Volcanic activity intensifies at Mount Merapi, Indonesia

Indonesian authorities are reporting increased activity at Mount Merapi over the past couple of days. Lava has so far flowed up to 800 m (2 624 feet) down the slope of the volcano. Authorities are preparing evacuation routes and emergency shelters as well as calculating logistical needs in anticipation of a major eruption. The Alert Level remains at 2 (of 4).

Apart from incandescent lava, the volcano was emitting booming sounds resembling thunder more frequently, prompting local residents to also increase the frequency of their independently organized patrols, The Jakarta Post reports.

"The volume and the extent of the lava flow were both relatively normal, but the volunteer team has banned all human activity within a 3 km (1.8 miles) from the crater," JP quoted Dimas Joko, a volunteer monitoring the volcano.

"The people are still calm because the lava so far has flowed only 500 m to 800 m (1 640 - 2 624 feet) down the slope. But we remain alert, in case Merapi erupts suddenly," he said January 16.

PVMBG advised people to stay away from the upper slopes of the mountain for their own safety, especially considering the lava flow.

Authorities are preparing evacuation routes and emergency shelters as well as calculating logistical needs in anticipation of a major eruption (masks, community kitchens, emergency tents and rehabilitation posts).

PVMBG reported that during November 30 - December 6, 2018 the lava dome in Merapi’s summit crater grew at a rate of 2 200 m³ (77 700 ft³) per day. By December 6, the volume of the dome, based on photos taken from the SE, was an estimated 344 000 m³ (12.1 million ft³). White emissions of variable density rose a maximum of 150 m (490 feet) above the summit.

The Alert Level remains at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone.

Thousands of people are living on the flanks of Mount Merapi, active stratovolcano regularly erupting since 1948. It is located about 28 km (17 miles) north of Yogyakarta city (population 2.4 million).

At least 353 people were killed and more than 350 000 other displaced after the volcano erupted in 2010 (VEI 4).

In November 1994, a large explosion at the volcano produced pyroclastic flows that killed 27 people. 

Geological summary

Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano.

Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2 000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. 

Subsequently, the growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Featured image: Mount Merapi lava flow on January 14, 2019. Credit: Øystein Lund Andersen, oysteinlundandersen.com (used with permission)