The volcanic history of Ciomadul has been subdivided into an effusive phase that lasted until about 440,000 years ago and an explosive phase that began 200,000 years ago during which magma output increased 30-fold. Between 56,000 and 32,000 years ago, explosive activity occurred at Ciomadul. That timespan coincides with the deposition of tephra from volcanoes in Italy in Europe; it is possible that tephra also came from Ciomadul. Indeed, the age of Ciomadul's last eruption overlaps with the age of the Campanian Ignimbrite. Tephra from eruptions of Ciomadul has also bee found in the Ursului Cave of the Perșani Mountains. Some tephra layers found in two drilling cores of the Black Sea may have originated at Ciomadul.