Vancouver
Island was created as a result of the earth rising due to the pressure of the
Juan de Fuca plate and the Explorer Plate slowly travelling under the North
American plate in the Cascadia Subduction Zone.
For the same reason, this is one of the most earthquake prone areas in
Canada.
Large
‘megathrust’ earthquakes have historically taken place in the vicinity of Vancouver Island
approximately every 500 years.
Scientists believe that quakes of this type took place around 600 BC,
170 BC, 400 AD, 810 AD, 1310 AD, and in 1700 AD.
The
most recent megathrust quake took place on January 26, 1700 at 9:00pm. This time has been pinpointed due to the very
accurate timekeeping of the Japanese, who reported an ‘orphan’ tsunami (a tsunami
without a quake) that took place the following day.
The
1700 earthquake was estimated to have measured about 9.0 on the Richter scale,
and struck near the Canada border with Washington State.
Many
First Nations’ oral histories tell of this quake. The Nuu-chah-nulth on the West Coast of
Vancouver Island have stories that tell of a great quake that happened before
the first white men came. Some Coast
Salish tribes have stories that tell of a violent shaking of the earth that
went on for 20 hours (this likely includes aftershocks), made houses fall down,
and people on land get seasick.
A
Makah storey tells of great flooding which covered the land up to the trees for
four days. Other communities tell of
sand that shook until it swallowed things up.
Local First Nations have earthquake dances, which tell of the earth shaking.
The
effects of more recent earthquakes have been felt on Northern Vancouver
Island.
A 7.0
quake centered in the area near the Estevan Point Light Station woke up people
around the island at 12:41 am on December 16, 1918, but did not cause much
damage.
Damage to the highway near Sayward following the 1946 earthquake. |
A 7.3
quake in the mid-island area at 10:13am on June 23, 1946 knocked down 75% of
the chimneys in the Campbell River/ Comox area, and caused a soil failure that
ripped apart the highway near Sayward.
It has the distinction of causing the most recorded damage of any quake
on the island in historic times.
On
August 21 at 8:01PM in 1949 a strong 8.1 quake struck in Haida Gwaii which
reportedly knocked over cows near its epicentre, but this quake was not felt
strongly on the North Island.
A 9.2
quake in Alaska on March 27, 1964 caused a tsunami that hit many West Coast
communities. Most people are aware of
the damage that happened in Port Alberni, but a number of more northern
communities also felt its effects.
Damage in Zeballos after 1964 tsunami |
Hot
Springs Cove and Zeballos both reported a rising tide that would not stop
rising. The water kept coming until
almost every building was knocked off its foundations, and some floated some
distance.
The
Zeballos Iron Mine, which was on higher ground, served as a makeshift
shelter. Crew busses transported women
and children from the village to the mine camp, and cooks provided hot food for
the refugees.
Local
accounts told of massive churning of waters around Tahsis narrows killing
thousands of bottom fish, rapidly forced to the surface when their swim
bladders exploded.
In Port Alice an
airplane dock, mail wharf, and oil float were all damaged.
The
coastal float camps were largely able to ride out the tsunami. The tsunami occurred at a low tide, and
damage would have been much greater if the tide was higher at the time.
Another more local tsunami took place in
Knight Inlet around 1600 AD. First
Nations oral history tells of a massive landslide on the South side of the
channel, on the side of a mountain the First Nations knew as “Tohu.”
A landslide caused 3 – 4 million cubic
metres of rock to fall into the inlet to a depth of 500 metres. This caused a tsunami wave somewhere between
3 and 10 metres in height that travelled across the narrow inlet in less than a
minute, sweeping away the unsuspecting village of Kwalate.
The village was believed to have been home
to more than 100 people, with four chiefs, who were all lost in this tragic
event. A number of the victims were
recovered and were laid to rest near the entrance to Simoom Sound, and pictographs
of four coppers painted on the nearby rock were believed to commemorate the
event.
Archeological excavations found evidence of
the old village site, including middens and firepits under 1 metre of
overburden. Covering the village site
were tsunami deposits 1 – 5 cm deep, mostly of sand. The village was abandoned after this event,
and never recolonized. Today the event
is much studied by geologists, looking at the potential of tsunamis from above
and underground landslides.
Pictographs are not etched into rocks, that would be petrogylphs. I study the pictographs and petroglyphs of British Columbia and am not aware of 4 coppers etched or painted near the entance to Simoom Sound.
ReplyDeleteHey Ken- you're right they are pictographs. Here is a reference: https://www.tandfonline.com/doi/pdf/10.3137/ao.450205
ReplyDelete