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Ancient meteorite could have impact as Canada draws line in the Arctic

As they embark this week on a 42-day, bi-national seabed survey of the Arctic Ocean, Canadian and U.S. scientists aboard two government research vessels know they'll have to contend with bone-chilling polar storms, vast stretches of frozen sea and giant, ship-menacing icebergs that have broken free of the pack.

Bathymetric/topographic map of the Arctic Ocean and the surrounds But this year - the third straight summer in which geologists from the two countries will jointly probe the depths of the northern Beaufort Sea - they'll also be dealing another of nature's little challenges: a monster space rock big enough to rattle the entire planet, trigger tsunamis across the Arctic coasts of North America and Eurasia, shear off the top of a massive mountain chain and spread debris over hundreds of kilometres.

Fortunately, the meteorite in question did its damage about two million years ago after slamming into the submerged peaks of Alpha Ridge - a 2,000-km- long undersea mountain chain off of Canada's northernmost shores.

But the ancient object, believed to have struck Earth in the central Arctic Ocean about 300 kilometres beyond Ellesmere Island, may yet pose problems for this summer's Can-Am research mission as the experts try to profile a swath of polar sea floor that remains deeply disfigured from that prehistoric extraterrestrial impact.

And depending on what the surveyors find, Canada's quest for extended jurisdiction over undersea territory in the High Arctic - and its claims over a potential treasure house of offshore oil and other resources - could be helped or hindered by the old asteroid's enduring geological legacy.

Both Canada and the U.S. are trying to prove that parts of the Arctic seabed are really just extensions of the North American land mass, key to asserting political authority over those areas under provisions of the UN Convention on the Law of the Sea (UNCLOS).

That's why, this week, the U.S. Coast Guard cutter Healy and the Canadian Coast Guard icebreaker Louis S. St-Laurent are heading north for a Beaufort Sea rendezvous to continue the two nations' collaborative Arctic mapping mission in the shadow of Alpha Ridge.

The Arctic's sunken mountains are proving critical to offshore territorial claims being prepared by all polar nations. Canada, Denmark and Russia have each spent tens of millions of research dollars studying the Lomonosov Ridge that runs from Ellesmere Island and northwest Greenland, past the North Pole and over to central Siberia.

Russia has also pinned a major portion of its Arctic claims to the underwater Mendeleev Ridge that runs north of eastern Siberia and appears to link with the Alpha Ridge.

The case for gaining new undersea territory can be proven in one of two ways. Countries can claim seabed anywhere they can prove that the continental bedrock extends underwater from existing territory - Alaska for the U.S., the northern mainland and Arctic islands for Canada - until the sea floor drops consistently below a depth of 2,500 metres.

The other approach involves measuring offshore seabed sediment - such as the mountains of discharged silt accumulated at the bottom of the Beaufort Sea from the outlet of the Mackenzie River - and claiming continental extensions under a complex UN formula calculated from the depth of those deposits and their distance from shore.

The man in charge of mounting Canada's UNCLOS claims, Halifax-based Natural Resources geoscientist Jacob Verhoef, explains that the challenge is to gather evidence proving that vast swaths of Arctic seabed are ``natural prolongations'' of existing Canadian territory - ``in simple terms, attached to the North American continent.''

And he says the ancient Arctic meteorite strike - only recently theorized by an international team of scientists led by Norwegian researcher Yngve Kristoffersen - could have an impact on Canada's submission to the UN, due in 2013.

On one hand, the impact appears to have blown away a major chunk of the Alpha Ridge plateau - possibly dropping parts of the mountaintop below the 2, 500-metre threshold and complicating Canada's ``natural prolongation'' proof in the area.

``It could have an effect,'' Verhoef told Postmedia News, though he believes the ridge remains shallow enough to support Canada's claims over much of the region.

On the other hand, the material blasted away from peaks of Alpha Ridge appears to have settled in the Canada Basin - the deep undersea plain below the northern Beaufort, where Canada's case for territorial extensions will depend on the accumulation of sediment.

Could deposits of meteorite debris and other transported material from Alpha Ridge help Canada make its claim in that area?

``I think we may already have enough sediments - but the more the better,'' Verhoef says.

``We know that a lot of sediments have been deposited outside of Alpha Ridge to the northern part of the Canada Basin,'' he added. ``That's why we want to have a seismic survey line all the way up from the Canada Basin to the Alpha Ridge, right up through the centre of the deformed area.''

The U.S., too, is examining the impact of the proposed Alpha Ridge meteorite strike as part of its UNCLOS mapping efforts.

In June, a major report on polar science priorities - prepared by the U.S. Office of Naval Research and the U.S. Arctic Research Commission - identified the deformed sections of Alpha Ridge as key to unravelling mysteries about the geological origins of the mountain and crafting U.S. claims for new undersea territory.

``Currently, the prevailing opinion is that Alpha Ridge had an oceanic origin, but that it may have been modified by a large impact event,'' the report noted. ``Resolving the processes that formed Alpha Ridge is not merely an academic question; claims that the Alpha and Mendeleev ridges may be geologically linked have political and economic relevance, especially with sea ice cover diminishing, and increasing demand for oil, gas, and minerals, which exist in the Arctic.''

Author: Randy Boswell | Source: [August 02, 2010]


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