The volcanic activity of Gunung Anak Krakatau located in the Sunda Strait continues to increase. To that end, the PVMBG of the ESDM Ministry of Gelology has upgraded the status of Gunung Anak Krakatau from Waspada (Level II) to Alert (Level III), with the danger zone extended from 2 kilometers to 5 kilometers. People and tourists are prohibited from carrying out activities within a 5 kilometer radius of the crater peak of Mount Anak Krakatau. This increase in Standby status (Level III) is valid starting from 27/12/2018 at 06.00 WIB.
Based on the PVMBG data, Gunung Anak Krakatau is active again and enters the eruption phase from July 2018. The next eruption is Strombolian eruptions, which are eruptions accompanied by throwing incandescent lava and dominant incandescent lava flows to the southeast. Fluctuating ongoing eruptions.
On 22/12/2018 there was an eruption but it was recorded as a small scale, compared to the eruption in the period September-October 2018. The results of the analysis of satellite images were known as the west-southwest slope flank collapse and avalanches entered the sea. This is the possibility that triggered the tsunami.
Since 12/22/2018, a Surtseyan type eruption was observed, namely alira lava or magma which came out of direct contact with sea water. This means the volume discharge of magma released increases and the crater hole enlarges. There may be a new crater hole that is close to the sea level. Since then the eruption took place without a pause. Sounds of eruption sound are heard several times per minute.
At present the eruption activity is still ongoing, namely in the form of Strombolian eruptions accompanied by throws of incandescent lava and hot clouds. On 12/26/2018 an eruption of hot clouds and Surtseyan was observed. This hot cloud has resulted in rain of ash. Dominant winds lead to the southwest so that volcanic ash spreads southwest to the sea. The presence of several layers of wind at certain elevations leading to the east caused rain of thin volcanic ash to fall in the city of Cilegon and partly in attack at 12/26/2018 at around 17:15 WIB. This is not dangerous. Volcanic ash actually fertilizes the soil. The community anticipates using masks and goggles when moving outside when it rains ash.
Observation of Gunung Anak Krakatau during 27/12/2018 at 00.00 - 06.00 WIB, the eruption of Gunung Anak Krakatau eruption was still ongoing, continuous tremor with an amplitude of 8-32 millimeters (dominant 25 millimeters), and a banging sound was heard.
PVMBG recommends that people and tourists be prohibited from carrying out activities within a 5 km radius of the crater peak because they are dangerously affected by eruptions in the form of incandescent rocks, hot clouds and thick volcanic ash. Within the 5 km radius there are no settlements. Meanwhile the BMKG recommends that the community not carry out activities on the coast at a 500 meter radius to 1 kilometer from the coast in anticipation of a subsequent tsunami. The tsunami that was raised underwater landslides due to the eruption of Mount Anak Krakatau.
People are encouraged to remain calm and increase their awareness. Always use information from PVMBG for volcano early warning and BMKG regarding tsunami early warning as an official institution. Do not believe in misleading information whose sources cannot be accounted for.
* Sutopo Purwo Nugroho *
Head of BNPB's Data Information and Public Relations Center