The posted co-ordinates will take you to an
information sign about the area, while the sign does not mention
the Slide itself, this is a suitable location to view the mountain
to the South from which the debris came to create this now
spectacular area.
Landslides:
Every year many slides occur in our Province, in the
rest of Canada and throughout the world, some are merely water
saturated banks which slip down a hillside, others are rock and
debris which may originate near mountain peaks and can range from
small events to large amounts of material moving down the
mountainside. Some are the result of man's interference in the
makeup of the landscape, (i.e. road building) most, happen due to
minor or major natural events, as nature continually reshapes our
land surfaces. Some we see, others occur in remote areas and may be
seen occasionally from the air, or in some cases, not at all. The
fact that these events occur and have occurred over millennia is
recognized in this Earthcache.
Types of Landslides:
The graph below shows the common types of slides, try to guess what
type of slide might have occurred that created the division of the
lake and what we see here today.
How it might have happened:
With a thunderous
roar, a large piece of the mountain broke off and tumbled in a
giant cascade of rocks, shale and other debris, into the valley and
lake below. Like a broken dam, the seemingly endless torrent poured
on and on. When the last vibrations had finally died away, a great
wall of broken rocks stretched form one side of the valley to the
other, and there were two lakes instead of one.
Thus was born the land area between Anderson and Seton Lakes, known
today as Seton Portage. From a hillside view one can see clearly
the great cavity in the mountain from which the slide emerged, and
the contours of the slide itself, from the mountain base to the
extended thrusts on the far side.
We do not know if human eyes ever witnessed the great havoc that
changed forever the geography of this mountain valley. Hundreds, or
even thousands of years of wind, snow and rain have settled the
rocks and gradually ground them into earth. Vegetation grew and
covered the ugly scars, as is the way of nature, and the Portage
became a place o beauty.
Everywhere great rocks and boulders lie close to the surface,
covered more deeply in places by river silt. Streams from the
mountainside and upper lake worked their way through the rocks, and
gradually a river joined the two lakes. Smaller Slides blocked its
course many times so that it had to break through new channels.
There are at least six old river beds visible on the Portage today.
Though well established in its present bed, Seton Portage River is
threatened by small slides from time to time.
Through the years the two lakes have become strangely different,
Anderson Lake is a deep blue, but the lower Seton Lake, fed from
glacier silted streams, and waters from the Bridge River Dams, has
become green. Sometimes it has a pale chalky appearance, but after
the spring floods, it settles to a beautiful jade green - truly a
beautiful gem in its mountain setting.
The fact that these two lakes were once "one" has been corroborated
by the Dept. of Geology in Victoria. The big slide could have
happened as far back as 10,000 years ago. Many rocks and mud slides
occur year after year, building up the land
portion.
The last complete blockage occurred in 1907. Lillooet residents,
noting that the level of Seton Lake and the creeks were lowering
rapidly, went up by boat to investigate. They found the Seton
Portage River blocked completely by a huge slide, and its waters
flowing back into Anderson Lake. The spring freshet's soon broke
through the slide again, and a new river channel was
formed.
Seton Portage Earthcache identifies the
monumental landslide which occurred long before this area had even
been visited by any white man. In all three pictures on this cache
page you can identify the cavity which remains on the side of the
mountain to the left in each picture from where the rock and debris
came.
Prior to the side of the mountain collapsing into
what once was one large lake and thereby creating two lakes, now
known as Anderson Lake and Seton Lake (The uppermost lake in the
pictures is Anderson Lake )the area was most likely occupied by
First Nations peoples. It would be assumed that those who were in
the valley or even on the lower mountainsides anywhere in this
valley were swept away with the enormous tsunami created when
the rock, earth and other debris entered the lake. Over the years
since the slide, First Nations peoples and others resettled the
area as it became a rich and fertile land with abundant wildlife
and berries. Today there are approximately 500 First Nations
Peoples living in the area of the Portage.
NOTE: On some maps the river joining
Anderson and Seton Lakes is identified as Seton
River
In order to log this earthcache you
must:
1) View the mountain from which the event occurred
and e-mail the owner with your guess as to what type of slide you
think took place to cause this now beautiful area. Also identify at
least 2 other types of slides. There are several landslide types
and since we don't really know the exact cause of this slide, we
are left to guess at it's most likely cause. Two other significant
historical slides have occurred in British Columbia, do you think
they were the same or a different "type". .
2) Email the owner with the date that is
displayed on the Informational Sign at the Posted
Co-ordinates.
3) Optional Bonus: Post a picture of yourself with
your gps at the Portage, either near the outflow of Anderson Lake
or somewhere along the river which joins the two
lakes.
| I have earned GSA's
highest level: |
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