Apublication in the Journal of African Earth Sciences, by scientists from Involcan (Instituto de Canarias volcanologico) and the University of La Laguna, discusses the analysis of floating volcanic fragments recovered during the first phases of the 2011-2012 submarine eruption south of El Hierro / Canary Islands.
El Hierro - "Restingolitas" floating in surface, off La Restingua - photo 07.01.2012 Involcan / Guardia Civil
Sample of eruptive material floating on 18.10.2011 off El Hierro - Courtesy of Instituto Geográfico Nacional (IGN).
These fragments, fished off the port of La Restingua, were called "restingolitas". They underwent an initial determination by the PEVOLCA in 2011 that pointed a basaltic / trachyto-rhyolitic mixed composition in a ratio 10/1, and the magma mixing at the time of the eruption.
The restingolitas were composed of white vacuolar material inside, surrounded by a thin black crust least vacuolar. The black matrix seals the surface, trapping the white, spongy material, giving the whole high buoyancy, allowing it to reach the surface and drift with the ocean current.
The separate study of both components confirms that the white material comes from recycled sediments or old volcanic rocks, following a fusion at high temperature by the basaltic magma.
Diagram of the magma-sediment interaction in the El Hierro volcano responsible for the specific training of restingolitas proposed in Carracedo & others / 2012 / GVP
The composition and details of the formation of the restingolitas reassure scientists on a lower risk of explosive eruption.
The analysis highlights a unique feature of the white part of restingolitas: its relatively high content of uranium.
It reaches 30 to 40 grams per tonne, the highest uranium value of all volcanic rocks known in the Canary Islands. The high uranium concentration in the trachyto-rhyolitic party could have its origin in the selective process of transferring trace elements via hydrothermal fluids circulating within the oceanic crust and the base of the volcanic island of El Hierro.
- Science Direct / Elsevier - Petrological and geochemical Highlights in the floating fragments of the October 2011 submarine eruption offshore El Hierro (Canary Islands): Relevance of submarine hydrothermal processes – by Jose A.Rodriguez-Losada & al. - link
- IGN / Gobierno de Espana / CSIC : Informe petrologico de la erupcion de la isla de El Hierro – 2011
- Global Volcanism Program – Hierro