Description: Several historical eruptions have been attributed to Isanotski, most notably the explosive March 10, 1825 eruption. However, according to Alaska Volcano Observatory geologists, Isanotski shows no evidence of having any possibly Holocene vents. Alaska Volcano Observatory geologists flying over Isanotski in 1997, 1998, and 1999 failed to find any apparently Holocene vents on Isanotski, and saw only glacially polished rocks. Geologists from AVO suggest that all historical eruptions of Isanotski instead be attributed to Shishaldin. Field investigations of Shishaldin reveal numerous Holocene vents, including a very large flank feature called "The Blister" that has melted through the modern ice cover of Shishaldin, and which could be the vent for eruptions during the 1800s. In addition, several streams draining from Shishaldin look capable of carrying large amounts of sediment to the sea (as described by Veniaminov for the March 10, 1825 eruption), but all of the streams draining Isanotski are heavily vegetated, suggesting that they did not carry large amount of sediment within the last few hundred years (Chris Nye, personal commun., 2004).
Coats (1950) lists Isanotski as "active" in 1845.