Modeling long‐term ground deformation due to the cooling of a magma chamber: Case of Basiluzzo island, Aeolian Islands, Italy

Abstract

[1] We estimate the long-term vertical deformation of Basiluzzo island, located in the volcanic arc of the Aeolian Islands, Italy, by inferring the subsidence of a Roman age submerged wharf dated 2000 ± 50 years ago. We model the crustal deformation that produced this displacement as a cooling magma chamber emplaced during the formation of the island. This is the first attempt to model crustal deformation using the subsidence of a submerged archaeological structure. Nowadays the top of the wharf, which can be considered an unconventional leveling benchmark, is located near Punta Levante, at an average depth of 3.20 ± 0.10 m below actual sea level, and it is still in good conservation. Its present location is due to combined effect of sea level rise and volcanic and tectonic activity that occurred since it was built. Taking into account the architectural features of the wharf and that the mean sea level rise of the Mediterranean sea has been estimated as $0.45 m during the last 2000 years [Flemming and Webb, 1986], we estimate a total subsidence of 3.75 ± 0.10 m, at a rate of about 1.87 mm yr À1 [Anzidei et al., 2002]. We propose a possible mechanism for the long-term subsidence, which occurred on a timescale of thousands of years, by considering the Earth's crust as a Maxwell body. We assume that the magmatic source is located directly beneath Basiluzzo dome and underwent progressive solidification and subsequent volume reduction since its emplacement 50,000 years ago.INDEX TERMS: 8429 Volcanology: Lava rheology and morphology; 8439 Volcanology: Physics and chemistry of magma bodies; 8499 Volcanology: General or miscellaneous; KEYWORDS: volcanism, magma chamber, archaeology Citation: Tallarico, A., M. Dragoni, M. Anzidei, and A. Esposito, Modeling long-term ground deformation due to the cooling of a magma chamber: Case of

Late Quaternary deformation history of the volcanic edifice of Panarea, Aeolian Arc, Italy

“…On the short-term, subsidence at a rate of about 1.35 m/ ka over the last 2,000 years is documented at Basiluzzo. That process, which has already been corrected for the glacio-hydro-isostatic and eustatic components, was recently interpreted as the result of volcano-related crustal deformation connected with the cooling of the magma chamber corresponding to the dome of Basiluzzo (Tallarico et al 2003). On the other hand, we believe that the submergence trend at Basiluzzo could be more likely explained as the result of localized neo-tectonic displacement along main NE-SW-oriented tectonic structures in the submarine area between Panarea and Basiluzzo (Fig.…”

What causes subsidence following the 2011 eruption at Nabro (Eritrea)?

“…Observations of long-lived subsidence of the ground surface have been attributed to cooling and crystallising (hence contracting) magma at numerous volcanoes across the world, such as Medicine Lake Volcano, California (Poland et al 2006); Okmok, Aleutians (Caricchi et al 2014); Askja, Iceland; Basiluzzo island; Aeolian Islands (Tallarico et al 2003); and Volcan Alcedo, Galapagos (Hooper et al 2007). The subsidence measured in these studies is thought to have persisted for years to centuries, although the geodetic record typically only captures the most recent subsidence.…”

“…The model requires an open system as volatiles produced by crystallisation (which could theoretically re-pressurise the chamber) are not accounted for and therefore are effectively outgassed. Tallarico et al (2003) derive an expression for the volume of contraction ( V (t)) after time t since the beginning of cooling:…”

“…The subsidence measured in these studies is thought to have persisted for years to centuries, although the geodetic record typically only captures the most recent subsidence. Tallarico et al (2003) proposed a simplified first order model of the volume change induced by a cooling spherical magma chamber. The model accounts for internal magma chamber processes, such as thermal convection and its interaction with crystallisation and chemical differentiation, by allowing the radius of the chamber to change over time.…”

“…The temperature decrease induces the growth of crystals and contraction of the magma body (for full technical details, see Tallarico et al (2003)). …”