A note on maar eruption energetics: current models and their application

Hydromagmatic eruptions convert thermal into
mechanical energy via the expansion of ground- and/or
surface-water. Several models address the energetics of
these eruptions based on different physical-volcanological
approaches. Here we test different models with two case
studies in the Colli Albani Volcanic District (central Italy):
the monogenetic Prata Porci and the polygenetic Albano
maars. Test results are mutually consistent, and show
cumulative mechanical energy releases on the order of
1015–1017J for single maars. The fraction of thermal energy
turned into mechanical ranges from 0.45 (as calculated from
the theoretical maximum mechanical energy), through 0.1
(calculated from country rock fragmentation, crater formation
and ballistic ejection), to 0.03 (derived from magma
fragmentation by thermohydraulic explosions). It appears
that the energy released during the most intense hydromagmatic
events may account for a dominant fraction of the
total mechanical energy released during the whole maar
eruptive histories. Finally, we consider the role of magmatic
explosive activity intervening during maar eruptions in
causing departures from predictions of the models evaluated.