Recent Activity of Nyiragongo (Democratic Republic of Congo): New Insights From Field Observations and Numerical Modeling

Abstract

Nyiragongo volcano is known for its active lava lake and for socioeconomic issues arising from future possible eruptive events having major impacts on the community living in the Virunga region. The 2020 field expedition inside the summit crater has allowed the collection of unprecedented field observations to state on the current activity. Since the February 2016 intracrater event, the crater floor level has been rising much faster than during the 2010–2016 period. The current activity is reminiscent of the 1970–1972 and 1994–1995 periods preceding the lava lake drainage events in 1977 and 2002. Numerical simulations, successfully validated with data over the past 30 years, show that the rising of the crater floor could slow down in the next months/years and reach a critical equilibrium. Based on the past eruptive history and on the current activity, a flank eruption in the March 2024 to November 2027 interval could be a possible scenario.

Intra‐Crater Eruption Dynamics at Nyiragongo (D.R. Congo), 2002–2021

“…(platform 2 , see Figure 1) but there are still large uncertainties about its depth after the crater collapsed 5 days later on January 22 (Durieux, 2002) That depth allows estimating extruded volumes of lava within the crater since the 2002 eruption (see Section 3.3). This new measurement, confirmed by two independent observations, also answers to a long-standing debate that was at the origin of large and recurrent discrepancies found in the literature, for example, Durieux (2002), Tedesco et al (2007), followed by Burgi et al (2014Burgi et al ( , 2018Burgi et al ( , 2020 and relayed in a recent review article of Pouclet and Bram (2021). Presumably based on visual inspection, no information about the measurement methods nor uncertainty are given in the above-mentioned studies.…”

“…In line with extruded volumes as predicted by their model (see Figure 5c), Burgi et al (2018) suggested a ∼10 km 3 spheroidal shallow reservoir (6 km long and 0.6 km high) beneath the volcano, and mentioned an intruded volume of 0.9 km 3 in 2018. Burgi et al (2020) forecast (before the occurrence of the May 2021 eruption) a 2 km 3 intruded volume in 2025.…”

“…Based on field observations in February 2020, Burgi et al. (2020) estimated a cone height of about 45–50 m and a slope of 7° for a lava tunnel of about 180‐m length between the base of the cone and the eastern side of the lake rim ($$\mathit{L}\mathit{R}$$; see also Figure 5a for visualizing the lake‐cone distance). This implies a differential height of about 20–25 m between the lava extrusion point at the base of the cone and the lava lake's rim.…”

“…Estimates from Burgi et al. (2014, 2020) are plotted with yellow inverted triangles and a black round marker (note that four of the six points from 2006 to 2010 have a coarse monthly temporal resolution, see also Text S3 in Supporting Information S1).…”

“…Based on sparse lava-lake elevation measurements (20 data points in ∼18 years, see Figure 5c), the simulations proposed by Burgi et al (2014Burgi et al ( , 2018Burgi et al ( , 2020 are the first attempts for estimating intruded volumes after assuming a simplified geometry, that is, a vertical cylindrical conduit (4 km long, diameter of 15 m) linking a conical lava lake to a shallow magma chamber. They explained the continuous surface activity at Nyiragongo from the convective magma movement controlled by density and viscosity differences between the gas-rich ascending magma and the descending cooled and degassed magma (e.g., Stevenson & Blake, 1998).…”