Marsili undersea volcano - tsunami risk for Naples, and coastal areas of South West italy and northern Sicily

Marsili is a large undersea volcano in the Tyrrhenian Sea, about 175 km south of Naples. The seamount is about 3,000 m (9,800 feet) tall; its peak and crater are about 450 m below the sea surface. Though it has not erupted in recorded history, volcanologists believe that Marsili is a relatively fragile-walled structure, made of low-density and unstable rocks, fed by the underlying shallow magma chamber. Volcanologists with the Italian National Institute of Geophysics and Volcanology (INGV) announced on March 29, 2010 that steep flanks of the Marsili seamount might experience an undersea landslide that could trigger destructive tsunamis on the Italian coast. They came to this conclusion after studying the collapse of 50 cubic kiloemters of material from the Vavilov Seamount which seems to have taken place in a single event. Marsili's steep flank contains around 100 km3 of weak rock.

A 2018 analysis by Alberico et al for the Naples region estimated the size of tsunami that could be generated and found that there is a risk of

"a tsunami amplitude varying from a few centimetres (30–40 cm) to some metres (1–4 m)"

It would take 20 - 25 minutes to get to the coast so another study by Nicola et al recommends

"the installation of an alert system need along the tyrrhenian coast of Calabria, with an alert advise of around 10 minutes and an evacuation plan of 10 minutes."

Geomorphology
Mt. Marsili belongs to the Aeolian Islands Volcanic arc, being 70 kilometers long and 30 kilometer wide (covering a 2100 square km area) it is the largest active volcano of the chain, larger than Mount Etna. It was discovered during the 1920s and named after Italian geologist Luigi Ferdinando Marsili. Extensive studies have been carried on only since 2005 as the Italian National Research Council started a vulcanology research program on the site.

The volcano rises from a plateau of thin oceanic (or pseudo-oceanic) crust with a thickness of only 10 km, which forms its own sea basin. The basin crust is made of tholeiitic basalt which is most typical of inflated basins at the back of oceanic volcanic arcs. The Marsili basin appears to have formed very recently (2 million years) as a consequence of the growth of the volcanic arc, and Mt. Marsili could be the result of the thermal inflation of the thin crust at the center of the basin. The start of the volcano activity could date back as recently as 200,000 years ago. Evidence of magma flows on the mountain flanks were found. Evidence of catastrophic collapses of previous other undersea volcanoes in the same area was also found.