Why do some volcanoes explode and others not?

Volcanoes erupt differently based on tectonic settings, magma properties, and whether water interacts with the magma. Divergent plate boundaries and hotspots often produce non-explosive lava flows, while convergent boundaries and phreatomagmatic interactions—where magma meets external water—tend to trigger explosive blasts.

What we know

• Volcanoes resulting from divergent tectonic activity are usually non-explosive, whereas those resulting from convergent tectonic activity cause violent eruptions. [4]
• Phreatomagmatic eruptions result from an interaction between magma and water, differing from exclusively magmatic or phreatic eruptions. [2]
• Unlike phreatic eruptions, the products of phreatomagmatic eruptions contain juvenile magmatic clasts. [2]
• Ol Doinyo Lengai uniquely erupts natrocarbonatite, an unusually low-temperature and highly fluid type of magma. [5]

Where to go next

• how it workedHow does water cause violent volcanic explosions?
• what caused itWhy do convergent tectonic boundaries cause violent eruptions?
• a case in pointWhat happened during the 2022 eruption of Mauna Loa?
• what followedHow do volcanoes affect atmospheric temperature and climate?
• compared withWhat makes Ol Doinyo Lengai's lava so unusual?
• an unexpected connectionHow can a volcano erupt at temperatures low enough to be fluid without typical silicate rock?While most volcanoes rely on extremely hot silicate magma to drive activity, Ol Doinyo Lengai breaks expectations by erupting uniquely cool and fluid natrocarbonatite.

Sources

• [1]phreatomagmatic eruption (Wikidata Q1639789) · CC0 1.0
• [2]Phreatomagmatic eruption · CC BY-SA 4.0
• [3]2022 eruption of Mauna Loa · CC BY-SA 4.0
• [4]Volcano · CC BY-SA 4.0
• [5]Ol Doinyo Lengai · CC BY-SA 4.0