Mount Marapi eruption: what is cold lava and how does it form?

An active volcano in Indonesia has started erupting – but it’s not the burning hot lava that authorities are most worried about.

Indonesia’s national disaster mitigation agency, BNPB, has issued a warning about the risk of “cold lava,” saying it could be even more dangerous than the searing hot molten rock spewing out of the volcano.

But, what is cold lava and why is it so dangerous?

WHAT IS COLD LAVA?
Called “lahar” in Indonesian, cold lava is a phenomenon that occurs when rain mixes with volcanic materials like ash, sand and pebbles. The mixture forms a concrete-like substance that destroys everything in its path.

Rain can carry cold lava down the slopes of a volcano during an eruption and into the path of nearby towns or villages. According to the United States Geological Survey, cold lava has the power to crush and bury things in its path. It also moves quickly like wet concrete and is considered more destructive than hot lava.

“People are urged to stay away from river areas that originate from the Marapi volcano and be on alert to the potential dangers of lahar that could occur, particularly when it rains,” BNPB spokesman Abdul Muhari said in a volcano warning issued to Indonesians.

MOUNT MARAPI ERUPTS
Mount Marapi in western Indonesia began spewing what is now a two kilometre ash cloud into the sky on Thursday.

Authorities created a 4.5km exclusion zone around the volcano to protect nearby residents.

Residents were warned to wear face masks to protect themselves from falling ash and told to clear any ash from their roofs to prevent collapse.

A warning was also issued for pilots to avoid going near the ash cloud.

“Ash cloud moving to northwest. Volcanic ash is observed to be grey. The intensity of volcanic ash is observed to be thick,” the alert from Indonesia’s Multiplatform Application for Geohazard Mitigation and Assessment (MAGMA) read.

“Eruption and ash emission is continuing.”

MAGMA said the cloud wasn’t likely to impact Australia because it was travelling in a northwest direction.

RING OF FIRE
Mount Marapi translates from the local Minang language of Indonesia as “Mountain of Fire’’ and is one of Indonesia’s most active volcanoes.

Indonesia has frequent volcanic activity due to its position on the Pacific “Ring of Fire,” a 40,000 km long belt of active volcanoes where several tectonic plates come together, causing eruptions and frequent earthquakes. National Geographic states that 75 per cent of Earth’s volcanoes are located along the Ring of Fire.

Mount Marapi erupted in December last year. Sadly, 24 climbers were killed at the time of eruption and a further 60 people lost their lives when heavy rain brought cold lava into nearby districts.

POLL

GLOSSARY

• disaster mitigation: protecting people and properties from emergencies
• originate: comes from
• exclusion zone: an area around a hazard where people aren’t allowed to go, designed to keep people out of harm’s way
• tectonic plates: slabs of rock and earth that make up the outer layer of Earth, the lithosphere. These plates can move and grind against one another, causing earthquakes and volcanic eruptions

EXTRA READING
Iceland volcano still spewing lava
Icelandic volcano erupts and stuns
Boom time: hot facts about volcanoes

QUICK QUIZ
1. What is cold lava?
2. What makes cold lava so destructive?
3. How large is the ash cloud from Mount Marapi’s eruption?
4. What does the name “Mount Marapi” mean in the Indonesian language of Minang?
5. What is the Pacific “Ring of Fire”?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Warning!
It is vitally important that the danger of the cold lava is communicated clearly to all who could be impacted. Design a community announcement poster to warn residents and tell them what they need to do. Ensure your poster will grab their attention and be easily understood by all. Use simple and direct language as well as visuals to support the message.

Time: allow 30 minutes to complete this activity
Curriculum Links: English

2. Extension
Write a short announcement that can be broadcast to the public as an additional way of communicating the danger to residents.

Time: allow 15 minutes to complete this activity
Curriculum Links: English

VCOP ACTIVITY
Wow word recycle
There are plenty of wow words (ambitious pieces of vocabulary) being used in the article. Some are in the glossary, but there might be extra ones from the article that you think are exceptional as well.

Identify all the words in the article that you think are not common words, and particularly good choices for the writer to have chosen.

Select three words you have highlighted to recycle into your own sentences.

If any of the words you identified are not in the glossary, write up your own glossary for them.

Extension
Find a bland sentence from the article to up-level. Can you add more detail and description? Can you replace any base words with more specific synonyms?

Down-level for a younger audience. Find a sentence in the article that is high level. Now rewrite it for a younger audience so they can understand the words without using the glossary.