Forecasting Effusive Dynamics and Decompression Rates by Magmastatic Model at Open-vent Volcanoes.

Effusive eruptions at open-conduit volcanoes are interpreted as reactions to a disequilibrium induced by the increase in magma supply. By comparing four of the most recent effusive eruptions at Stromboli volcano (Italy), we show how the volumes of lava discharged during each eruption are linearly correlated to the topographic positions of the effusive vents. This correlation cannot be explained by an excess of pressure within a deep magma chamber and raises questions about the actual contributions of deep magma dynamics. We derive a general model based on the discharge of a shallow reservoir and the magmastatic crustal load above the vent, to explain the linear link. In addition, we show how the drastic transition from effusive to violent explosions can be related to different decompression rates. We suggest that a gravity-driven model can shed light on similar cases of lateral effusive eruptions in other volcanic systems and can provide evidence of the roles of slow decompression rates in triggering violent paroxysmal explosive eruptions, which occasionally punctuate the effusive phases at basaltic volcanoes.

Volcano seismicity and ground deformation unveil the gravity-driven magma discharge dynamics of a volcanic eruption.

Effusive eruptions are explained as the mechanism by which volcanoes restore the equilibrium perturbed by magma rising in a chamber deep in the crust. Seismic, ground deformation and topographic measurements are compared with effusion rate during the 2007 Stromboli eruption, drawing an eruptive scenario that shifts our attention from the interior of the crust to the surface. The eruption is modelled as a gravity-driven drainage of magma stored in the volcanic edifice with a minor contribution of magma supplied at a steady rate from a deep reservoir. Here we show that the discharge rate can be predicted by the contraction of the volcano edifice and that the very-long-period seismicity migrates downwards, tracking the residual volume of magma in the shallow reservoir. Gravity-driven magma discharge dynamics explain the initially high discharge rates observed during eruptive crises and greatly influence our ability to predict the evolution of effusive eruptions.

Sublingual epidermoid cyst.

Dermoid and epidermoid cysts are developmental pathologies that occur in the head and neck with an incidence ranging from 1.6 to 6.9%, and they represent less than 0.01% of all oral cavity cysts. Our purpose is to report a case of sublingual epidermoid cyst of the floor of the mouth. We studied and operated on an 18-year-old white male patient showing a large swelling of oral floor. His main symptoms were difficulty breathing, swallowing, and speaking. At his birth the patient's tongue was adherent to the floor of the mouth. His father had the same problem at birth. Both father and son underwent surgical separation of tongue, during the post-neonatal period. After the surgical removal of the swelling, under general anesthesia, all the patient's symptoms were missed. Histological examination of the mass confirmed the diagnosis of an epidermoid cyst. No relapse of the lesion was present in ten months of follow-up. Many theories are proposed on the etiology of the epidermoid and dermoid cyst. In this case a traumatic event can be found, such as an operation of the tongue in neonatal age. However a multifactorial origin must be assumed for justifying the fact that the patient's father did not develop a dermoid cyst although he had the same problem of an adherent tongue and was operated on.