The second-largest mass extinction in Earth’s history coincided with a short but intense ice age. Although it has long been agreed that the so-called Late Ordovician mass extinction was related to climate change, exactly how the change produced the extinction has not been known. Now, scientists have determined that the majority of extinctions were caused by habitat loss due to falling sea levels and cooling of the tropical oceans.

Scientists say that recent drilling into the sediment of the Dead Sea indicates that it has recovered from several periods of dryness and very little rainfall in the ancient past, but warns that there’s still cause for concern.