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RE: Arctic Asteroid Impact
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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.
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.

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Alpha Ridge Impact Structure
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Title: Evidence of an Asteroid Impact in the Central Arctic Ocean?
Authors: Hall, J. K.; Kristoffersen, Y.; Coakley, B. J.; Hopper, J.; Seismic Team, H.

Revaluation of single channel seismic reflection data from ice station T-3 (1967-74) acquired over the submarine Alpha Ridge in the central Arctic Ocean, supplemented by new multi-channel data, show spatially restricted massive disturbance of sub-bottom sediments within a 200 x 600 km area. Deposits have been locally disrupted down to at least 500 meter below the bottom, and have suffered intensive local erosion. Mass wasting is abundant. At this point, we are not able to neither document a likely cause for each of these types of stratigraphic disturbance nor a direct relationship between them. However, we note that: 1) tectonic movements normally involve the whole stratigraphic column and are not depth limited as observed here; 2) ground motion may trigger mass wasting, but is less likely to generate intense bottom current erosion; and 3) enhanced bottom currents are basin-wide phenomena and only disrupt stratigraphic continuity down to the deepest erosion level. As a working hypothesis, we suggest the spectrum and scale of drastic, spatially restricted and apparently geologically short-lived environmental changes are best explained by the effect of a shock wave from impact of an extra-terrestrial body into the central Arctic Ocean, the T3-Healy asteroid. The timing of an impact is unknown, but may be ?Plio-Pleistocene.

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But this yeará -á 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.

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Arctic Asteroid Impact
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alpharidge2b.gif
Expand (112kb, 560 x 345)

Credit 2005 seismic team

Latitude:á 84░29'41.47"N, Longitude: 102░34'12.04"W

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Title: Extensive local seabed disturbance, erosion and mass wasting on Alpha Ridge, Central Arctic Ocean: possible evidence for an extra-terrestrial impact?
Authors: Yngve Kristoffersen, John K. Hall, Kenneth Hunkins, JosÚ Ardai, Bernard J. Coakley, John R. Hopper & Healy 2005 seismic team

Sub-bottom sediments within a 200 x 600 km area on the crest and south slope (water depth 1200-2500 metre) of the submarine Alpha Ridge in the central Arctic Ocean have been locally disrupted down to at least 500 meter below the seabed, suffered intensive local current erosion, and abundant mass wasting. There appears to be a westward progression along the ridge from an eastern area of chaotic and eroded sub-bottom sediments to proximal intense erosion of an undisturbed section and a more distal occurrence of mass wasting and minor erosion. As a working hypothesis, we propose that the spectrum and scale of drastic, spatially restricted and apparently geologically short-lived environmental changes are compatible with the effect of a shock wave from the impact of an extra-terrestrial body into the central Arctic Ocean.

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Hunting Arctic Asteroid Impact With Hovercraft
Two polar scientists hot on the trail of an arctic mystery have a new tool for exploration: a hovercraft, specially outfitted for week-long trips over the ice with scientific instruments and solar panels.
Their quarry is a nearly 22,000 square-mile patch of disturbed Arctic sea floor that could be evidence of a massive asteroid strike. John Hall, a now-retired geoscientist, discovered the anomaly during his late-60s graduate work aboard Fletchers Ice Island, a huge berg U.S. scientists inhabited for several decades.

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See also Ancient Arctic Impact

Single channel seismic reflection data from ice station T-3 (1967-74) acquired over the submarine Alpha Ridge in the central Arctic Ocean, supplemented by new multi-channel data, show spatially restricted massive disturbance of sub-bottom sediments within a 200 x 600 km area.
The timing of an impact is unknown, but may be Plio-Pleistocene.


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