At the end of the Cretaceous what unusual geologic phenomenon occurred that has likely been linked to mass extinction and the end of the dinosaurs?
1) the climate abruptly warmed and massive weathering of iridium poisoned the seas
2) dinosaurs were hunted to extinction by Klingons
3) a 10 km meteor impact occurred on the Yucatan peninsula
4) enormous outpourings of basaltic lavas built the Rocky Mountains in British Columbia