Eruptions at Dempo volcano, Sumatra, Indonesia

Indonesian Dempo volcano started erupting at 14:15 UTC on July 25, 2023. The Aviation Color Code was raised to Orange.

• This is the first eruption at the volcano since the preheatic explosion on June 1, 2022. The volcano has a history of VEI 1 and 2 eruptions since 1817.

The height of the eruptive column was observed to be 2 km (6 560 feet) above the summit or 5 173 m (16 971 feet) above sea level, drifting south and southwest. The column had a white-to-gray color with moderate to thick intensity. The eruption was recorded on a seismograph with a maximum amplitude of 35 mm and a duration of 204 seconds.¹

The second eruption took place at 08:47 UTC on July 26. This time, the height of the eruption column was not observed. It was recorded on a seismograph with a maximum amplitude of 35 mm and a duration of 552 seconds.

The public, visitors and tourists are urged not to approach and spend the night (camping) within a 1 km (0.62 radius) of Dempo and Marapi craters, and as far as 2 km (1.2 miles) to the north, bearing in mind that the crater is the center of the eruption and volcanic gases can be dangerous to life.

Dempo is a stratovolcano located in Southeast Sumatra, rising prominently above the Pasumah Plain. The volcanic complex, made primarily of andesite, consists of two main peaks: Gunung Dempo and Gunung Marapi. Both are situated near the southeast rim of a substantial, 3 km (1.8 miles) wide amphitheater, which is open to the north.²

Gunung Dempo, the older of the two craters, has its highest point slightly lower and lies at the southeast end of the summit complex. The Marapi cone, which is taller, was constructed within the original crater of Gunung Dempo.

Historically, volcanic activity has led to the creation of seven craters at or near the summit, revealing a west-northwest migration of volcanic activity over time.

The Marapi cone has a significant 750 x 1 100 m (2 460 x 3 608 feet) active crater that cuts into its northwest side. Notably, this crater contains a lake that is 400 m (1 312 feet) wide at the far northwest end.

Historical records of eruptions at Dempo date back to 1817. The eruptions have typically been characterized as small to moderate explosions, which result in localized ashfall. As such, the volcano presents an ongoing geologic and potential hazard in the region.

References:

¹ Dempo volcano updates – PVMBG – July 25 and 26, 2023

² Dempo volcano – Geological summary – GVP

Featured image credit: Dempo volcano eruption on July 25, 2023. Credit: PVMBG