# Indonesia volcanic activity late July 2026

> Live situation record from CLSTR: https://clstr.news/situations/recent-volcanic-eruptions-in-asia-prompt-aviation-disruptions-and-hazard-alerts
> Updated: 2026-08-18T15:52:06.000Z. Sources: 46. Developments: 33.

Indonesia’s principal volcanoes remained unsettled through late July 2026. After the July 18 eruptions of Gunung Semeru that sent a 1-km ash column skyward and prompted a Level III alert with a 5-km summit exclusion and a 13-km river-valley restriction, the agency kept the same safety measures in place. The same day, the Lewotobi-Laki-Laki plume prompted a Level II warning for nearby communities.

On July 21, Gunung Sorikmarapi experienced a surge of 40 deep volcanic earthquakes and several tectonic events, leading authorities to maintain a Level II alert and a 1.5-km crater exclusion zone.

Semeru erupted twice on July 23 (00:29 and 05:48 WIB). No visible plume was recorded, but monitoring stations logged 19 eruption tremors (13-22 mm) plus numerous embusan, harmonic, tectonic and rock-fall tremors. The Level III alert and exclusion zones (5 km radius, 13 km along river valleys) remained unchanged.

Mount Lewotobi Laki-laki showed renewed activity on July 25-26, erupting three times on the 25th and four more on the 26th. Ash plumes reached up to 800 m, and seismic amplitudes varied from 5.1 to 29.6 mm. Residents were advised to stay at least 5 km from the summit as ash drifted west- and southwest.

National geological agencies continue to monitor all sites closely, maintaining current alert levels and exclusion zones while assessing further eruption risk for surrounding communities.

## Timeline

### 2026-08-18: Indonesia faces multiple volcanic eruptions and forest fires

Indonesia faces multiple natural disasters as Mount Ibu, Lewotobi Laki-laki, and Semeru erupt, while forest fires in the Arjuno-Welirang region have forced the closure of all hiking trails.

10 sources. https://clstr.news/cluster/mount-semeru-erupts-with-hot-cloud-avalanches-in-east-java

### 2026-08-02: Mount Lewotobi Laki-laki erupts, ash plume 1 km high in East Flores

Mount Lewotobi Laki‑laki erupted on 2 Aug 2026, producing a 1 km ash plume; authorities issued a Level III alert and safety measures for nearby residents.

7 sources. https://clstr.news/cluster/mount-lewotobi-laki-laki-erupts-ash-plume-1-km-high-in-east-flores

### 2026-07-25: Mount Lewotobi Laki-laki erupts multiple times, ash plumes reach 800 m in Indonesia

Mount Lewotobi Laki‑laki in East Nusa Tenggara erupted three times on 25 July and four times on 26 July 2026, sending ash plumes up to 800 m and prompting a 5‑km evacuation warning.

2 sources. https://clstr.news/cluster/mount-lewotobi-laki-laki-erupts-multiple-times-ash-plumes-reach-800-m-in-indonesia

### 2026-07-23: Gunung Semeru erupts twice as tremor activity dominates

Gunung Semeru erupted twice early Thursday, with dozens of tremors recorded and alert level III maintained; residents barred from a 5 km zone around the summit.

5 sources. https://clstr.news/cluster/gunung-semeru-erupts-twice-as-tremor-activity-dominates

### 2026-07-21: Gunung Sorikmarapi Volcano Activity Rises, Authorities Issue 1.5 km Exclusion Zone

Gunung Sorikmarapi in North Sumatra saw a sharp rise in deep volcanic earthquakes on 18 July 2026, prompting a Level II warning and a 1.5 km exclusion zone around the crater.

6 sources. https://clstr.news/cluster/gunung-sorikmarapi-volcano-activity-rises-authorities-issue-15-km-exclusion-zone

### 2026-07-18: Mount Lewotobi Laki-Laki Eruption Sends 1,000‑Meter Ash Plume in Indonesia

Mount Lewotobi Laki‑Laki erupted on 18 July 2026, sending a 1,000 m ash plume, prompting a Level III alert, a 5 km evacuation zone and health warnings in Indonesia.

