BRENT IMPACT CRATER – GROUND EXPLORATION – 5

2026 Ground Exploration of the Brent Impact Crater (fractured rock analysis)

In the spring of 2026, the Ottawa RASC undertook an expedition back into the Brent Impact Crater to make a detailed analysis of the “fractured rock canyon” that I discovered almost 20 years ago.

The 3.8 km diameter Brent Impact Crater was caused by a large meteorite impact 396 ± 20 million years ago, The energy release of the impact caused fracturing of the country bedrock that formed a bowl under the crater. The exposed lip of the bowl formed a rock wall around and within the crater rim .

Note how the “Fractured Rock” forms a bowl enclosing the crater with the fragments exposed immediately inside the crater rim.

The exposed fractured rock rim is illustrated here within the crater, with yours truly posted for scale. The crater rim is rising in the background. A small canyon in the wall of fractured rock was eroded here by a creek that revealed the fractured rocks.

From within the “canyon” I recovered a sample of the fractured mesoperthite country rock for study.

Shatter cones are distinct geological formations found only in the bedrock beneath meteorite impact craters or powerful underground nuclear explosions. Caused by extreme shock waves, they are the only macroscopic, unmistakable proof of a hypervelocity bolide strike on Earth.

The Manicouagan impact crater – shatter cone. Shatter-cones form in country rock from impact pressures of typically 2-10 GPa and up to ~30 GPa, and is the only distinctive and unique impact shock-deformation feature that develops on a megascopic scale (e.g., hand sample to outcrop scale).

Shatter cones are documented in very large impact sites, Manicouagan for example. A distinct crater size where shatter cones begin to form is not identified.

The mesoperthite rock sample I recovered at the Brent Crater suggests the beginnings of a shatter cone forming on the sample. Displayed is a cone with suggestions of striations. When the sample was embedded within the shattered rock mix, the cone pointed to the crater impact point.

My amateur hypothesis states that the Brent Impact Crater event approaches the energy required to form shatter cones. My documentation of the beginnings of the shatter cone effect on fractured country bedrock of the Brent Impact Crater might confirm this.

References:

BARATOUX, David and REIMOLD, Wolf Uwe. The current state of knowledge about shatter cones. Meteoritics & Planetary Science 51, Nr 8

French, Bevan M. 1998. Traces of Catastrophe, A handbook of Shock-Metamorphic effects, Lunar and Planetary Institute.

Grieve R.A.F. (1978) The melt rocks at Brent Crater, Ontario, Canada. Proc. Lunar Planet. Sci Conf 9th, pp. 2579-2608.

Grieve R.A.F. (1991) Terrestrial impact: the record in the rocks. Meteoritics, 26, 175-194

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