evidence: "For years, people suggested there would have been a decrease in ocean pH because the meteor impact hit sulphur-rich rocks and caused the raining-out of sulphuric acid, but until now no one had any direct evidence to show this happened," said lead author Michael Henehan, a former Yale scientist who is now at GFZ German Research Centre for Geosciences in Potsdam, Germany. [...] The new study also may have settled a question regarding ocean pH levels leading up to K-Pg. Some researchers have theorized that volcanic eruptions starting hundreds of thousands of years before K-Pg had progressively made Earth more prone to a mass extinction event. This should be reflected in a steady decline in ocean pH levels up until the extinction. "What we can show is that there is no real signal of gradual pH decline in the ocean in the lead-up to K-Pg," Henehan said. "Our results do not support any major role for volcanic activity in priming the world for extinction."