The earliest eruptions of the volcano occurred around one million years ago , explosive activity producing ignimbrite . The explosive eruption phase finished around 830,000 years before present , when the nature of the activity changed to a mix of pyroclastic and effusive , lava eruptions which built up the mountain and which have been dated to around 500,000 years ago . One of the explanations advanced for the Valle dei Grigi is that it is the result of the collapse of a sector of the mountain , as occurred during the 1980 eruption of Mount St. Helens and the 1792 eruption of Mount Unzen
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
Monte Vulture