(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20110331/2007Z)
(3) Volcano:	Cleveland (VNUM #311240)
(4) Current Color Code:	UNASSIGNED
(5) Previous Color Code:	YELLOW
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2011/A1
(8) Volcano Location:	N 52 deg 49 min W 169 deg 56 min
(9) Area:	Aleutians
(10) Summit Elevation:	5676 ft (1730 m)
(11) Volcanic Activity Summary:	Based on a lack of confirmed eruptive activity over the past several months, AVO is downgrading the alert level and aviation color code to UNASSIGNED. Recent clear satellite views of the Cleveland summit show no significant thermal anomalies or evidence of recent explosive events such as ash deposits on snow. The last ash-producing event at Cleveland was in September 2010, when a small, very short-lived ash plume reached 25,000 feet above sea level. Since then, occasional periods in which thermal anomalies have been observed in satellite imagery suggest that low-level unrest has continued without any eruption of ash. The last weak thermal anomaly at Cleveland was detected early this morning. Daily reports on the volcano will cease. We wish to emphasize, however, that Cleveland Volcano experiences frequent episodes of low-level unrest; the summit crater at Cleveland often emits visible plumes of water vapor and possibly small quantities of volcanic gas. Heat associated with this process can produce occasional weak thermal anomalies detected by satellite; however, these do not always indicate eruptive activity has occurred or is imminent. AVO is unable to designate NORMAL/GREEN at Cleveland due to the lack of a seismic network to determine background levels of seismicity. Sudden, short-lived explosive events could occur without warning and send ash above 20,000 ft above sea level. These explosions could go undetected on satellite imagery for hours. AVO relies upon twice-daily satellite analysis of Cleveland, as well as pilot and mariner reports, to look for evidence of increasing activity or ash clouds.
(12) Volcanic cloud height:	No cloud observed.
(13) Other volcanic cloud information:	Nil
(14) Remarks:	Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 and it produced 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. The 2001 eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emission was in September 2010.
(15) Contacts:	John Power, Scientist-in-Charge, USGS jpower@usgs.gov (907) 786-7497 Steve McNutt, Coordinating Scientist, UAF steve@giseis.alaska.edu (907) 474-7131
(16) Next Notice:	A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at http://www.avo.alaska.edu

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AVO/USGS Volcanic Activity Notice

Volcano: Cleveland (VNUM #311240)

Current Volcano Alert Level: UNASSIGNED
Previous Volcano Alert Level: ADVISORY

Current Aviation Color Code: UNASSIGNED
Previous Aviation Color Code: YELLOW

Issued: Thursday, March 31, 2011, 12:07 PM AKDT
Source: Alaska Volcano Observatory
Notice Number: 2011/A1
Location: N 52 deg 49 min W 169 deg 56 min
Elevation: 5676 ft (1730 m)
Area: Aleutians

Volcanic Activity Summary: Based on a lack of confirmed eruptive activity over the past several months, AVO is downgrading the alert level and aviation color code to UNASSIGNED.

Recent clear satellite views of the Cleveland summit show no significant thermal anomalies or evidence of recent explosive events such as ash deposits on snow. The last ash-producing event at Cleveland was in September 2010, when a small, very short-lived ash plume reached 25,000 feet above sea level. Since then, occasional periods in which thermal anomalies have been observed in satellite imagery suggest that low-level unrest has continued without any eruption of ash. The last weak thermal anomaly at Cleveland was detected early this morning.

Daily reports on the volcano will cease. We wish to emphasize, however, that Cleveland Volcano experiences frequent episodes of low-level unrest; the summit crater at Cleveland often emits visible plumes of water vapor and possibly small quantities of volcanic gas. Heat associated with this process can produce occasional weak thermal anomalies detected by satellite; however, these do not always indicate eruptive activity has occurred or is imminent.

AVO is unable to designate NORMAL/GREEN at Cleveland due to the lack of a seismic network to determine background levels of seismicity. Sudden, short-lived explosive events could occur without warning and send ash above 20,000 ft above sea level. These explosions could go undetected on satellite imagery for hours. AVO relies upon twice-daily satellite analysis of Cleveland, as well as pilot and mariner reports, to look for evidence of increasing activity or ash clouds.


Recent Observations:
[Volcanic cloud height] No cloud observed.
[Other volcanic cloud information] Nil

Remarks:
Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 and it produced 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. The 2001 eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emission was in September 2010.

Contacts: John Power, Scientist-in-Charge, USGS
jpower@usgs.gov (907) 786-7497

Steve McNutt, Coordinating Scientist, UAF
steve@giseis.alaska.edu (907) 474-7131

Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at
http://www.avo.alaska.edu

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