Abstract:Nyiragongo volcano (D.R. Congo), 3,470 m a.s.l., located in the Virunga Volcanic Province (VVP) along the western branch of the East African rift, is one of the few volcanoes on Earth that several times has hosted a lava lake with decadal persistence, here inside the ∼1.2-km wide summit crater (Lev et al., 2019; Figure 1a). Flank eruptions and associated drainage of its lava lake occurred at least three times,
“…This observation was a matter of concern 27 but did not allow the forecasting of the 2021 eruption. In contrast to the the pre-2002 situation, in which the lava lake had been encrusted since 1995, the lava lake was actively convecting before the eruption, implying a steady magma and gas supply from the deep (more than 10 km) magma plumbing system 28 , which is demonstrated by our finding of deeply derived olivine crystals within the lava samples. Fig.…”
Section: Mainmentioning
confidence: 57%
“…7 ). Lava filling of Nyiragongo Crater has been ongoing intermittently since the 2002 eruption 27 , 28 . Beginning in 2020, lava started to inundate the remnant platform of the 2002 crater collapse, but was still around 85 m below the level reached before the 1977 eruption.…”
Classical mechanisms of volcanic eruptions mostly involve pressure buildup and magma ascent towards the surface1. Such processes produce geophysical and geochemical signals that may be detected and interpreted as eruption precursors1–3. On 22 May 2021, Mount Nyiragongo (Democratic Republic of the Congo), an open-vent volcano with a persistent lava lake perched within its summit crater, shook up this interpretation by producing an approximately six-hour-long flank eruption without apparent precursors, followed—rather than preceded—by lateral magma motion into the crust. Here we show that this reversed sequence was most likely initiated by a rupture of the edifice, producing deadly lava flows and triggering a voluminous 25-km-long dyke intrusion. The dyke propagated southwards at very shallow depth (less than 500 m) underneath the cities of Goma (Democratic Republic of the Congo) and Gisenyi (Rwanda), as well as Lake Kivu. This volcanic crisis raises new questions about the mechanisms controlling such eruptions and the possibility of facing substantially more hazardous events, such as effusions within densely urbanized areas, phreato-magmatism or a limnic eruption from the gas-rich Lake Kivu. It also more generally highlights the challenges faced with open-vent volcanoes for monitoring, early detection and risk management when a significant volume of magma is stored close to the surface.
“…This observation was a matter of concern 27 but did not allow the forecasting of the 2021 eruption. In contrast to the the pre-2002 situation, in which the lava lake had been encrusted since 1995, the lava lake was actively convecting before the eruption, implying a steady magma and gas supply from the deep (more than 10 km) magma plumbing system 28 , which is demonstrated by our finding of deeply derived olivine crystals within the lava samples. Fig.…”
Section: Mainmentioning
confidence: 57%
“…7 ). Lava filling of Nyiragongo Crater has been ongoing intermittently since the 2002 eruption 27 , 28 . Beginning in 2020, lava started to inundate the remnant platform of the 2002 crater collapse, but was still around 85 m below the level reached before the 1977 eruption.…”
Classical mechanisms of volcanic eruptions mostly involve pressure buildup and magma ascent towards the surface1. Such processes produce geophysical and geochemical signals that may be detected and interpreted as eruption precursors1–3. On 22 May 2021, Mount Nyiragongo (Democratic Republic of the Congo), an open-vent volcano with a persistent lava lake perched within its summit crater, shook up this interpretation by producing an approximately six-hour-long flank eruption without apparent precursors, followed—rather than preceded—by lateral magma motion into the crust. Here we show that this reversed sequence was most likely initiated by a rupture of the edifice, producing deadly lava flows and triggering a voluminous 25-km-long dyke intrusion. The dyke propagated southwards at very shallow depth (less than 500 m) underneath the cities of Goma (Democratic Republic of the Congo) and Gisenyi (Rwanda), as well as Lake Kivu. This volcanic crisis raises new questions about the mechanisms controlling such eruptions and the possibility of facing substantially more hazardous events, such as effusions within densely urbanized areas, phreato-magmatism or a limnic eruption from the gas-rich Lake Kivu. It also more generally highlights the challenges faced with open-vent volcanoes for monitoring, early detection and risk management when a significant volume of magma is stored close to the surface.
“…Over the past century, Nyiragongo hosted the largest long-lived lava lake on Earth (Lev et al, 2019) and its eruptive activity occurred mainly within the crater (Barrière et al, 2022). Prior to the 2021 eruption, only two historical flank eruptions were recordedin 1977 (Tazieff, 1977) and 2002 (Komorowski et al, 2002;Wauthier et al, 2012).…”
“…At explosive volcanoes, this mainly consists of dome growth measurements, to anticipate explosions and pyroclastic flows (e.g., Pallister et al, 2013). At some effusive volcanoes with lava lake activity, SAR shadows have been used to measure lava lake height within Nyiragongo crater (SAsha method) (Barrière et al, 2018(Barrière et al, , 2022 or at Erta Ale (Moore et al, 2019).…”
Section: Introduction 1sar Amplitude Imagery For Volcano Monitoringmentioning
Crater morphology at active volcanoes can change rapidly. Quantifying
changes during the course of a volcanic unrest episode may help assess
the level of volcanic activity. However, limitations such as crater
accessibility, cloud cover or intra-crater eruptive activity may hamper
regular optical or on-site crater monitoring. Here we use multi-sensor
satellite Synthetic Aperture Radar (SAR) imagery to produce dense time
series of quantitative indicators of crater morphological changes. High
temporal resolution is achieved by combining images from a variety of
sensors and acquisition modes, though the diversity of acquisition
geometries (incidence angle, viewing direction, resolution…)
prevents direct comparison between the different images. Using basic
trigonometry assumptions, we develop PickCraterSAR, an open-access tool
written in Python to measure crater radius and depth from SAR amplitude
images in radar geometry. We apply our methodology to study the crater
collapse associated with the May 2021 and January 2002 eruptions of
Nyiragongo volcano. After the 2021 collapse, we estimate the maximum
depth of the crater to be 850 m below the rim and the total volume to be
84$\pm$10 Mm$^3$ (270 m deeper but only 15-20
\% more voluminous than the post-2002 eruption crater).
We also show that the 2021 crater collapse occurred progressively while
a dike intrusion was migrating toward the south.
“…Nyiragongo is an active volcano in the DR Congo, and one of the eight major volcanoes of the Virunga Volcanic Province (VVP) located in the western branch of the East African Rift system, generally characterized by the presence of a persistent lava lake in its summit crater (Tazieff, 1949(Tazieff, , 1984Durieux, 2002;Barrière et al, 2022). Nyiragongo is among the most active volcanoes on Earth (Wright et al, 2015) and threatens the city of Goma, which was impacted by flank eruptions in 1977, 2002, and 2021, which drained the lava lake system at that time (e.g., Pottier, 1978;Komorowski et al, 2002;Barrière et al, 2022). The lava field of Nyiragongo is also characterised by numerous parasitic cones mostly located at the foot of the main edifice or along radial fracture zones, some of which erupted explosively (Poppe et al, 2016).…”
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