Brent Impact Structure
September 13, 2006
This photo illustrates a section of the “breccia lens” of fractured or shattered rock around the Brent Impact Structure in Ontario, Canada. Approximately 396 million years ago, a 150 meter diameter L or LL type chondrite meteoroid punched through our atmosphere impacting here at a velocity of between 12 and 30 kilometers per second. The resultant crater was 3.8 kilometers across, over 600 meters deep and with a rim over 100 meters high. The present floor of the crater is located 700 meters directly through the trees in the photo.
The high instantaneous pressure generated at impact created a lens of shattered rock around the bowl of the crater. Here a creek has eroded a small canyon through part of the exposed shattered rock. The shattered rocks visible on the “canyon” walls consist of Precambrian age consolidated rocks within the Grenville sub-province of the Canadian Shield. About 50 meters behind where I took this image, toward the crater rim, a small waterfall flows over the (non-shattered) bedrock. Photo taken in April of 2006.