IS THEREA COMMON PATTERN?

摘要

In the 1980s, as the Alvarez hypothesis gained ground, it seemed reasonable to assume that all mass extinctions were caused by impacts. Though there have been numerous "discoveries" of craters and other impact signatures coinciding with the other mass extinctions, none has stood up to scrutiny. It now seems that the KT event was unique - the only mass extinction caused by an impact. In fact, we now think that each mass extinction had its own unique cause.