Hunga Tonga-Hunga Ha'apai volcano (Tonga): major eruption sent ash up to 17 km, 86 000 lightnings in plume

After almost two weeks calm period, the activity has picked up again with a high phreatomagmatic eruptive phase.
A spectacular explosion occurred at 15:14 UTC yesterday characterized by dark and dense masses of pyroclastic material and ground-hugging currents known as base surges, typical signs of surtseyan and phreatomagmatic eruptions. An increasingly larger and dense plume sent ash up to 55,000 ft (17,000 m) altitude. Note gravity waves rippling across umbrella region in the plume as can be seen in the satellite animation.
According to available sources, 86 000 volcanic lightnings were detected in the eruption column. Such volcanic "thunderstorms" are often seen during explosive eruptions producing large quantities of ash, although the details are still poorly understood. In a simplified model, the lightnings are the result of electric charges accumulating in different parts of the eruption cloud, where friction between the ash grains rip of electric charges (electrons) from each other. The more quantity of ash emitted, the faster and more turbulent it is moving and the finer the ash grains, the more likely this process occurs.
TROPOMI satellite-based measurements of SO2 concentrations in the atmosphere show the impressive SO2 emissions ejected by the volcano amounted about 50 kilotons.

Gravity waves rippling across umbrella region in the plume during the eruption (source: GOES-17)

Ricordate la spettacolare eruzione in corso sulle isole disabitate di Hunga Tonga-Hunga Ha'Apai? E bene, dopo una settimana di relativa calma, oggi è iniziata una fase fortemente esplosiva, la più intensa dall'inizio dell'eruzione!pic.twitter.com/04vlVF1Nb2

— Il Mondo dei Terremoti (@mondoterremoti) January 13, 2022

Video of the eruption seen from boat (source: @mondoterremoti/twitter)

Ecco le prime spettacolari immagini della nuova fase esplosiva iniziata nel corso della giornata di ieri sulle isole Hunga Tonga-Hunga Ha'Apai, nella zona meridionale dell'oceano Pacifico. Ancora una volta questo tipo di attività è causata dall'interazione tra il magma e l'acqua. pic.twitter.com/06kCsnqazZ

— Il Mondo dei Terremoti (@mondoterremoti) January 14, 2022