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#           Photogrammetric monitoring of lava dome growth during the 2009 eruption of Redoubt Volcano      

      January 1, 2013    

The 2009 eruption of Redoubt Volcano, Alaska, began with a phreatic explosion on 15 March followed by a series of at least 19 explosive events and growth and destruction of at least two, and likely three, lava domes between 22 March and 4 April. On 4 April explosive activity gave way to continuous lava effusion within the summit crater. We present an analysis of post-4 April lava dome growth using an oblique photogrammetry approach that provides a safe, rapid, and accurate means of measuring dome growth. Photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed-wing volcanic gas surveys produced a series of digital elevation models (DEMs) of the lava dome from 16 April to 23 September. The DEMs were used to calculate estimates of volume and time-averaged extrusion rates and to quantify morphological changes during dome growth.

Effusion rates ranged from a maximum of 35 m3 s− 1 during the initial two weeks to a low of 2.2 m3 s− 1 in early summer 2009. The average effusion rate from April to July was 9.5 m3 s− 1. Early, rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater. In mid-to-late April the volume of the dome had reached 36 × 106 m3, roughly half of the total volume, and dome growth within the summit crater began to be limited by confining crater walls to the south, east, and west. Once the dome reached the steep, north-sloping gorge that breaches the crater, growth decreased to the south, but the dome continued to inflate and extend northward down the gorge. Effusion slowed during 16 April–1 May, but in early May the rate increased again. This rate increase was accompanied by a transition to exogenous dome growth. From mid-May to July the effusion rate consistently declined. The decrease is consistent with observations of reduced seismicity, gas emission, and thermal anomalies, as well as declining rates of geodetic deflation or inflation. These trends suggest dome growth ceased by July 2009. The volume of the dome at the end of the 2009 eruption was about 72 × 106 m3, more than twice the estimated volume of the largest dome extruded during the 1989–1990 eruption. In total, the 2009 dome extends over 400 m down the glacial gorge on the north end of the crater, with a total length of 1 km, width of 500 m and an average thickness of 200 m.

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#### Angie Diefenbach

##### Volcanologist - VDAP

Volcano Hazards Program

##### VSC UAS Project Lead

Cascades Volcano Observatory

adiefenbach@usgs.gov

360-993-8957

#### Rick L. Wessels, Ph.D.

##### Volcano Geophysicist

Volcano Science Center

rwessels@usgs.gov

## Related Content

#### Angie Diefenbach

##### Volcanologist - VDAP

Volcano Hazards Program

##### VSC UAS Project Lead

Cascades Volcano Observatory

adiefenbach@usgs.gov

360-993-8957

#### Rick L. Wessels, Ph.D.

##### Volcano Geophysicist

Volcano Science Center

rwessels@usgs.gov

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#### USGS Volcano Science Center

1300 SE Cardinal CourtVancouver, WA38683United States

360-993-8900

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