Nearly all meteorite impact craters on Earth are circular. Elongated crater structures are expected only at impacts at angles lower than 12 degrees from the horizontal. Kenkmann and Poelchau document the first elliptical crater on Earth that provides insights into the mechanisms of crater formation at low angles.
The diameter of the Proterozoic Matt Wilson impact structure (Northern Territory, Australia) is 7.5 by 6.3 kilometers, with its long axis trending northeast-southwest. The exposed crater floor shows a preferred stacking of thrust sheets within the central uplift, indicating a material transport top-to-southwest.
This is explained by remnant horizontal momentum transferred from the impacting projectile to the target rocks. The Matt Wilson structure provides evidence for the usefulness of structural asymmetries as a diagnostic tool to infer the direction of impact.
This study "Low-angle collision with Earth: The elliptical impact crater Matt Wilson, Northern Territory, Australia" by Thomas Kenkmann and Michael H. Poelchau, was published in the May 2009 edition of Geology.
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