HR: 13:55h
AN: V52E-02    [PDF]
TI: Co-eruptive deformation of Nyiragongo and Nyamulagira volcanoes, Africa, from radar interferometry
AU: * Poland, M P
EM: mpoland@usgs.gov
AF: US Geological Survey, Cascades Volcano Observatory, 1300 SE Cardinal Ct., Suite 100, Vancouver, WA 98683-9589 United States
AU: Lu, Z
EM: lu@usgs.gov
AF: US Geological Survey, EROS Data Center, SAIC, Sioux Falls, SD 57198 United States
AB: Nyiragongo and Nyamulagira volcanoes are located in the western branch of the East African Rift in the Democratic Republic of Congo. On January 17, 2002, an eruption at Nyiragongo stratovolcano sent lava flows into the city of Goma (population ~500,000), 18 km south of the summit. About 13% (4.5 km$^{2}$) of the city was destroyed and several dozen people were killed. Although the extrusion of lava on the flanks ended by January 18, intermittent volcanic activity at the summit of Nyiragongo continued through 2002 and 2003. The region experienced a second major eruption of lava on July 25, 2002, from the Nyamulagira shield, 14 km northwest of Nyiragongo. Radar interferometry results derived from RADARSAT-1, ERS-1, and ERS-2 data do not indicate significant deformation in the area between early 1997 and January 14, 2002, except for subsidence of a lava flow that erupted on the north flank of Nyamulagira in 1989-1991. Interferograms spanning January 14 to February 13, 2002, show a broad pattern of fringes across the rift valley in addition to closely spaced fringes in the vicinity of Goma. After February 13, 2002, little deformation is apparent until the July-August 2002 time period, when fringes suggesting uplift characterize the summit of Nyamulagira. From August 2002 until February 2003 no noteworthy deformation is evident, despite the occurrence of several large (M $>$ 5) tectonic earthquakes. We believe that radar interferograms covering the January 2002 eruption of Nyiragongo volcano reveal a broad rifting event accompanied by shallow dike intrusion. The temporal characteristics of the displacement field indicate the event occurred in a relatively brief period of time with little precursory or post-eruptive deformation. Inflation of Nyamulagira volcano in July-August 2002 may be the result of dike intrusion from a shallow reservoir that fed the July 25, 2002, eruption. The results suggest that the eruption of Nyiragongo on January 17, 2002, may have been driven by an episodic rifting event, while the subsequent eruption of Nyamulagira occurred without accompanying tectonism. Since 1997, minor eruptive activity at Nyiragongo, including the reemergence of a lava lake, has not been associated with significant deformation.
DE: 1299 General or miscellaneous
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
DE: 8434 Magma migration
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting