2009 Mount Redoubt Eruptive Activity - Eruptive Activity

Eruptive Activity

As of April 4, 2009, AVO had recorded twenty-six volcanic eruptions and/or explosions at Redoubt volcano, although they singled out nineteen of them as most notable. The AVO refers to an "eruption" as any event which discharges ash into the atmosphere, while adding the term "explosion" for more vigorous events. The AVO did not rate and compare each eruption, although the 9:24 am eruption on March 26 reached an altitude of 65,000 feet making it the highest volcanic ash cloud to date during the 2009 phase of activity. The eruption on April 4 was described as being the biggest eruption to date. There were also periods when the volcano emitted notable amounts of steam but did not erupt.

The AVO reported that Redoubt erupted or exhibited other notable activity at the following times, with all ash cloud heights in feet above sea level:

• March 15 01:00 pm First emissions of steam and ash to occur before the first major eruptions began on March 22.
• March 22 10:38 pm
• March 22 11:02 pm
• March 23 12:14 am
• March 23 01:39 am
• March 23 04:31 am
• March 23 07:41 pm
• March 25 05:12 am
• March 25 10:17 am
• March 26 08:34 am
• March 26 09:24 am Ash cloud reached 65,000 feet
• March 26 11:47 pm
• March 27 08:40 am
• March 27 05:35 pm Ash cloud reached 40,000 feet
• March 27 07:25 pm Ash cloud reached 51,000 feet
• March 27 11:20 pm Ash cloud reached 41,000 feet
• March 28 01:20 am Ash cloud reached 50,000 feet
• March 28 01:40 pm Ash cloud reached 25,000 feet
• March 28 03:29 pm Ash cloud reached 35,000 feet. Tephra from this event fell in Anchorage and Valdez.
• March 28 07:23 pm Ash cloud reached 45,000 feet
• March 29 + 30 11:23 pm – approx. 3 am Ash reaching under 25,000 feet. Preceded by an unrelated magnitude 5.4 earthquake near Kodiak.
• March 30 09:44 am Ash cloud reached 27,000 feet. Small, continued ash eruption with related tremor ended after approx. 10 minutes
• March 30 10:40 am Nearly continuous ash cloud reached 20,000 feet.
• March 30 11:26 pm Ash cloud reached 25,000 feet. Strong thermal anomalies suggest a new lava dome is growing at the summit.
• March 31 04:07 pm Ash cloud reached 25,000 feet
• March 31 – April 4 Mount Redoubt emitted a nearly continuous plume of steam, ash and gas at low levels. This was a continuation of the March 31 event and not new activity.
• April 4 05:58 am Ash cloud reached 50,000 feet. A related lahar flooded the Drift River Valley and damaged a generator facility at the nearby tank farm. The ash cloud drifted southeast and left a heavy coating of tephra on portions of the Kenai Peninsula. This has been described as the largest eruption to date during the current cycle, although it did not create the highest plume.
• Since April 4, Mount Redoubt has remained in a constant state of mild eruption and dome building at its summit. The Alaska Volcano Observatory warns that more a more vigorous eruption may occur at any time, possibly due to a potential collapse of the new dome. In late May, 2009, activity decreased and the Alaska Volcano Observatory lowered the alert level.
• A nearly six-month period of relative quiet at the volcano ended on December 27, 2009, with renewed earthquake swarms. The AVO subsequently raised the alert level, and again warned of the possibility of a more vigorous eruption due to dome collapse.