|(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)|
|(3) Volcano:||Cleveland (VNUM #311240)|
|(4) Current Color Code:||UNASSIGNED|
|(5) Previous Color Code:||YELLOW|
|(6) Source:||Alaska Volcano Observatory|
|(7) Notice Number:||2021/A950|
|(8) Volcano Location:||N 52 deg 49 min W 169 deg 56 min|
|(10) Summit Elevation:||5676 ft (1730 m)|
|(11) Volcanic Activity Summary:||A sustained decline in volcanic unrest at Cleveland volcano over the past few months has prompted the Alaska Volcano Observatory to downgrade the Aviation Color Code and Volcano Alert Level from YELLOW/ADVISORY to UNASSIGNED/UNASSIGNED.
Elevated seismicity, deformation within the summit crater, and thermal and gas emissions prompted raising the Aviation Color Code and Volcano Alert Level from UNASSIGNED/UNASSIGNED to YELLOW/ADVISORY on March 20, 2021. This activity continued over the summer, but all signs of unrest have ceased or declined in recent months. Elevated surface temperatures in the summit crater are still being observed at reduced frequency and strength. The last eruptive activity at Cleveland volcano was a short-lived explosion on the evening (local time) of June 1, 2020.
Despite the current pause, the eruptive period at Cleveland, dating back to 2001, remains ongoing and future explosions are likely. These occur without warning and typically generate small clouds of volcanic ash that are a hazard in the immediate vicinity of the volcano, though more significant ash emissions are possible.
Cleveland volcano is monitored with a limited real-time seismic network. This smaller network inhibits AVO's ability to detect precursory unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption may be possible using a combination of seismic, infrasound, lightning, and satellite data.
|(12) Volcanic cloud height:||not applicable|
|(13) Other volcanic cloud information:||not applicable|
|(14) Remarks:||Cleveland volcano forms the western portion of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. The volcano is located about 45 miles (75 km) west of the community of Nikolski, and 940 miles (1500 km) southwest of Anchorage. The most recent significant period of eruption began in February 2001 and produced 3 explosive events that generated ash clouds as high as 39,000 ft (11.8 km) above sea level. The 2001 eruption also produced a lava flow and hot avalanche that reached the sea. Since then, Cleveland has been intermittently active producing small lava flows, often followed by explosions that generate small ash clouds generally below 20,000 ft (6 km) above sea level. These explosions also launch debris onto the slopes of the cone producing hot pyroclastic avalanches and lahars that sometimes reach the coastline.|
|(15) Contacts:||Michelle Coombs, Scientist-in-Charge, USGS, firstname.lastname@example.org (907) 786-7497
David Fee, Coordinating Scientist, UAF, email@example.com (907) 322-4085
|(16) Next Notice:|