how did this mountain form?
It was formed as a result of the collision of two tectonic plates, the African and the Eurasian.
Mount Vesuvius
Vesuvius was formed as a result of the collision of two tectonic plates, the African and the Eurasian. 
how many times has mount vesuvius erupted since 79 ad It has erupted many times since, and is the only volcano on the European mainland to have erupted within the last hundred years. where is it located? It located on the Gulf of Naples in Campania, Italy. when did it first erupt? AD 79 which are the cities that are living near enough to be affected by an eruption? Avellino, Salerno and Naples are some of them. how is its appearance described? It is a "humpbacked" peak, consisting of a large cone partially encircled by the steep rim of a summit caldera caused by the collapse of Mount Somma. where is the last mentioned mountain located? It is located in the Province of Naples, in the Campania region of southern Italy. the volcanic mountain mentioned in the beginning is it still regarded as an active volcano? Yes
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Mount Vesuvius [SEP] Formation
Vesuvius was formed as a result of the collision of two tectonic plates, the African and the Eurasian. The former was subducted beneath the latter, deeper into the earth. As the water-saturated sediments of the oceanic African plate were pushed to hotter depths inside the planet, the water boiled off and lowered the melting point of the upper mantle enough to partially melt the rocks. Because magma is less dense than the solid rock around it, it was pushed upward. Finding a weak spot at the Earth's surface, it broke through, thus forming the volcano. The volcano is one of several which form the Campanian volcanic arc.