The Dezadeash / Sakwak valley
and the Alsek Pass owe their U-shape to vast
glaciers that flowed outward from the Kluane
Icefield during the recurrent ice ages of the
last 3 million years. Valley-bound in the Alsek
River gorge, the massive Lowell Glacier, 65
kilometres in length has, over centuries, moved
up and down the river basin causing flood conditions
that have had far-reaching effects on vegetation,
animal populations, terrain and lifestyle of
the native people. In the past, surges of the
Lowell have actually dammed the Alsek River
to create lakes. In 1850, Recent Alsek Lake
drained in two days when the ice dam broke,
sending 40 cubic kilometres of water in a raging
torrent to the sea. Should Lowell surge again,
it could pose a potential flood risk to the
Alaska Highway.
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Fringing the glaciers and
mountains is a narrow Šgreen beltÆ of coniferous
and deciduous forests. In the river valleys
are the boreal forests of mainly white spruce.
On the lakebed of the drained Recent Lake Alsek,
grasslands gave way to willow and shrub and,
in time, balsam, poplar and trembling aspen
began a new forest where spruce would eventually
become dominant. At higher elevations of 1500
“ 1800 metres, alpine tundra and meadow grass,
herbs, shrubs and dwarf trees are home to woodland
caribou and DallÆs sheep.
The largest subspecies of moose in the world,
some weighing up to 800 kilograms, range through
the park's lower alpine region. Solitary
grizzly bears cross between alpine clearings
and vales. The Dall's sheep, the park's
most abundant large animal, numbers 4000. Woodland
caribou, mountain goat, black bear, wolverine,
lynx, red fox and wolf populations share the
landscape with the smaller muskrat, mink, marmot,
otter, beaver, snowshoe hare and squirrel. The
Arctic grayling, lake trout and pike abound
in lakes and streams. 118 of the 150 species
of birds observed in the park, such as the golden
eagle, bluebird and ptarmigan, come to build
nests and raise their young.
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