Volcanologist

When there are no signs of an active magma chamber beneath the volcano (no unusual seismic activity, no volcanic gasses escaping etc.), and when there hasn't been any activity for a long time span (at least 10,000 years).

Many volcanoes have been in continuous eruption for decades. Etna, Stromboli, and Yasur have been erupting for hundreds or thousands of years.

The following 4 volcanoes emit the most lava. Kilauea (Hawaii), Mt Etna (Italy), Piton de la Fournaise (Réunion), Nyamuragira, (D.R. Congo)

The size of volcanic eruptions is determined by the amount of lava emitted. The largest eruption over the past 2 centuries was Tambora in Indonesia in 1815.

Large volcanic eruptions are more frequent than asteroid impacts of similar magnitude.