The Times Australia
The Times World News

.

Mount Semeru's deadly eruption was triggered by rain and storms, making it much harder to predict

  • Written by Heather Handley, Adjunct Associate Professor, Monash University
Mount Semeru's deadly eruption was triggered by rain and storms, making it much harder to predict

The eruption of Mount Semeru in Indonesia on Saturday tragically claimed the lives of 22 people[1], with another 22 still missing and 56 injured. More than 5,000 people[2] have been affected by the eruption, and more than 2,000 people have taken refuge at 19 evacuation points.

Saturday’s eruption produced an ash plume that reached 15km into the atmosphere, along with hot pyroclastic flows[3] – dense, fast-moving clouds of solidified lava, ash and gas. Volcanic mudflows called lahars[4] also tumbled down the volcano’s steep slopes. Heavy ash blanketed nearby villages and plunged some areas into temporary darkness.

Several villages have been buried in up to 4 metres of volcanic material and debris, more than 3,000 buildings have been damaged, and Gladak Perak Bridge, which connected Lumajang with the nearby city of Malang, has collapsed.

The Volcano Observatory Notice for Aviation (VONA) has since reported[5] further pyroclastic flows travelling down the the volcano’s slopes, and ash plumes reaching 4.5km above its summit. There are also reports of lava flows at the summit crater.

Mt Semeru is one of the most active volcanoes in Java, with activity taking place in 74 of the past 80 years. The volcano’s current eruptive phase began in 2014[6], with frequent emissions of ash plumes to hundreds of metres above the crater, pyroclastic flows and glowing lava avalanches.

Buildings and infrastructure buried by volcanic material and debris from the eruption of Mt Semeru (source BNPB Twitter).

Unexpected larger-scale eruption

But Saturday’s eruption was, unexpectedly, much larger than the ongoing background of activity. The Head of the Geological Agency of the Ministry of Energy and Mineral Resources, Eko Budi Lelono, said a thunderstorm and persistent rain had eroded part of the volcano’s lava dome[7] – a “plug” of solidified lava at the summit. This caused the dome to collapse, triggering the eruption.

Lava dome collapse is a common trigger of volcanic eruptions, and has been behind some of the deadliest eruptions in history. Collapse of the unstable dome of solidified lava is rather like taking the top off a fizzy drink bottle, depressurising the system and triggering an eruption. Lava domes sometimes collapse under their own weight as they grow, or they can be weakened by external weather conditions, as was evidently the case at Mt Semeru.

Mt Semeru eruption
The eruption was triggered by the collapse of the lava dome at Mount Semeru’s summit. Hendra Permana/AAP Image

The fact that Saturday’s eruption was triggered by an external factor, rather than conditions inside the volcano, would have made this event harder to forecast.

Volcano monitoring typically relies on signs of increased unrest inside a volcano. Increased earthquake activity can be a sign that magma is moving around beneath the ground. Another warning sign is a change in the temperature or type of gases emitted. Sometimes, small changes in the shape of the volcano or lava dome can be detected on the ground or from satellites.

Another fatal, hard-to-predict explosive eruption happened in 2019[8] at Whakaari (White Island) in New Zealand. That event was thought to have been driven by an explosion of pressurised steam rather than by magma, which made it challenging to predict.

Read more: Why White Island erupted and why there was no warning[9]

Living with active volcanoes

As the world’s population grows, more and more people are living close to active volcanoes. According to one estimate, more than a billion people[10] (14% of people on the planet) live within 100km of an active volcano.

In Indonesia, more than 70% of the population live within 100 km one or more of the country’s 130 active volcanoes – that’s a staggering 175 million people. More than 8.6 million[11] Indonesians live within 10km of an active volcano – well within range of deadly pyroclastic flows.

Read more: Under the volcano: predicting eruptions and coping with ash rain[12]

Active volcanoes monitored by the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM). Curent eruptive activity is noted by the erupting volcano symbols at Mt Merapi (orange) and Mt Semeru (yellow) in Java.

