Magma, Volcanos, Earthquakes: What is the Role of the Asthenosphere?

The asthenosphere, a section of the Earth’s mantle which is located between 80 and 200 kilometres under the world’s surface, affects the tectonic plates’ kinematics and dynamics, and therefore the generation of earthquakes and the volcanic activity. But how can this section influence the geological phenomena which happen above ground? The new research project SAKURA, co-coordinated by the University of Bologna with its Department of Physics and Astronomy “Augusto Righi”, and by the Istituto Nazionale di Geofisica e Vulcanologia (National Institute of Geophysics and Volcanology, INGV) branch in Bologna aims to answer this question.

SAKURA is a research line of the project ROSE (Reinforcement of the Observational Systems of the Earth), funded by the Fondo per la Costruzione e la Ricerca Infrastrutturale (Fund for Infrastructure Construction) of the Italan Ministry of University and Research. This interdisciplinary project, which unites ten Italian and international research groups, intends to answer fundamental questions about the functioning of the Earth and to improve our capacity to observe it, from its depths up to the ionosphere.

“Nowadays we know that asthenosphere plays a fundamental role in the geological Earth’s processes, but we still have many questions about its composition, its physical properties, its internal heat sources, and how these elements may change according to the different areas of the world”, explained Luca De Siena, professor at the Department of Physics and Astronomy “Augusto Righi” of the University of Bologna and co-coordinator of the project together with the researcher Irene Molinari of the INGV Bologna. “Through SAKURA we aim to gain a better understanding of all these aspects, and furthermore we aim to clarify the role of the asthenosphere in the heat transfer within the Earth’s mantle, in the interactions among tectonic plates, and in magma’s generation and migration”.

The project will also focus on enhancing infrastructure that provides geophysical data in the Mediterranean, with experiments planned in the Tyrrhenian and in the Adriatic Sea, including the regions of Phlegraean Fields and Ischia.

“Through SAKURA we will launch new geophysical monitoring activities in the Mediterranean”, explained Irene Molinari, researcher at INGV Bologna and co-coordinator of the project. “We will install seismic and geodetic stations in areas that have been poorly covered so far, conduct an experiment with ocean-bottom seismometers (OBS) in the Adriatic Sea, begin the construction of innovative instruments for gravity measurement, and conduct magnetotelluric surveys in the region of Campania. We will also collect new paleomagnetic data in the Mediterranean Sea and develop innovative tomographic techniques. These new data will improve our capability to observe and interpret the deep processes which feed earthquakes and volcanos”.

By uniting geology, geophysics, volcanology, physics, and mathematics, SAKURA researchers will combine the collection of the seismic and geophysical data with the study of the molten rocks which will be analysed from both petrological and geochemical perspective. Besides, the interactions among asthenosphere, lithosphere, and magma will be simulated thanks to innovative physical-numerical models.

“The main purpose is the analysis of the chemical and physical properties of asthenosphere, including its viscosity, temperature and composition”, added Luca De Siena. “By doing so, we can better understand how this section of the upper Earth’s mantle affects tectonic plates’ dynamics, and the generation of magma and earthquakes”.

The subduction processes, which cause one plate to slide beneath another, the expansion of the ocean floor, and the tectonic transformations of the plates will be studied. The information collected (data and models) will be then used to create simulations of the Earth’s mantle’s behaviours and of the deformation of the lithosphere – the hardest external layer of the Earth, which lays on the asthenosphere.

“The results of this project will help us collect data regarding some poorly sampled areas of the Mediterranean and create more accurate models of the asthenosphere’s behaviour. This will enable us to better understand both magma’s creation and movement, and the dynamics which drive seismic and volcanic processes”, continued De Siena. “This knowledge will contribute to a better management of the geological risks and to gain a more precise overview of the Earth’s evolutionary history”.