by: Charles O’Dale 

The age spectra corrected for the trapped argon component and inverse isochron plots consistently yielded ages around ~460–470 Ma for ECL, reproducing the Ar/ Ar results by Bottomley et al. (1990) and contradicting an earlier Rb–Sr age of 287 ± 26 Ma. The Ar-Ar dates obtained from four different melt samples across the melt sheet favor an Ordovician age for the East Clearwater Lake impact and impact-induced hydrothermal overprint.


The Rock Elm structure imaged from my chariot GOZooM from 5000 AGL.

The Merewether (possible) impact crater – looking south from my chariot GOZooM.

40 Ar/39 Ar age of the Lake Saint Martin impact structure (Canada) – Unchaining the Late Triassic terrestrial impact craters

Martin Schmieder, Fred Jourdanb, Eric Tohvera, Edward A. Cloutisc

The Earth is immersed in a swarm of Near Earth Asteroids (NEAs) capable of colliding with our planet, a fact that has become widely recognized within the past decade. The first comprehensive modern analysis of the impact hazard resulted from a NASA study requested by the United States Congress. This Spaceguard Survey Report (Morrison 1992) provided a quantitative estimate of the impact hazard as a function of impactor size (or energy) and advocated a strategy to deal with such a threat. (Morrison 2007)

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  • Touchwood Hills, Saskatchewan  – AprilTouchwood Hills Provincial Park, Saskatchewan – a very large circular structure with Last Mountain Lake to the west and Quill Lakes to the north. These arcuate lakes “may” be resting on the rim of a large impact structure.(RADARSAT-1 Mosaics).

“We, all of us, are what happens when a primordial mixture of hydrogen and helium evolves for so long that it begins to ask where it came from.”

Jill Tarter