Historical volcanism in the Canary Islands; part 1: A review of precursory and eruptive activity, eruption parameter estimates, and implications for hazard assessment

Abstract

Despite decadal–millennial repose periods, volcanoes of the Canary Islands pose significant, though poorly understood hazards to local communities and infrastructure. At least 13 volcanic eruptions forming monogenetic cones and lava flows have occurred in the archipelago since 1500 CE: six on the island of La Palma (in 1585, 1646, 1677–1678, 1712, 1949 and 1971), four on Tenerife (1704–1705, 1706, 1798 and 1909), two on Lanzarote (1730–1736 and 1824) and one on the submarine flank of El Hierro (2011–2012). In this paper, we synthesize available data on these historical eruptions, focusing on their physical characteristics and chronological development, and provide new estimates of eruption parameters, such as lava flow runout, area and volume, to inform volcanic hazard assessment in the archipelago. While incomplete and imprecise, historical records indicate that precursory seismicity began days to years prior to eruption onset, consistent with the three months of well-documented unrest for the 2011–2012 eruption. Excluding the atypical 1730–1736 event, eruptions lasted from ten days to a little under five months. Initial eruptive phases usually involved the opening of multiple vents along dike-fed fissures, with Strombolian explosive activity forming monogenetic cones. Lava flow emission generally quickly followed, and later eruptive phases were typically dominated by effusive behavior. Some eruptions (1704–1705, 1824 and 1949), however, had a complex evolution punctuated by the sequential opening of distinct vents several kilometers apart. Total lengths of vent-defined fissures range from 0.2 to 14.0 km, and maximum lava flow runout is 2.7–9.4 km, extending to the coastline in 75% of eruptions. Proximal eruptive deposits cover 1.8–7.8 km2. Published estimates of subaerial eruptive volumes average between 11 and 66 × 106 m3. In comparison, a new empirical relationship based on well-constrained lava flow area and volume data at other basaltic volcanoes yields volumes of 10–76 × 106 m3 for Canary Island eruptions. The 1730–1736 Timanfaya eruption on Lanzarote represents an outlier in the context of historical Canary Island volcanism, with a duration of 2055 days, a total fissure length ≥ 14.4 km defined by at least ten main emission centers, a maximum lava flow length of 21.7 km, a lava flow field area of 146 km2 and volume of at least 2.2–3.7 km3. Historical eruptive rates are low, at 1.0–2.1 × 106 m3/year or 7.3–11.0 × 106 m3/year including the 1730–1736 eruption, in agreement with long-term volcano growth rates based on geologic data. We find no evidence for time-predictable or volume-predictable behavior of the historical eruptive sequence, which has a mean recurrence interval of 39 ± 24 years. Our analysis outlines a useful framework for forecasting the onset, development and style of future eruptions in the archipelago. Further work, particularly detailed field-based studies of eruption deposits and petrologic reconstructions of eruption run-up processes, will help refine our understanding of historical volcanism and associated hazards in the Canary Islands.