Damage from lava flows: insights from the 2014–2015 eruption of Fogo, Cape Verde
Jenkins et al. Journal of Applied Volcanology
Damage from lava flows: insights from the 2014-2015 eruption of Fogo, Cape Verde
S. F. Jenkins 0 1
S. J. Day 2
B. V. E. Faria 4
J. F. B. D. Fonseca 3
0 Earth Observatory of Singapore, Nanyang Technological University , Singapore, Singapore
1 School of Earth Sciences, University of Bristol , Bristol , UK
2 Institute for Risk and Disaster Reduction, University College London , London , UK
3 CERENA, Instituto Superior Tecnico, University of Lisbon , Lisbon , Portugal
4 National Institute of Meteorology and Geophysics , São Vicente , Cape Verde
Fast-moving lava flows during the 2014-2015 eruption of Fogo volcano in Cape Verde engulfed 75% (n = 260) of buildings within three villages in the Chã das Caldeiras area, as well as 25% of cultivable agricultural land, water storage facilities and the only road into the area. The eruption had a catastrophic impact for the closeknit communities of Chã, destroying much of their property, land and livelihoods. Volcanic risk assessment typically assumes that any object - be it a building, infrastructure or agriculture - in the path of a lava flow will be completely destroyed. Vulnerability or fragility functions for areas impacted by lava flows are thus binary: no damage in the absence of lava and complete destruction in the presence of lava. A pre-eruption field assessment of the vulnerability of buildings, infrastructure and agriculture on Fogo to the range of volcanic hazards was carried out in 2010. Many of the areas assessed were subsequently impacted by the 2014-2015 eruption and, shortly after the eruption ended, we carried out a post-eruption field assessment of the damage caused by the lava flows. In this paper, we present our findings from the damage assessment in the context of building and infrastructural vulnerability to lava flows. We found that a binary vulnerability function for lava flow impact was appropriate for most combinations of lava flow hazard and asset characteristics but that building and infrastructure type, and the flow thickness, affected the level of impact. Drawing on these observations, we have considered potential strategies for reducing physical vulnerability to lava flow impact, with a focus on buildings housing critical infrastructure. Damage assessments for lava flows are rare, and the findings and analysis presented here are important for understanding future hazard and reconstruction on Fogo and elsewhere.
Fogo; Cape Verde; Lava flows; Building; infrastructural and agricultural damage; eruption impact assessment; hazard and risk assessment; mitigation
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Introduction
Lava flows are Earth’s most common volcanic feature
and one of the most easily-recognised products of a
volcanic eruption (Kilburn 2015). They can be
categorised into three main types, according to their surface
features: pāhoehoe, ‘aʻā and blocky and all three may
occur within the same eruption. Blocky flows are
associated with more viscous lava and can be tens of metres
thick, while pāhoehoe and ʻaʻā can be produced by
chemically identical mafic lavas moving at different velocities
(faster in the case of ‘aʻā, at least initially). These types of
flow are more commonly 2–10 m thick, although pāhoehoe
flows can be thinner, particularly on initial emplacement
(Kilburn 2015). Their subsequent thickening, or inflation,
due to continued movement of magma into the interior of
the flow is common, but varies from case to case according
to the history of magma input to the flow (Calvari and
Pinkerton 1998; Walker 2009). During relatively high
effusion rate eruptions, sheet flows can also form where
fluid lava ponds in low-lying areas or where individual lobes
of lava coalesce, or at lava flow breakouts where local
effusion rates are transiently elevated (Kilburn 2015). The area
impacted by a lava flow depends upon a number of factors
including the vent location and local topography, and the
effusion rate and duration.
Descriptions of past lava flow impacts are limited and
relatively few studies (e.g. Behncke et al. 2005; Felpeto
et al. 2001; Rhodes et al. 2013) have directly assessed the
future threat of lava flows to buildings, infrastructure or
agriculture. For an overview of the historical impacts of
© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
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lava flows see Blong (1984) and the updated review of
Harris (2015). Over the past decades there have been a
number of lava flow impacts in populated areas (Table 1).
The largest lava flow impact of recent times took place
during the 2002 eruption of Nyiragongo, Democratic
Republic of Congo, in which lava flo (...truncated)