4 sources. https://clstr.news/cluster/mount-lewotobi-laki-laki-eruption-sends-1000meter-ash-plume-in-indonesia

### 2026-07-18: Gunung Semeru erupts in Java, sending hot clouds 3.5 km down slopes

Gunung Semeru erupted on Saturday, sending a 1,000‑m ash column and a 3.5‑km hot cloud toward Besuk Kobokan; alert Level III stays, with safety zones imposed.

2 sources. https://clstr.news/cluster/gunung-semeru-erupts-in-java-sending-hot-clouds-35-km-down-slopes

### 2026-07-14: Indonesia's Dukono and Semeru Volcanoes Erupt on July 15, 2026

Mount Dukono and Mount Semeru erupted on July 15, 2026, sending ash columns up to 2.3 km and 1.2 km high, prompting alert levels II and III and safety warnings across Indonesia.

6 sources. https://clstr.news/cluster/mount-semeru-erupts-repeatedly-ash-plume-reaches-1300-m

### 2026-07-12: Indonesia's Merapi and Semeru Volcanoes Erupt in Mid‑July 2026

Indonesia’s Merapi and Semeru volcanoes erupted on July 12‑13 2026, sending lava avalanches up to 2 km and ash plumes 800‑900 m high, prompting Level III alerts and safety zones.

5 sources. https://clstr.news/cluster/bright-greenblue-meteor-streaks-across-java-producing-loud-boom

### 2026-07-11: Anak Krakatau’s Level III Alert Prompts Banten Evacuation Plans

Indonesia raised Anak Krakatau to Level III (Siaga) after heightened volcanic activity in June, prompting Banten’s disaster agency to strengthen tsunami mitigation, issue a 40‑minute evacuation window and keep

3 sources. https://clstr.news/cluster/anak-krakataus-level-iii-alert-prompts-banten-evacuation-plans

### 2026-07-10: Mount Merapi launches hot cloud 2 km southwest, officials warn residents

Mount Merapi emitted a hot cloud that traveled 2 km southwest on 10 July 2026; BPPTKG logged a 34 mm amplitude, 137 s duration and urged residents to avoid the dangerous zone.

2 sources. https://clstr.news/cluster/mount-merapi-launches-hot-cloud-2-km-southwest-officials-warn-residents

### 2026-07-08: Anak Krakatau erupts multiple times, ash plume reaches up to 250 m

Anak Krakatau erupted five times on 8 July 2026, sending ash up to 250 m high; authorities set a 3 km safety zone and issued a Level III alert.

2 sources. https://clstr.news/cluster/anak-krakatau-erupts-multiple-times-ash-plume-reaches-up-to-250-m

### 2026-07-05: Indonesia's Lewotobi Volcano erupts, ash plume reaches up to 1,400 m

Lewotobi Volcano in Indonesia erupted on 6‑7 July 2026, sending ash plumes up to 1,400 m; authorities ordered a 5 km evacuation zone and warned of lahars.

2 sources. https://clstr.news/cluster/indonesias-lewotobi-volcano-erupts-ash-plume-reaches-up-to-1400-m

### 2026-07-05: Mount Semeru erupts 1 km, authorities warn of ash, lava flow and secondary explosions

Mount Semeru erupted on 6 July 2026, sending a 1 km ash column aloft; officials set 5‑km and 13‑km safety zones, warned sand‑miners of secondary explosions, and debunked a hoax eruption video.

6 sources. https://clstr.news/cluster/gunung-semeru-erupts-authorities-issue-safety-zones-as-hoax-video-is-debunked

### 2026-07-04: Gunung Anak Krakatau Stay on Level III Alert; Tourism Persists, Hoax Video Denied

Gunung Anak Krakatau stays at Level III alert after minor eruptions on July 2‑3; authorities say tourism on Pulau Sebesi and Anyer beaches is safe and a viral eruption video is a hoax.

