Chinchaga fire

The Chinchaga fire, also known as the Wisp fire or the Chinchaga River fire, was a forest fire that burned in northern British Columbia and Alberta in the summer and early fall of 1950. With a final size of between 1,400,000 hectares (3,500,000 acres) and 1,700,000 hectares (4,200,000 acres), it is the single largest recorded fire in North American history. The fire was allowed to burn freely, a result of local forest management policy and the lack of settlements in the region. The Chinchaga fire produced large amounts of smoke, creating the "1950 Great Smoke Pall", observed across eastern North America and Europe. As the existence of the massive fire was not well-publicized, and the smoke was mostly in the upper atmosphere and could not be smelled, there was much speculation about the atmospheric haze and its provenance.

Background and cause

Chinchaga River in northern Alberta

The early spring of 1950 saw drought conditions develop in the boreal regions of northern Canada, especially in the watershed of the Chinchaga River.^[1] The region has a mix of black spruce, lodgepole pine and deciduous forests, giving way to muskeg in lower areas. Few people lived in the area in 1950.^[1]

Sources vary on the source of the fire but agree it was caused by human activity; one version faults an Imperial Oil surveying crew with starting a small blaze to protect their horses from biting insects.^[2] Other sources theorize that slash burning from agricultural clearing could have been the initial spark.^[1] The blaze started on 1 June 1950 and continued to burn throughout the summer and early fall until the end of October. The ignition point was north of Fort St. John, British Columbia, and the fire burned north-eastward nearly to Keg River, Alberta.^[1]

Burn

The path and extent of the burn was influenced by weather patterns. It burned in a fan-shaped pattern along a roughly SW/NE axis. The fire alternated between "runs" of rapid spread and high intensity, interspersed with periods of low activity. A series of high pressure systems over the summer allowed a buildup of heat and dry air, reducing the moisture levels in the forest fuels. The breakdowns of these systems produced the high northeasterly winds that drove the "runs".^[1]

There were five "runs" in total, with the final expansion in September 1950 causing the most destruction and amounting to one-third of the total burned area.^[1] Most of the burned area was on the Alberta side of the inter-provincial border, with only 90,000 hectares (220,000 acres) burned on the British Columbia side.^[3]

Size estimates have varied due to the imprecise measurement techniques of the time period. Estimates have ranged from 1,000,000 to 1,400,000 hectares (2,500,000 to 3,500,000 acres).^[1] In 2008 and 2009, researchers with Natural Resources Canada and the University of Victoria conducted airborne surveys of several boreal forest fires, including the Chinchaga. Utilizing polarimetric analysis, their final size was considerably larger than previous estimates, placing the total burned area at 1,700,000 hectares (4,200,000 acres).^[4] While most likely not the largest fire in the history of the North American boreal forest, it produced the largest burned area of any recorded fire on the continent.^[1]

No known deaths occurred as a result of the fire. In terms of damage, the dollar value of the Chinchaga fire is hard to estimate. Although sparsely inhabited, the area was a productive trapping area for First Nations and Métis. The timber of the Chinchaga River watershed had not been surveyed and was undervalued by the Alberta provincial government, which placed the fire's cost at one million dollars. Cordy Tymstra, an Alberta forestry department fire historian, said it is a "value that reflects how little officials appreciated the wealth of the land."^[2]

Response

No fire suppression efforts were directed at the fire. Fire crews were spread thin because of numerous blazes in B.C., the Yukon Territory and Alberta. At the time, the Alberta forestry department's policy was to respond only to fires within 15 kilometres (9.3 mi) of settlements and major roads.^[5] A request by the fire ranger at Keg River to fight the fire with a ground crew was denied by provincial fire managers.^[2]

"The Great Smoke Pall"

The Chinchaga fire produced large amounts of smoke, creating the "1950 Great Smoke Pall", observed across eastern North America and Europe.^[6] The giant smoke release from the conflagration in late September 1950 was first recorded at Ennadai Lake, in what is now Nunavut, on 24 September.^[6] The smoke was on a northeastern path, but hit an atmospheric trough and headed southward towards Ontario and the American eastern seaboard.^[6]

The province of Ontario experienced heavy smoke conditions, with the towns of Sarnia and Guelph experiencing three-hour midday periods of darkness, and the city of Toronto turning on its streetlights and automobile headlights during daytime hours. In Toronto power consumption increased by 200,000 kWh during the smoke event. Animals also felt the effects; cows required milking at different times, and birds were seen bedding down midday. Aircraft were grounded, and an aerial search for a downed United States military plane was delayed by the smoke.^[6]

Most of the smoke in eastern North America was born aloft by climatic conditions to high altitudes. As many observers could not smell it, and the news of the massive Chinchaga fire was sparse, affected people drew other conclusions about its source. Explanations included nuclear armageddon, local fires, supernatural forces, a solar eclipse and alien invasion.^[5][6]

The heavy haze moved on to the Atlantic seaboard of the United States. New York, Pennsylvania, Ohio, Washington D.C., Virginia and Florida all reported effects from the fire. As in Ontario, lights were turned on during the daytime, and animals showed abnormal behaviour.^[6] American meteorologist Harry Wexler followed the smoke plume closely, collecting data from a wide area of the U.S. He noted that the plume split in two during the event, with one southern plume getting caught in a stagnant anticyclonic pattern that extended the hazy period. Wexler observed lower temperatures as result of sunlight absorption by the smoke; he estimated a 4°C (6°F) drop in the Washington, D.C. area.^[6]

The northern smoke plume traveled over the Atlantic by way of Newfoundland and Greenland. On 27 September 1950, the plume was observed over Scotland, with reports over England following soon after. France, the Netherlands, Portugal and Denmark also observed the plume.^[1][2] Reports by pilots put the haze over Europe at 12 km (7.5 mi) or more in altitude, higher than observed in North America. In early October, a smoke observation was made on the Aleutian Islands, suggesting that the Chinchaga haze had possibly circled the entire globe.^[6]

See also

• List of wildfires

References