An enormous rifting occurred causing massive floods of basaltic lavas and the release of large amounts of gas this is thought to have been the cause of which mass extinction

In your lesson, you should be able to find this passage, "One possible cause of the End Triassic mass extinction is an enormous rifting event. It was the largest volcanic event in Earth's history. At the time, the present-day continents were part of a single super continent known as Pangaea. Across this continent, large rift zones were developing as Pangaea started to break up. The volcanism produced would have erupted massive floods of basaltic lavas and released large amounts of gas."

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Your answer is The answer is End triassic