Seismicity and volcanism; a global perspective

Earthquakes and volcanic eruptions are episodic, related phenomena, resulting from an unstable, evolving Earth. Earthquakes span at least 2 orders of magnitude of energy release (2 of Richter magnitude), and volcanic eruptions at least 3 orders of magnitude in both volume and energy. The largest known earthquakes, of magnitude about 9.5 (as in Chile in 1960), occur somewhere on Earth on average once in less than 100 years. By contrast, the largest volcanic eruptions may exceed 10,00 km³ in volume, with intervals between them averaging more than 1 million years. The largest documented eruptions have ejected some 3,000 km³ of material and occur globally on average once in 50,000 to 100,000 years. No known seismic phenomenon has a comparable return interval.