6 sources. https://clstr.news/cluster/anak-krakatau-level-iii-alert-keeps-pulau-sebesi-tourism-strong-amid-hoax-eruption-video

### 2026-07-03: Mount Semeru erupts repeatedly; hiking trail closed through August for Hari Raya Karo

Mount Semeru erupted repeatedly on 3‑4 July 2026, prompting a Level III alert, activity bans near the crater, and a temporary trail closure from 7‑18 August for the Karo holiday; officials also warned against a

6 sources. https://clstr.news/cluster/gunung-semeru-erupts-multiple-times-as-trail-closes-for-karo-holiday

### 2026-07-02: Anak Krakatau raised to Level III alert after July eruption

Indonesia’s Geological Agency raised Anak Krakatau to Level III alert on July 2‑3, 2026, after a surge in volcanic earthquakes and a 200‑m ash‑column eruption, imposing a 3‑km exclusion zone for residents and游客

6 sources. https://clstr.news/cluster/mount-anak-krakatau-erupts-alert-raised-to-level-iii-with-3-km-exclusion-zone

### 2026-07-01: Gunung Merapi Climbing Remains Closed as Activity Stays at Alert Level III

Gunung Merapi remains at Alert Level III, keeping climbing routes closed; Yogyakarta’s governor urges tourists to wait, citing safety zones and BPPTKG guidance.

2 sources. https://clstr.news/cluster/gunung-merapi-climbing-remains-closed-as-activity-stays-at-alert-level-iii

### 2026-06-29: Merapi climbing routes remain closed amid ongoing volcanic alert

BTNGM confirms Merapi climbing trails stay closed as the volcano remains at Alert level, rejecting viral claims of reopening and urging reliance on official safety updates.

4 sources. https://clstr.news/cluster/merapi-climbing-routes-remain-closed-amid-ongoing-volcanic-alert

### 2026-06-28: Mount Semeru erupts, ash plume 1 km high, alert issued

On 28 June 2026, Mount Semeru in Indonesia erupted four times, sending ash up to 1 km high; officials raised the alert to Level III and warned people to avoid the crater and nearby river valleys because of ash,

4 sources. https://clstr.news/cluster/mount-semeru-erupts-ash-plume-1-km-high-alert-issued

### 2026-06-26: Indonesia's Lewotobi Laki-Laki and Ili Lewotolok volcanoes erupt

On 26 June 2026, Indonesia's Lewotobi Laki‑Laki erupted with a 1.2 km ash plume, while nearby Ili Lewotolok logged 59 eruptions, prompting Level II warnings and exclusion zones for locals and tourists.

2 sources. https://clstr.news/cluster/indonesias-lewotobi-laki-laki-and-ili-lewotolok-volcanoes-erupt

### 2026-06-21: June 2026 volcanic activity surge spans Iceland, Indonesia, Italy and Central America

June 2026 saw new unrest at Bárðarbunga, Dempo, Etna and others, plus ongoing eruptions in Guatemala, Mexico, Indonesia and elsewhere, prompting alerts but no major urban threats.

2 sources. https://clstr.news/cluster/june-2026-volcanic-activity-surge-spans-iceland-indonesia-italy-and-central-america

### 2026-06-20: Mount Semeru eruption injures sand miner, prompts evacuations in East Java

Mount Semeru erupted, sending ash 4.5 km up and pyroclastic flows that burned sand miner Very Irawan over 80% of his body; one person injured and residents evacuated in East Java.

2 sources. https://clstr.news/cluster/mount-semeru-eruption-injures-sand-miner-prompts-evacuations-in-east-java

### 2026-06-15: Indonesia's Merapi and Semeru volcanoes stay on alert

Indonesia's Merapi and Semeru volcanoes remain at alert level 3, with ongoing eruptions, ash plumes and seismic activity, but no reported damage.

