Semeru volcano, East Java – Eruption December 2020

Published: 10th December 2020

Activity of the Volcano:

Observed Semeru on the 3-5th December from an area around 10km South of the summit area. During my stay in the area the weather conditions varied between thunderstorms, foggy and cloudfree conditions.

In the days before my arrival, a few Pyroclastic flows had occured on the Southern flank of the mountain, reaching several kilometers. During my stay in the area, rock avalanches from the summit occurred frequently, ranging from a few instances to 30-40 times per miniute. Most avalances were minor and only reached tens of meters to a 100m down the flank. In between there were occurrences were rockfall went down much further, maybe to around 1-2km below the summit crater. These larger events resembeled, or even maybe could be classified as, pyrocastic flows (see example photo no.5). As the rocks gained momentum down the flank, many got crushed and became ash clouds. At night the rockfall were visible as well, as the material were still hot (Incandescent). All observed rockfall were originating from the growing dome in the summit, rocks break free of the dome. The summit of the dome also emitted a strong lava glow at times (see for example photo 6 and 11).

Semeru also erupted a few minor grey ash plumes (see for example photo 17 and 29), to heights of maybe 100-500m above the summit. White gas bursts also occurred. On the 3rd December the activity was the strongest during my stay, and there was a steady white plume being emitted from the summit crater (see photo 2 and 3) and rockfall were the most frequent. Lahar in the rivers originating from around the volcano was also observed on the 4th and 5th December.

The volcanic activity at Semeru was similar to what I osberved during a visit in 2014, however the rockfall were more frequent during this visit. It is also important to note that the dome in the summit is much larger in 2020 compared to 2014.

Important Note:

This is my personal notes, and should not be considered as official information regarding the volcano or its activity. For updated information and official statements on the volcanic activity of Krakatau Volcano, visit the Indonesian authorities website MAGMA Indonesia. and Center for Volcanology and Geological Hazard Mitigation`(PVMBG) and BMKG – Indonesian Agency for Meteorology, Climatology and Geophysics. On Twitter (@id_magma , @vulkanologi_mbg and @infoBMKG)

The restriction/danger zone for Semeru volcano was at 4km for the Southern Sector when these photos were taken. All photos taken from outside the danger zone.



Total photos in this article: 40 (Available in Jpg/Raw.). (200+ photos not published)

Photos and Videos published are available for purchase only. If you want to purchase photos or videos, please see this page



3-5th December 2020

Photo no.1. Semeru peaking out of the clouds. December is rainy season, so most of the day it is usually cloudy. (3rd December 2020)
Photo no.2. Semeru was emitting a steady white plume on the 3rd December 2020
Photo no.3. (3rd December 2020)
Photo no.4. Incandescent rockfall from the crater and strong lava glow from crater. (3rd December 2020)
Photo no.5. Rockfall activity from the crater area continued for most of the night. (3rd December 2020)
Photo no.6. (3rd December 2020)
Photo no.7. (3rd December 2020)
Photo no.8. (3rd December 2020)
Photo no.9. (3rd December 2020)
Photo no.10. (3rd December 2020)
Photo no.11. (3rd December 2020)
Photo no.12. Morning (4th December)
Photo no.13. (Rockfall during the day, 4th December
Photo no.14. (4th December)
Photo no.15. (4th December)
Photo no.16. Small ash burst from the summit (4th December)
Photo no.17. Another ash emission (4th December)
Photo no.18. (4th December)
Photo no.19. The rockfall follows a channel on the southern flank (4th December)
Photo no.20. Cloudy evening, but the lava glow from the summit of Semeru brightens the night. (4th December)
Photo no.21. (4th December)
Photo no.22. (4th December)
Photo no.23. (4th December)
Photo no.24. (4th December)
Photo no.25. (4th December)
Photo no.26. (4th December)
Photo no.27. (4th December)
Photo no.28. (5th December)
Photo no.29. (5th December)
Photo no.30. This must be one of the most majestic views on Java. Sadly, it may only be enjoyed if you own a drone, or you happen to be a bird. Tumpak Sewu waterfall and the highest volcano on Java, Semeru, 5th December.