Tuesday, April 04, 2006

Earthquakes in Canadian Arctic

March 31, 2006

Global warming means more earth tremors in polar regions

JANE GEORGE

Puvirnituq residents were terrified by a small earthquake that struck their community last Wednesday at about 5 p.m., creating an explosive noise that sent people running outside their homes.

There were no reports of injuries or serious damage.

Four or five quakes of similar intensity strike eastern Canada each year, although scientists now say earthquakes are on the rise in some areas of the Arctic, and that some of these may be associated with global warming.

The recent increase in the number of “glacial earthquakes” supports the idea that Greenland’s glaciers and its ice sheet are melting.

Glacial earthquakes occur as enormous ice-sheets melt away, so that the weight on the land is removed and the ground rises. When certain areas rise faster than others, the difference causes tearing and grinding deep in the ground, triggering earthquakes.

The annual number of glacial earthquakes recorded in Greenland is rising, says a study, published March 24 in the journal Science.

From 1993 to 2002, there were between six and 15 a year, but in 2003, earthquake scientists — or seismologists — recorded 20 glacial earthquakes. In 2004, they recorded 24; and, for the first 10 months of 2005, they recorded 32.

The seismologists also found that glacial earthquakes occurred mainly in summer months, which suggests these movements are associated with rapidly melting ice. Normal earthquakes occur at all times of the year.

Nunavut and Nunavik are already among the most earthquake-prone zones in Canada. According to data gathered by the Geological Survey of Canada, the northeast coast of Baffin Island and the High Arctic islands have a particularly high incidence of earthquakes.

Over the past 80 years, nearly 2,000 earthquakes have been recorded in Nunavut. Over the past 10 years, there have been on the average about 40 earthquakes per year in the territory.

Most are minor, and fall below magnitude 4.0 on the Richter Scale, which is used to measure the intensity of earthquakes. These light earthquakes may make a low rumbling noise, but they produce little movement of the ground.

Over the past month, there have been earthquakes recorded in Repulse Bay, Chesterfield Inlet, Qikiqtarjuaq, Resolute Bay, Kugaaruk, Arctic Bay and Clyde River. The most powerful registered 3.3 on the Richter scale and occurred on Feb. 26 near Pond Inlet.

On Nov. 20, 1933, a monster earthquake ripped through the sea-floor of Baffin Bay, not far offshore from Pond Inlet. Seismologists believe its magnitude measured 7.3 on the Richter scale. A quake that powerful can hurl people to the ground, shake buildings apart, set off landslides and trigger giant tidal waves.

In 1989, on Nunavik’s Ungava Peninsula, a magnitude 6.3 earthquake tore open the tundra and shook up surrounding communities. The earthquake shattered stone, partially drained one lake, and created a new lake where none had previously existed.

Last week’s earthquake in Puvirnituq registered at 4.0.

For artwork from the Canadian Arctic region including Nunavut and Nunavik, see Free Spirit Gallery Inuit Arctic Art.

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