IMO reported that the fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 28 April-4 May.
According to a news source, activity at the S vent of the fifth cone, which had opened on 13 April with N and S vents, intensified at around 2030 on 26 April.
Fountaining became more explosive and lava was jetted 40-50 m high.
The lava-flow rate significantly increased; lava flowed S then E and descended a valley into Meradalir.
By 29 April activity had intensified at the fifth cone where lava ejections reached 250 m high, but had ceased at the others.
By 1 May lava flows had traveled N in Meradalir and connected to the flows that had previously descended into the valley from a fissure that opened on 5 April.
IMO noted that fountaining at the vent was steady until around 0000-0100 on 2 May when it became more pulsating.
Resting periods of 1-2 minutes were punctuated by intense fountaining reaching 100-150 m high for periods of 8-12 minutes.
Gas plumes with minor amounts of ash rose 800-900 m a.s.l.
A news source noted that on 2 May lava fountains rose over 300 m, the highest to date, and were seen from Reykjavik.
Ejecta set fire to vegetation on the hill to the S of the vent, causing a smoke plume.
The Aviation Color Code remained at Orange due to the lack of ash and tephra emissions.
Sources: Icelandic Meteorological Office (IMO),Icelandic National Broadcasting Service (RUV)