type of the locale, since continental glaciers apparently do not as a
rule carry their load over great distances, although boulders have been found hundreds of
miles from their source.
Materials
Tills are described as clayey, sandy, gravelly, or bouldery, and in the clayey phases are
referred to as “hardpan,” “boulder clay,” or “gumbotil.” In areas of granite rocks, the till
 
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