Alaska Volcano Observatory

On July 19, 2023, AVO raised the Aviation Color Code and Volcano Alert Level for Cleveland to YELLOW/ADVISORY, stating: "There has been an increase in the number of earthquakes observed near Cleveland volcano over the past week. Numerous earthquakes have been detected and 37 of these were large enough to be located by the local seismic network. Most of the earthquakes from early in the week located in the mid to shallow portions of the Earth’s crust, less than 11 miles (18 km) below the surface, while more recent earthquakes have been located at shallower depths, less than 4 miles (6 km) below the surface. These earthquakes are small (less than magnitude 2), but the frequency of events is unusual for Cleveland. These data along with satellite observations of elevated surface temperatures at the summit crater and continued gas emissions suggest an increased likelihood of a future eruption. In response, the Alaska Volcano Observatory is increasing the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY."
Over the next week, seismicity continued at elevated levels, and steam as gas plumes and elevated surface temperatures were detected at Cleveland (though the latter two are very common even when seismicity is at background levels). Then seismicity gradually declined through mid-August, and on August 25, the alert levels were reduced to GREEN/NORMAL.