A new, 11th intense paroxysmal eruptive period in a row took place at the volcano yesterday.
The activity followed a usual several-hours lasting strong seismic tremor, a typical precursor of rapid magma flux towards the summit. At 17:10 local time yesterday, it culminated in constant dense ash emissions spewing tephra up to 40,000 ft (12 km) elevation to the east of the volcano. The National Weather Service reported that the ash column was accompanied by volcanic lightning, suggesting ash-rich fine emissions in the plume. So-called dirty thunderstorms form when ash that is to be erupted begins as electrostatically neutral rock fragments. Heat and motion of fragmented material within volcano edifice is among the first source of particle charging, then another fundamental phenomenon to being charged is friction. In order to create volcanic lightning, neutrally charged ash particles must come in contact with another object of differently charged qualities.
The local alert level for the volcano was raised to RED.
The local people from False Pass informed about fresh ash deposits between 18:00 and 20:30 local time.
In a couple hours later, at about 18:30 local time, the seismic activity started to wane rapidly, but remained elevated until 21:00 local time. The ash plume has been lowering its altitude to approx. 22,500 ft (6,8 km), however the volcanic lightning continued during the decreased period until 20:48 local time.
The seismic instrument detected recordings related to pre-eruptive levels, resulting in lowering the alert level back to ORANGE.
Source: Alaska Volcano Observatory volcano activity update 16 September 2023
