Mount Semeru erupts 1 km, authorities warn of ash, lava flow and secondary explosions

On Monday, 6 July 2026, Mount Semeru in East Java erupted in the early morning, sending an ash column about 1 kilometre (≈4 676 m above sea level) into the sky. The eruption, recorded at 05:13 WIB (and again at 08:13 WIB in a separate event), reached a maximum amplitude of 22 mm and lasted over 150 seconds.

The volcano remains at Level III (Alert) and officials have imposed strict safety zones: no activity is allowed within a 5‑km radius of the crater, and the southeast sector along the Besuk Kobokan river is closed for 13 km. Residents are also prohibited from approaching riverbanks within 500 m of the river due to the risk of hot ash, lava blocks and lahars extending up to 17 km from the summit.

Local authorities have cautioned sand‑miners about the danger of secondary explosions from residual hot volcanic material, urging them not to assume deposited debris is safe.

Separately, a video purporting to show a recent Semeru eruption was verified as fabricated by the Lumajang disaster management agency, which warned the public against sharing unverified content that could cause panic.