The fertile soils typically found near volcanoes mean these communities need to balance their livelihoods with the risks. Keeping an eye on dozens of active volcanoes poses a continuous challenge to Indonesia’s volcano monitoring and disaster management authorities.

References

  1. ^ 22 people (bnpb.go.id)
  2. ^ 5,000 people (twitter.com)
  3. ^ pyroclastic flows (www.nationalgeographic.org)
  4. ^ lahars (www.usgs.gov)
  5. ^ reported (magma.vsi.esdm.go.id)
  6. ^ 2014 (volcano.si.edu)
  7. ^ lava dome (volcano.oregonstate.edu)
  8. ^ happened in 2019 (theconversation.com)
  9. ^ Why White Island erupted and why there was no warning (theconversation.com)
  10. ^ more than a billion people (www.mdpi.com)
  11. ^ 8.6 million (www.cambridge.org)
  12. ^ Under the volcano: predicting eruptions and coping with ash rain (theconversation.com)

Read more https://theconversation.com/mount-semerus-deadly-eruption-was-triggered-by-rain-and-storms-making-it-much-harder-to-predict-173240

Times Magazine

Headless CMS in Digital Twins and 3D Product Experiences

Image by freepik As the metaverse becomes more advanced and accessible, it's clear that multiple sectors will use digital twins and 3D product experiences to visualize, connect, and streamline efforts better. A digital twin is a virtual replica of ...

The Decline of Hyper-Casual: How Mid-Core Mobile Games Took Over in 2025

In recent years, the mobile gaming landscape has undergone a significant transformation, with mid-core mobile games emerging as the dominant force in app stores by 2025. This shift is underpinned by changing user habits and evolving monetization tr...

Understanding ITIL 4 and PRINCE2 Project Management Synergy

Key Highlights ITIL 4 focuses on IT service management, emphasising continual improvement and value creation through modern digital transformation approaches. PRINCE2 project management supports systematic planning and execution of projects wit...

What AI Adoption Means for the Future of Workplace Risk Management

Image by freepik As industrial operations become more complex and fast-paced, the risks faced by workers and employers alike continue to grow. Traditional safety models—reliant on manual oversight, reactive investigations, and standardised checklist...

From Beach Bops to Alpine Anthems: Your Sonos Survival Guide for a Long Weekend Escape

Alright, fellow adventurers and relaxation enthusiasts! So, you've packed your bags, charged your devices, and mentally prepared for that glorious King's Birthday long weekend. But hold on, are you really ready? Because a true long weekend warrior kn...

Effective Commercial Pest Control Solutions for a Safer Workplace

Keeping a workplace clean, safe, and free from pests is essential for maintaining productivity, protecting employee health, and upholding a company's reputation. Pests pose health risks, can cause structural damage, and can lead to serious legal an...

The Times Features

Duke of Dural to Get Rooftop Bar as New Owners Invest in Venue Upgrade

The Duke of Dural, in Sydney’s north-west, is set for a major uplift under new ownership, following its acquisition by hospitality group Good Beer Company this week. Led by resp...

Prefab’s Second Life: Why Australia’s Backyard Boom Needs a Circular Makeover

The humble granny flat is being reimagined not just as a fix for housing shortages, but as a cornerstone of circular, factory-built architecture. But are our systems ready to s...

Melbourne’s Burglary Boom: Break-Ins Surge Nearly 25%

Victorian homeowners are being warned to act now, as rising break-ins and falling arrest rates paint a worrying picture for suburban safety. Melbourne residents are facing an ...

Exploring the Curriculum at a Modern Junior School in Melbourne

Key Highlights The curriculum at junior schools emphasises whole-person development, catering to children’s physical, emotional, and intellectual needs. It ensures early year...

Distressed by all the bad news? Here’s how to stay informed but still look after yourself

If you’re feeling like the news is particularly bad at the moment, you’re not alone. But many of us can’t look away – and don’t want to. Engaging with news can help us make ...

The Role of Your GP in Creating a Chronic Disease Management Plan That Works

Living with a long-term condition, whether that is diabetes, asthma, arthritis or heart disease, means making hundreds of small decisions every day. You plan your diet against m...