These are 19th century paintings, when the City of Pompeii was rediscovered. Vesuvius, which is still very active and very dangerous, is often seen smoking to this day.
Vesuvius had volcanic activity on August 23, 79 A.D., which just happened to coinside with Vulcan's feast day. The famous erruption that destroyed the city (and near by communities) followed later on.
AoSHQ: Morning Report 08.23.19
Live Science: 18 High Risk Volcanoes in the United States
Fox News: Yellowstone super volcano could be catastrophic if it blows
Instapundit: Seattle and Portland are pretty close to two of those high risk volcanoes