11. The age of the impact event is uncertain. 12. This crater was formed following the Orientale impact event , and so is younger. 13. The Sudbury occurrence has been attributed to an impact event and associated crustal melting. 14. The meteorites cluster in families that seem to correspond to distinct impact events on Mars. 15. This became the first crater on Earth definitely proven to be from an impact event . 16. This sandstone has been fractured and brecciated by the impact event to form the rim. 17. Their presence therefore is a primary criterion for recognizing that an impact event has occurred. 18. Chapter 3 is about the process of formation of a crater during an impact event . 19. The lunar geologic timescale is based on the most prominent impact events , including stratigraphic horizon. 20. Current archaeological thought dates souterrains as late Iron Age, thousands after the supposed impact event .
