Skip to content

Can volcanic activity and duration of repose times be modulated by the fertility of the mantle source? The case study of Methana volcano, Greece

Răzvan-Gabriel Popa1 , Olivier Bachmann1, Marcel Guillong1, Andrea Giuliani1,2

  • Affiliations: 1Institute of Geochemistry and Petrology, ETH Zürich, Switzerland; 2Earth and Planets Laboratory, Carnegie Institution for Science, Washington DC, USA 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 207

  • Programme No: 1.9.14

  • Theme 1 > Session 9

Abstract

Magmatic systems often undergo periods of frequent eruptions, followed by quiescence. In some volcanic systems, these repose times may extend to tens of thousands of years, being highly challenging for hazard forecasting. As such, a volcano can be considered extinct before eruptions restart unexpectedly. We investigate this behaviour, along with the reasons for periods of extended volcanic quiescence and of intense volcanism. This is done by combining geochemical, isotopic and a zircon geochronological dataset of over 1,250 ages for 31 eruptions generated by Methana, an active arc volcano located 60 km south of Athens (Greece). With these data, we examine the connection between volcanic activity, magma reservoir evolution and changes in the mantle source over a timescale of 700,000 years. For this particular case study, prolonged repose times are coupled to variations in mantle source fertility. The longest volcanic pause recorded at Methana (>100,000 years) is not caused by a shortage of magma recharge, but marks an intense period of magma trapping in the crust, caused by the production of superhydrous melts (>6 wt% dissolved H2O) from a fertile mantle. During ascent towards the upper crust, such volatile-rich magmas reach water saturation at around 3-4 kbar, leading to crystallization and to a decrease in ascent velocity by 2-3 orders of magnitude, with consequent trapping before they reach the surface. This mechanism can aid the growth of magma reservoirs and foster the transition from relatively small systems (like Methana or Mt. Saint Helens) to larger and more dangerous caldera-forming volcanoes.