Mt. Vesuvius has the same kind of magma any volcano has. The magma chamber is a 400-square-kilometer layer of molten mantle that becomes lava when it exits the top. The mount has erupted multiple times throughout history and remains dangerous today.
The magma of Mt. Vesuvius is less dense than the surrounding rock, and when it rises to the top, the explosions are gigantic. This pyroclastic flow travels in excess of 100 mph, spitting solid and molten rock and sending gases and ash miles into the atmosphere. The most powerful recorded explosion decimated the city of Pompeii in 62 AD. According to National Geographic, the magma is closer to the surface today and may result in a less destructive explosion if it happens today.