91444 - Volcanic stratigraphy

Learning outcomes

At the end of the course, the student has acquired skills on the study of volcanic deposits and morphologies and their stratigraphy to allow the reconstruction of the internal structure of volcanic edifices and to interpret the main eruptive and post-eruptive processes, as essential inputs for volcanological analysis and modeling, hazard and volcanic risk assessments, geo-resources and territorial and geo-cultural planning. In particular, the student is able to: • interpret the volcanic deposits (volcanoclastic and lavas) in relation to the eruptive processes that determined their formation • define the main eruptive parameters useful for evaluating the volcanic hazard in terms of physical volcanology • recognize volcanic morphologies and volcano-tectonic collapse based on the interaction between tectonics and eruptive activity • identify the discontinuity surfaces that characterize the volcanic successions and use them as fundamental tools for correlation and stratigraphic classification • define the temporal development of the eruptive activity in recent and / or ancient volcanoes and the recurrence of eruptions for the purpose of assessing the volcanic hazard and risk • know the main stratigraphic, petrological and geophysical techniques necessary for the reconstruction of the internal structure of volcanoes and their potential in terms of geo-resources.

Course contents

the course is organized into different sections aimed at providing the tools necessary for the study of the stratigraphy and structure of a volcano in order to define its eruptive history and the recurrence of events, the main eruptive processes and the corresponding volcanic and collapse morphologies, and the eruptive parameters obtained from the quantification of geological characteristics of volcanic deposits, with particular reference to cartography techniques in volcanic areas as a basic tool for volcanic hazard assessments, resource supply and land planning. I – General characteristics of volcanism. Physico-chemical properties of magmas. Magma fragmentation mechanisms. II - Principles of fieldwork and stratigraphy of volcanic areas. Lithostratigraphic units and lithofacies, and Unconformity-bounded Units. III – Volcano-tectonics. Use of the morphological factor to define the eruptive centers and the relationships between local and regional volcanic and tectonic activity. Identification of dikes and volcanic conduits. Recognition of volcanic collapse structures (calderas and sector collapses) and the feedback mechanisms between collapses and volcanic activity. IV – Characterization of the eruptive processes. a) Effusive Volcanism. Characteristics and flow dynamics of mafic lava flows (pahoehoe and aa); definition of the maximum distance travelled. Characteristics and flow dynamics of silicic lavas (blocky lava flows, coulees, volcanic domes); dynamics of fracturing and secondary explosive activity. b) Explosive volcanism. Eruptive column and fall deposits; definition of the map of the isopachs and quantification of the volume (DRE) of an eruption; definition of the isopleth map; quantification of the height of the eruptive column and the intensity of an eruption; definition of the critical mass loading of a fall deposit. Distribution area of ballistic clasts. Density pyroclastic currents and related deposits; definition of the distribution area; quantification of temperature, velocity and density of a pyroclastic current, and estimation of the dynamic pressure on the basis of the corresponding deposits. Submarine explosive activity and stabilization of a volcanic island. c) Calderas and caldera-forming ignimbrites; subsurface structure and distribution of associated deposits. d) Sector collapses and debris avalanche; distribution area. e) Sin- and post-eruptive lahar flows; distribution area. V – Definition of the eruptive history of a volcano and of the recurrence of eruptive events. Recognition and classification of unconformities and paleosols. Methods of absolute dating of volcanic products. Tefrostratigraphy. VI – Petrological and geophysical methods for defining the structure of a volcanic edifice and locating magma chambers for the purpose of assessing volcanic hazards.

Teacher in charge: Prof. Federico Lucchi

Collaborator teacher: Dr. Matteo Roverato

The course is organized into 24 hours of frontal lessons (3 CFU), 10 hours of laboratory exercise (1 CFU) and 24 hours of field activity (2 CFU)

The course is characterized by one or more fieldtrips in italian volcanic areas aimed at putting into practice the concepts acquired during the frontal lessons

Readings/Bibliography

Power Point lecture notes.

• R.A.F. Cas, J.W. Wright, 1987. Volcanic successions: modern and ancient. London Unwin Hyman.

• H. Sigurdsson (Ed.), 2000. Encyclopedia of Volcanoes. Accademic press, San Diego, U.S.A.

• M.J. Branney, P. Kokelaar, 2002. Pyroclastic density currents and the sedimentation of ignimbrites. Geological Society of London, Memoirs 27.

• H.U. Schminke, 2004. Volcanism. Springer-Verlag, Berlin Heidelberg

Teaching methods

PowerPoint presentations.

Presentations by students with discussion of course topics or scientific publications of interest

Recognition of volcanic rocks and deposits through hand samples or outcrop photographs.

Field activity aimed at verifying the learning of the concepts treated during the room lectures.

In consideration of the types of activities and teaching methods adopted, the attendance of this course requires all students to carry out modules 1 and 2 in e-learning [https://www.unibo.it/it/servizi- e-opportunities / health-and-assistance / health-and-safety / safety-and-health-in-places-of-study-and-training] and participation in module 3 of specific training on safety and health in places of study. Information on dates and methods of attendance of module 3 can be consulted in the specific section of the degree program website.

Assessment methods

Oral exam

Field exercises of volcanic stratigraphy during the fieldtrips

Teaching tools

Video-projector

Scientific publications

Hand samples

Geological maps

Office hours

See the website of Federico Lucchi

See the website of Matteo Roverato