The relationship between eruptive activity, flank collapse, and sea level at volcanic islands: A long‐term (>1 Ma) record offshore Montserrat, Lesser Antilles

Abstract

Hole U1395B, drilled southeast of Montserrat during Integrated Ocean Drilling Program Expedition 340, provides a long (>1 Ma) and detailed record of eruptive and mass-wasting events (>130 discrete events). This record can be used to explore the temporal evolution in volcanic activity and landslides at an arc volcano. Analysis of tephra fall and volcaniclastic turbidite deposits in the drill cores reveals three heightened periods of volcanic activity on the island of Montserrat (930 to 900 ka, 810 to 760 ka, and 190 to 120 ka) that coincide with periods of increased volcano instability and mass-wasting. The youngest of these periods marks the peak in activity at the Soufriè re Hills volcano. The largest flank collapse of this volcano (130 ka) occurred toward the end of this period, and two younger landslides also occurred during a period of relatively elevated volcanism. These three landslides represent the only large (>0.3 km 3 ) flank collapses of the Soufriè re Hills edifice, and their timing also coincides with periods of rapid sea level rise (>5 m/ka). Available age data from other island arc volcanoes suggest a general correlation between the timing of large landslides and periods of rapid sea level rise, but this is not observed for volcanoes in intraplate ocean settings. We thus infer that rapid sea level rise may modulate the timing of collapse at island arc volcanoes, but not in larger ocean-island settings.

A decade of volcanic construction and destruction at the summit of NW Rota‐1 seamount: 2004–2014

“…Once a height and slope threshold of instability is reached, these edifices begin to disaggregate in the form of small‐scale creep, episodic landsliding, and major sector collapse. Our knowledge of seamount evolution has been largely based on ocean‐island volcanoes with subaerial portions and unstable flanks, such as Hawaii, the Canary Islands, and Tristan da Cunha [ Holcomb and Searle , ; Moore et al ., ; Krastel et al ., ; Mitchell et al ., ; Mitchell , ; Caratori Tontini et al ., ] and more recently on arc‐related volcanic islands such as Montserrat and other sites in the Lesser Antilles [e.g., Coussens et al ., ; Le Friant et al ., ; Watt et al ., ]. The repetitive growth and collapse of smaller, completely submarine arc volcanoes is more poorly studied.…”

“…NW Rota‐1 has been studied for only 10 years, during which time one landslide occurred. Gaps between eruptive periods at sites in the Lesser Antilles ranged from tens to hundreds of thousands of years [ Coussens et al ., ; Le Friant et al ., ]. The study of older landslides is limited in areas of high sedimentation, but large slides as old as 15 Ma have been identified off the Canary Islands [ Krastel et al ., ], suggesting gaps of hundreds of thousands of years up to millions of years between major events.…”

“…Coussens et al . [] show a link between periods of volcanic activity at Montserrat and increased volcano instability, in the form of landslides. It therefore seems likely that eruptions, perhaps with a minimum intensity threshold, are a strong triggering mechanism for slope collapse but that hydrothermal activity contributes to weakening slopes, increasing the likelihood of sector or flank collapse.…”

“…Coussens et al . [] found that mass wasting events at Montserrat were roughly associated with periods of rapid global sea level rise. This proved true for other island arc volcanoes as well, but not for intraplate volcanoes.…”

Submarine Depositional Terraces at Salina Island (Southern Tyrrhenian Sea) and Implications on the Late-Quaternary Evolution of the Insular Shelf

“…In the last few decades, recent advances in seafloor imagery systems enabled to extensively map the submarine flanks of volcanic islands in different geodynamic setting, revealing a large variability of landforms due to volcanic, tectonic, and erosive-depositional processes [1][2][3][4][5][6][7][8]. Until now, most of these studies focused on large-scale instability processes affecting volcanic flanks, mainly in relation to their associated tsunamigenic potential and geohazard assessment [9][10][11][12].…”