A càrrec del Dr. Olgeir Sigmarsson (CNRS, Clermont-Ferrand, France)
SEMINARIS DE LA FACULTAT DE GEOLOGIA I L'INSTITUT DE CIÈNCIES DE LA TERRA JAUME ALMERA

Universitat de Barcelona (UB)
Consell Superior d'Investigacions Científiques (CSIC)

Dia: dimarts 28 d'octubre
Hora: 12.00 h
Lloc: sala d'actes de l'Institut Jaume Almera

Resum: Explosive eruptions produce tephra that mantle landscape in the vicinity of the active volcano according to the wind direction. From the subglacial volcano, Katla in S-Iceland, we have collected over 200 tephra layers from soil sections approximately 20 km to the East of the volcano. These layers represent the volcanic activity of Katla during the last 8400 years. Major-element composition of these tephra changes significantly, most likely reflecting different configuration of the magma plumbing system beneath Katla. The plumbing system is likely to change with time from a deep-rooted dyke through a complex of dykes and sills forming a simple magma chamber. The duration of these three phases are variable but the magma chamber appears to be destroyed by exceptionally large basaltic fissure eruptions that start a new cycle of plumbing system evolution.