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The
majority of fossils recovered in Cape Breton can be traced to
coal areas or coal fields. Fossils have been found ranging from
whole or partial tree trunks and branches to shrubs and vine
growth. Evolution dates back to pre-historic times - to approximately
325 million years ago when the region was covered in lush, dense
vegetation.
Coal beds consist of altered plant remains. When forested swamps
died, they sank below the water and began the process of coal
formation. However, more than a heavy growth of vegetation is
needed for the formation of coal. The debris must be buried,
compressed and protected from erosion. Even though all the biological,
geographic and climatic factors may be favourable, coal could
not be formed unless the plant debris was submerged and buried
by sediments.
There are four stages in coal formation: peat, lignite, bituminous
and anthracite. The stage depends upon the conditions to which
the plant remains are subjected after they were buried - the
greater the pressure and heat, the higher the rank of coal.
Higher-ranking coal is denser and contains less moisture and
gases and has a higher heat value than lower-ranking coal.
Peat - Stage One
Peat is the first stage in the formation of coal. Normally,
vegetable matter is oxidized to water and carbon dioxide. However,
if plant material accumulates underwater, oxygen is not present
and so only partial decomposition occurs. This incomplete destruction
leads to the accumulation of an organic substance called peat.
Peat is a fibrous, soft, spongy substance in which plant remains
are easily recognizable. It contains a large amount of water
and must be dried before use. Therefore, it is seldom used as
a source of heat. Peat burns with a long flame and considerable
smoke.
Lignite - Stage Two
Lignite, the second stage, is formed when peat is subjected
to increased vertical pressure from accumulating sediments.
Lignite is dark brown in colour and, like peat, contains traces
of plants. It is found in many places but is used only when
more efficient fuel is not available. It crumbles easily and
should not be shipped or handled before use.
Bituminous
Coal - Stage Three
Bituminous Coal is the third stage. Added pressure has made
it compact and virtually all traces of plant life have disappeared.
Also known as "soft coal", bituminous coal is the
type found in Cape Breton and is our most abundant fuel. It
is greatly used in industry as a source of heat energy.
Anthracite - Stage Four
Anthracite, the fourth stage in coal formation, is also known
as "hard coal" because it is hard and has a high lustre.
It appears to have been formed as a result of combined pressure
and high temperature. Anthracite burns with a short flame and
little smoke.
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