ERUPTION ALERT – November 2011 eruption of Nyamulagira
Information report n°5 – 15th November, 2011
On 6th November 2011, 5:55 PM (UTC+2), Nyamulagira volcano has started to erupt after two days of intense seismic activity. This eruption is located ± 12 km east-northeast of the Nyamulagira crater, close to one of the 1989 eruptive sites. The previous eruption of this volcano occurred 22 months earlier, in January 2010. The eruptive fracture is oriented approximately East-West, perpendicularly to the rift direction.
Information from optical satellite imagery
ASTER, Hyperion and ALI images were acquired on November 12 and allow for the first time estimating the length of the lava flow. Within 6 days of eruption, the lava flow reached 11.5 km long. The path followed by lavas corresponds to the most western one suggested by the lava flow simulations (Fig. 2 and 3). On November 12, the lava flow front was located 5 km far from the road Kelengera-Tongo. According to the lava flow simulations, this road could be threatened by the lava flow.
Information about ground deformations
Satellite radar images acquired on November 11 revealed major ground deformation features associated to the eruption. It is actually the largest deformation ever detected by that method (InSAR) since the early 1990’s over that volcano.
Very preliminary estimation of the observed deformation signal suggest an affected area spreading over much more than 250 km2.
Under the pressure of the ascending magma, the ground rose up to more than 50 cm at the eruptive site where the spatter cone is developping. Another 15 cm deformation is detected within the Nyamulagira caldera accompanied with a deflation observed on the flanks. In contrast, no apparent deformation can be noticed on Nyiragongo until that image acquisition.
More detailed analysis is under way and additionnal satellite images are due for the coming days.
The GORISK scientific network would like to thank A.G. Davies1, D. Pieri1 and G. Vaughan2 for their help in acquiring ASTER, Hyperion and ALI images. A special thank to Sergey Samsonov3 for the production of the first SAR interferogram of the eruption.
1- Jet Propulsion Laboratory, USA
2- U.S. Geological Survey, USA
3- Canada Center for Remote Sensing, Canada