|Shatter Cone from the Sudbury Basin.|
In 1992 I attended a conference on Large Meteorite Impacts and Planetary Evolution in Sudbury, Ontario. The highlight of the visit was the field trip that we took to view the geological evidence of a massive meteorite impact nearly two billion years ago. The impacting object was likely in the range of 10-15 km (about 1/2 - 1 mile) in diameter. It left an oval basin which is 60 by 30 km (40 by 20 miles) containing breccia, a rock formed from the broken fragments of pre-impact bedrock. There are also rocks that have been shattered by the shock wave from the impact. These are only found in impact craters and are called shatter cones.