Outdoor science experiments, hands-on learning in nature: the Nirano Mud Volcano (NMV, Fiorano Modenese, Italy) open-field laboratory

Mud volcanoes (MVs) are part of the “sedimentary volcanism” due to their morphological resemblance to igneous volcanoes and are characterized by the uplift of sediments and fluids (Martinelli & Judd, 2004; Mazzini & Etiope, 2017). They are widely diffused and, although not always as fascinating as “ordinary” volcanoes, no less investigated by various disciplines, e.g. botanics, microbiology, geophysics, geomorphology, geochemistry and structural geology. In particular, they are taken into account for hydrocarbon prospection, mainly gas, since they are mostly located in petroliferous basins and constitute the second natural source of CH4 (Sciarra et al., 2019) and as earthquake precursors (Martinelli & Judd, 2004). In Italy, MVs occur in both Northern and Central Apennine and in Sicily (Martinelli & Judd, 2004; Sciarra et al., 2019). Nirano mud volcano (NMV) of the Emilia Romagna region is one of the biggest in Italy, situated close to a small anticline in the outcrop of the Plio-Pleistocene “Argille Azzurre” clays (Martinelli & Judd, 2004), and is widely investigated for the gas composition (Mazzini & Etiope, 2017). Thousands of people of all ages and levels of education visit this magnificent area every year. Master geology students from the University of Ferrara, the course “geochemical prospecting”, have been putting into practice the theoretical geochemical skills of measuring in-situ temperature, pH, and electrical conductivity, as well as collecting water and mud samples for analyses (X-Ray Fluorescence, XRF; Inductively Coupled Plasma Mass Spectrometry, ICP-MS; Ion Chromatography, IC; Elemental Analyzer for coupling to Isotope Ratio Mass Spectrometers, EA-IRMS) in the laboratory. The results of their curiosity and abilities focused on the geochemical composition of NMV mud and water, as shown during the second Italian Geochemistry Society congress. The aim of this work is also to raise and increase awareness of peculiar geochemical threats in the national territory at many levels using the NMV area as an open-field laboratory, which is suitable for everyone interested in improving their geological knowledge and understanding and the processes occurring in the Earth crust (fault formation, fluid circulation, and earthquake indicators). In particular, this outdoor experience fits very well with exploring teens, who can make first-hand observations, mud, water and gas sampling (be prepared to get hands dirty!) and experience simple analyses on the field, such as pH, EC, and water salinity measurement throughout specific probes. Martinelli G. & Judd A. (2004) - Mud volcanoes of Italy. Geol. J., 39, 49-61, https://doi.org/10.1002/gj.943. Mazzini A. & Etiope G. (2017) - Mud volcanism: An updated review. Earth-Sci. Rev., 168, 81-112, https://doi. org/10.1016/j.earscirev.2017.03.001. Sciarra A. et al. (2019) - Geochemical characterization of the Nirano mud volcano, Italy. Appl. Geochem., 102, 77-87, https://doi.org/10.1016/j.apgeochem.2019.01.006.