On December 7, 2013 activity at Kizimen and nearby Kliuchevskoi significantly increased, continued during November 29 - December 7, prompting KVERT to raise the Alert Level to Red. Ash plumes rose to altitudes of 5.5-6 km (18,000-19,700 ft) a.s.l. and drifted more than 212 km NE and over 1,000 km E. According to a news article, a warning to aircraft was issued for the area around the volcanoes. Video showed gas-and-steam activity, and satellite images detected a daily weak thermal anomaly. On December 9, the Alert Level was lowered to Green when the eruptions stopped.