Our Environment - Mining and the Environment: From Ore to Metal - page 298

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Till - comprising sediment from glaciers;

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Colluvium - soils transported by gravity, usually accumulating towards the base of a
slope;

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Eolian or windblown soils.

The term 'soil' has different
meanings in different branches of
science and engineering.

It should be recognized that the term 'soil' has different meanings in different branches
of science and engineering. The definitions presented above are those used by geologists.
However, unconsolidated marine or lake bed sediments are not included by geologists in
the definition of soils, despite having similar origins, compositions, and properties to other
transported sediments. Geotechnical engineers, however, use the term soil for unlithi-
fied natural materials, whatever their origin, and classify soils based on physical properties
of strength (cohesion and internal friction) as well as grain size. The agronomists have a
slightly different view of soils based on their suitability for agriculture, leading to the devel-
opment of completely different classification systems. These are particularly concerned with
profiles that develop as the parent material interacts with the climatic, hydrological, and
biological processes and the textural, drainage, moisture retention, and nutrient status of
different soil horizons.
Ores occur in igneous, metamorphic, and sedimentary rocks, although some rock types
are far more prospective for economic mineralization than others. Base metal and pre-
cious metal ores are commonly associated with volcanic activity, although this may have
occurred in the distant geological past, with only very subtle evidence of its origin. Residual
soils may also contain economic mineral deposits, the most notable examples being lateritic
ores of iron, aluminium, and nickel, which result from preferential leaching and enrich-
ment of particular metals under prolonged tropical weathering.
Clearly, geology influences most mining project activities and operations. Apart from
the composition and characteristics of the ore itself which influence the selection of exca-
vation, crushing, milling, and processing methods and equipment, the mine design is very
much influenced by geological structure, while the need for mine drainage or dewatering
will depend on the hydrogeology.

Base metal and precious metal
ores are commonly associated
with volcanic activity

Residual soils may also contain
economic mineral deposits,
the most notable examples
being lateritic ores of iron,
aluminium, and nickel, which
result from preferential leaching
and enrichment of particular
metals under prolonged tropical
weathering.

Landform

Landform is any physical feature of Earth's surface having a characteristic, recognizable
shape, influenced by geology and produced by natural causes as illustrated in Figure 7.3 .
Landforms can be broadly grouped into four categories (Pidwirny 2006):
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Structural Landforms are created by massive Earth movements due to plate tectonics
(e.g. fold mountains, rift valleys, or volcanos).

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Weathering Landforms are created by the physical or chemical weathering which
removes susceptible materials while leaving more resistant rock. Weathering produces
landforms such as mesas, hogback ridges 'breakaways' and karst features in limestone
such as pinnacles and sink holes.

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Erosional Landforms are formed from the removal of weathered and eroded surface
materials by wind, water, glaciers, and gravity (e.g. river valleys, glacial valleys, and
coastal cliffs).

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Depositional Landforms are formed from the deposition of sediment. These depos-
its may eventually be compressed, altered by pressure, heat, and chemical processes to
become sedimentary rocks (e.g. dunes, beaches, deltas, alluvial terraces, flood plains,
and glacial moraines).