Worldwide volcanism coincident with the end of the Cretaceous provides the source of iridium, shocked minerals, the carbon (CO ₂) excursion, and the attendant greenhouse effect (from ¹⁸O data). Reproductive stress under greenhouse conditions may have been a deciding factor in extinction of terrestrial fauna. Acidification of the upper ocean due to volcanic CO ₂may be the responsible factor in the K/T nannoplankton event. The K/T transition is characterized by extensive paludification, forming bryophytic bogs, the source of K/T coal beds. Mantle convection is deemed the source of the worldwide volcanism attending the Late Cretaceous. Episodic mantle convection may have been responsible for other extinction events.