2 sources. https://clstr.news/cluster/indonesias-merapi-and-semeru-volcanoes-stay-on-alert

### 2026-06-12: Indonesia's Eastern Volcanoes Erupt Simultaneously

Three Indonesian volcanoes—Mount Dukono, Ibu and Lewotobi Laki‑laki—erupted on 12 June, sending 400‑500 m ash plumes; alerts issued and nearby residents advised to stay clear.

2 sources. https://clstr.news/cluster/indonesias-eastern-volcanoes-erupt-simultaneously

### 2026-06-10: Lewotobi Laki‑Laki volcano erupts in Indonesia, ash plume reaches 1,000 m

Lewotobi Laki‑Laki volcano in Indonesia erupted on 10‑11 June 2026, sending a 1,000 m ash plume. Authorities warn people to stay 5 km away, wear masks and watch for lahars.

2 sources. https://clstr.news/cluster/lewotobi-lakilaki-volcano-erupts-in-indonesia-ash-plume-reaches-1000-m

### 2026-06-09: Indonesia's Merapi and Semeru volcanoes erupt, spewing ash and pyroclastic clouds

Mount Merapi sent a 2 km pyroclastic cloud on 9 June, while Mount Semeru produced a 1,200 m ash plume on 10 June; both eruptions prompted safety warnings for nearby residents.

3 sources. https://clstr.news/cluster/indonesias-merapi-and-semeru-volcanoes-erupt-spewing-ash-and-pyroclastic-clouds

### 2026-06-07: Authorities Urge Mask Use as Ash Fall Hits East Flores, Indonesia

PVMBG urged East Flores residents to wear masks after Gunung Lewotobi's ash eruption, warned to stay 5 km away, and cautioned about lahar flood risks.

2 sources. https://clstr.news/cluster/authorities-urge-mask-use-as-ash-fall-hits-east-flores-indonesia

### 2026-06-05: Lewotobi Laki-Laki volcano erupts, ash column reaches 2,500 m in Indonesia

Lewotobi Laki‑Laki volcano erupted on June 5, 2026, sending ash 2,500 m high; a Level III alert restricts a 5 km radius, advises masks, and warns of lahars.

3 sources. https://clstr.news/cluster/lewotobi-laki-laki-volcano-erupts-ash-column-reaches-2500-m-in-indonesia

### 2026-06-03: Mount Slamet's alert zone cut to 2 km amid continued volcanic warnings and extreme weather threats

Indonesia's Mount Slamet alert zone was cut to 2 km while the volcano stays at Level II; authorities also warn of heavy rain, high seas and flood risks in Central Java.

2 sources. https://clstr.news/cluster/gunung-slamet-safety-zone-cut-to-2-km-as-activity-stays-at-level-ii

### 2026-05-25: Gunung Semeru erupts to 1,000 m, authorities issue safety warnings in East Java

Gunung Semeru erupted on 25 May 2026, reaching a 1 km ash column; PVMBG set Alert Level III and barred activity within several kilometres due to hot clouds, lava falls and lahars.

2 sources. https://clstr.news/cluster/gunung-semeru-erupts-to-1000-m-authorities-issue-safety-warnings-in-east-java

### 2026-05-12: Indonesia raises Lewotobi Laki‑laki volcano to Level III alert

Indonesia’s PVMBG raised Lewotobi Laki‑laki volcano to Level III on 12 May, citing increased deep quakes, tremor, inflation and ashfall.

2 sources. https://clstr.news/cluster/indonesia-raises-lewotobi-lakilaki-volcano-to-level-iii-alert

### 2026-05-04: Mount Semeru erupts repeatedly, officials warn of hot ash and lahars

Mount Semeru erupted seven times, sending ash up to 1,200 m and hot clouds 2 km; safety zones imposed.

2 sources. https://clstr.news/cluster/mount-semeru-erupts-repeatedly-officials-warn-of-hot-ash-and-lahars

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Cite as: Indonesia volcanic activity late July 2026. CLSTR, https://clstr.news/situations/recent-volcanic-eruptions-in-asia-prompt-aviation-disruptions-and-hazard-alerts