The Volcanic Energy Census: Eruptions Against the Earth's Heat Flow

The Earth loses heat at about 47 TW. For erupted magma at 1-4 km3/yr, density 2600 kg/m3 and enthalpy 1.2-1.6 MJ/kg, volcanic heat output is 0.099-0.527 TW (central 0.288 TW), i.e. 0.21-1.12% (central 0.61%) of total heat flow. A Tambora-class eruption (150 km3 bulk, 50 km3 dense-rock equivalent) releases about 1.82e20 J, about 20 central volcanic years, about 309 seismic years, and 12.3% of one year of total terrestrial heat loss. Volcanoes are a small, episodic leak in the planetary heat budget, not its driver.