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The intense energy accumulated
as water rages, bubbles and flows down a stream is drastically
dampened when the water enters a calm lake or quiet ocean bay.
As the speed of the flow slows rapidly, its ability to move sediment
is also hampered. The water belches out its load in the form
of a delta, so-named because the deposit can develop a crudely
triangular shape that resembles the Greek letter "delta."
Sediments are deposited by weight: the heavy, coarse sediment
drops out near the input, while lighter sediments fan out away
from the mouth of the river.
River deltas have long been of fundamental importance to human
settlements. A delta is often the continuation of a floodplain
-- its front so to speak -- and therefore harbours fairly fine,
clay-like sediment. Where flood control and drainage have been
established, delta sediments have provided fertile agricultural
land.
More recently, large petroleum reservoirs contained within
the deep ground that underlies deltas have contributed to the
world's energy needs. The sedimentation of organic matter in
ancient deltaic sediments has provided reservoirs for a significant
portion of known petroleum reserves.
The Mackenzie River Delta
Located in the northwest corner
of the Northwest Territories, along Mackenzie Bay, the Mackenzie
Delta is inundated with off-shoots of the Mackenzie River, as
well as numerous lakes and ponds. Aside from its unique watery
landscape, the delta also has other redeeming qualities.
The delta is home to the world's largest concentration of
pingos
-- with about 1,450. Pingos are large, volcano-shaped mounds
of solid ice, which are thrust up through the permafrost terrain
by the growth of their ice cores from below.
The Mackenzie Delta also provides one of the greatest wildlife
habitats in the world. Numerous small and large land mammals
live here, and millions of birds nest in the delta during the
summer. Swans, cranes, geese, eagles, hawks and falcons are but
a few that flock to the region.
Oil and gas refineries have become part of the delta's landscape.
Promises of an estimated 1.5 billion cubic metres of oil and
2.1 trillion cubic metres of natural gas have fuelled the industrial
development of the territory's northern shore along the Beaufort
Sea.
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