Earthquake in Labrador, Canada.

On Sunday 8 July 2012, slightly before 8.15 pm local time (slightly before 11.15 pm, GMT), an Earthquake struck in eastern Labrador, roughly 146 km south of Happy Valley, according to the United States Geological Survey, who measured the quake as 4.4 on the Richter Scale at a depth of 18 km. An Earthquake of this size is highly unlikely to have caused any damage or casualties, but would have been felt as severe shaking by anybody in the area.

The location of the 8 July 2012 quake. USGS.

Earthquakes in Labrador are extremely rare, making the cause of such quakes hard to determine. This is largest quake in the area since 1962. Eastern Canada is a long way from any active plate margins, the nearest being the Mid Atlantic Rift Zone, which runs through Iceland far to the east, and the subductive zone along the west coast of North America, far to the west. 

There are, however, a number of areas of tectonic stress in eastern Canada, one of which, the Lower St. Lawrence Seismic Zone, runs beneath the St Lawrence River, roughly 200 km southeast of the epicenter of the 8 July quake. This is hard to study directly, but seismic studies, which are based upon monitoring the way waves of energy from known quakes travel through the rocks below the region, enabling scientists to build a three dimensional image of the geological structure beneath the river in a similar way to sonar, suggest that this is caused by the reactivation of an ancient rift zone associated with the opening of the Iapetus Ocean in the Late Proterozoic to Early Paleozoic (i.e. roughly 500 million years ago).

Information from witnesses who felt quakes is extremely useful to scientists studying seismic activity. If you felt this Earthquake you can report it to Natural Resources Canada here.

See also Oklahoma shaken by Earthquake on Christmas Day, The dangers of a modern Laki style eruption in Iceland, Earthquake off the coast of Vancouver Island, Quebec Earthquake, 27 August 2011 and Earthquakes on Sciency Thoughts YouTube.

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Industrialization of the East Canadian Tundra blamed for 90% drop in Caribou numbers.

Caribou (Rangifer tarandus), or reindeer as they are known in the Old World, are ubiquitous Arctic herbivores, found from Northern Scandinavia across the Russian Arctic, Alaska, the tundras of Northern Canada and in Western Greenland. A former population in Eastern Greenland, that some scientists believe to have been a separate subspecies, was driven extinct in the nineteenth century (Caribou taxonomy is not clear; there are clearly several subspecies, but different authorities do not agree on how they should be defined). They are widely domesticated, both for their meat, and as a beast of burden, and wild herds are hunted by indigenous peoples across much of the Arctic. Because of the widespread domestication of Caribou the species is not in danger of extinction, but wild herds have suffered sharp declines in numbers in recent decades, something that has been widely blamed on increased human activity in the Arctic.

A Caribou on the Tundra of Quebec.

A study for the human rights group Survival International released last month, found that the world's largest wild Caribou herd, the George River Herd, which roams across the tundras of northern Quebec and Labrador, has fallen from around 800 000 in 1993 to about 74 000, a loss of slightly over 90% of the population. The Canadian Government has also been monitoring the herd, and has recently introduced tougher restrictions on reindeer hunting in the area.

The study by Survival International, which concentrates on witness statements from Innu Tribal Elders, does not see hunting as the main reason for the George River Herd's decline, but rather suggests the herd may have been effected adversely by increasing industrialization in the area, particularly extraction of iron ore from the Labrador Trough, a geological feature that runs across Labrador and Quebec, by mining company Cap-Ex Ventures and the rising number of road-building and hydro-electric projects in the area.

While this initially sounds persuasive, Caribou populations are naturally prone to severe population fluctuations. As recently as 1950 the total Caribou population for Labrador and Quebec was estimated to be as low as 5000, divided into two herds, the George River and the Leaf. These fluctuations are thought to be caused by the grazing habits of the Caribou. In good times the population of Caribou grows steadily, till there are more Caribou than the environment can sustain, then overgraze their food supply, leading to widespread starvation and a general population crash. This then allows the environment to recover, whereupon the Caribou numbers start to rise again. This is bad for individual Caribou, but not necessarily a bad thing for the species, as the periodic crashes weed out less fit individuals and serve to keep down predator numbers, be they wolves or hunting permits.

Obviously reducing the total grazing are available will reduce the maximum population size the herd can reach, and therefore bring about the population crash sooner, but it does not necessarily follow that a dramatic crash in Caribou populations can be completely attributed to human activity.

See also The Western Black Rhino and the Vietnamese Rhino declared extinct, Greenpeace activists occupy the offices of Cairn Energy and Mammals on Sciency Thoughts Youtube.