[Above & Left]: Aerial picture and geological map of the meteoric impact crater at Ries in Germany. [Below]: Landsat image of crater at Talemzane in Algeria and 3-D modelling of same by Dr. Carlos Roberto de Souza Filho
These images come from the Earth Impact Database, which is currently managed by John Spray (Director, Planetary and Space Science Centre, University of New Brunswick, Canada..
The Earth Impact Database is maintained as a not-for-profit source of information to assist the scientific, industrial, government and public communities around the world in furthering our collective knowledge of impact structures on Earth. It is regularly updated with new discoveries.
The database is regularly updated with new discoveries but, to be included in the listings, the proposer must provide convincing evidence of shock features or impact formations, preferably in a published form. These rigid criteria help maintain the integrity of the data. [They have a long list of currently unproven impact structures, which they are planning to publish]
The FAQ shows two structures that look like meteor impact craters but are not – in Hudson Bay and Mauritania. Crater Lake, Oregon – often mistaken for an impact crater - is a caldera lake, the product of a St Helen’s style volcanic explosion.
There is a very interesting essay on impact craters on their site, based on a 1990 Scientific American piece by Grieves.
Our view of the importance of meteoric impacts has been radically changed in recent years by the findings from planetary exploration missions. This clearly shows that virtually all planetary surfaces are cratered from the impact of planetary bodies. It is now accepted that they have played a major role in reshaping the surface of Earth.
‘Most of the terrestrial impact craters that ever formed, however, have been obliterated by other terrestrial geological processes. Some examples however remain. To date, over 160 impact craters have been identified on Earth. Almost all known craters have been recognized since 1950 and several new structures are found each year.’
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