The weathering and element fluxes from active volcanoes to the oceans: a Montserrat case study

Abstract

The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles arc. The silicate weathering may have consumed 1.3% of the early CO 2 emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat are a net sink for atmospheric CO 2 due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as a source or sink for atmospheric CO 2 is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism. This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island's inhabitants.

The effects of large igneous provinces on the global carbon and sulphur cycles

“…Therefore, the full life cycle of basaltic material, from eruption/intrusion, complete erosion, and incorporation into carbonates, is a net sink of CO 2 (e.g. Jones et al, 2011). …”

Linking silicate weathering to riverine geochemistry—A case study from a mountainous tropical setting in west-central Panama

“…Rivers on the volcanic islands of the Lesser Antilles and in Costa Rica are also comparatively well studied (McDowell et al, 1992(McDowell et al, , 1995Rad et al, 2007Rad et al, , 2011Rad et al, , 2013Goldsmith et al, 2010;Gaillar det et al, 2011a, b;Jones et al, 2011;Lloret et al, 2011Lloret et al, , 2012. Riverine geochemistry at the watershed scale has been studied in Puerto Rico by McDowell and Asbury (1994), McDowell (1998), and Stallard and Murphy (2014).…”

“…Previous work on tropical montane rivers across the Lesser Antilles recognized that chemical weathering yields for rivers developed on intermediate volcanic rocks are highly variable and, in some instances, comparable to those for basaltic terrains (Louvat and Allègre, 1997;Dessert et al, 2001): 6-106 tons/km 2 /yr for Dominica (Goldsmith et al, 2010), ~70 tons/km 2 /yr for Montserrat (Jones et al, 2011), and 100-120 tons/km 2 /yr for Guadeloupe and Martinique (Gaillardet et al, 2011a). Such high chemical weathering yields have been ascribed to the young age of volcanic bedrock across the Caribbean Basin (Stallard, 1995) and the high temperature and precipitation conditions characteristic of the tropics (White et al, 1998).…”

Soils as pacemakers and limiters of global silicate weathering

“…8 Silicate weathering fluxes from volcanic lithologies, corrected for atmospheric and, where possible, for hydrothermal inputs (Gaillardet et al, 2011). Data are from multiple sources (Dessert et al, 2001;Dessert et al, 2009;Gaillardet et al, 2011;Goldsmith et al, 2010;Goldsmith et al, 2008;Hartmann and Moosdorf, 2011;Jones et al, 2010;Louvat and Allegre, 1998;Louvat et al, 2008;Lyons et al, 2005;Pokrovsky et al, 2005;Schopka et al, 2011). 9 Same as (7) but omitting the 79 samples from the Philippines that were heavily weighted in the volcanic dataset due to their large number (Schopka et al, 2011).…”