Rain Caused Volcano to Erupt… Because Climate Change?

Guest “Did you ever play the telephone game?” by David Middleton

Hat tip to Ted…

Message: Please find a qualified geologist to take on this nonsense.

They cite “the conversation” as their authority.

Today is Tuesday. Welcome to Equilibrium, a newsletter that tracks the growing global battle over the future of sustainability. Subscribe here: thehill.com/newsletter-signup.

Thunderous rains were responsible for the deadly eruption that killed at least 22 people near Indonesia’s Mount Semeru over the weekend, nonprofit journalism site The Conversation reported.

The rain collapsed the stony “lava dome” that plugged the peak of the already rumbling volcano, with effects similar to shaking up a fizzy drink and removing the cap, according to The Conversation.

The fatal eruption also damaged 3,000 buildings, while blanketing some villages in up to 13 feet (4 meters) of volcanic debris — a disaster that highlights the risk to the roughly 1 billion people worldwide who live within 60 miles of an active volcano.

WUWT Tip submission

WTF does a volcanic eruption have to do with sustainability? Volcanic soils are often extremely fertile… Think coffee. Living near a volcano is a dicey proposition… Always has been, always will be. While they didn’t expressly blame this on climate change, it’s pretty clear that the context (“Equilibrium, a newsletter that tracks the growing global battle over the future of sustainability”) is climate change and/or anti-capitalism.

When I read the article on The Hill website, the first thing that came to mind was the Telephone Game.

How to Play the Telephone Game

Co-authored by wikiHow Staff
Last Updated: September 16, 2021

The game of telephone is a classic ice breaker and party game. It’s easy to set up and a lot of fun to play. You and your friends will try to pick a word or phrase, “pass it on” by whispering it to someone next to you, and have fun seeing how much it changed during the game. All you will need to play is a couple of friends, a word or phrase, and a quiet whisper.


According to The Hill authors, Sharon Udasin (BA in French & English, MS in Journalism) and Saul Elbein (unspecified degree in Humanities & Journalism), “thunderous rains were responsible for the deadly eruption.”

Phys.org republished The Conversation article…

DECEMBER 7, 2021

Mount Semeru’s deadly eruption was triggered by rain and storms, making it much harder to predict
by Heather Handley, The Conversation

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


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, with frequent emissions of ash plumes to hundreds of meters above the crater, pyroclastic flows and glowing lava avalanches.

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—a “plug” of solidified lava at the summit. This caused the dome to collapse, triggering the eruption.



According to Heather Handley (PhD in Volcano Geochemistry), “a thunderstorm and persistent rain had eroded part of the volcano’s lava dome… This caused the dome to collapse, triggering the eruption” of “one of the most active volcanoes in Java, with activity taking place in 74 of the past 80 years.

While “triggering” might not be the most accurate word to use here, the collapse of lava domes quite frequently precedes eruptions of active volcanoes, as Ms. Handley goes on to discuss…

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.


This is from Smithsonian Institution’s Global Volcanism Program:



8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)

PMVBG reported collapses of the lava dome in Semeru’s Jonggring Seloko Crater and SE-flank flow during 1-6 December. On 1 December material collapsed from the unstable distal end of a 1-km-long lava flow in the SE-flank Kobokan drainage, sending a pyroclastic flow 700 m down the valley. Subsequent avalanches were recorded by the seismic network that day and on 3 December were not visually confirmed, likely due to several days of rainy conditions. At 1330 on 4 December the seismic network recorded avalanche signals. A larger collapse began at 1447 was seen by an observer at the Mount Semeru Volcano Observation Post and identified in data collected by PVMBG. Avalanches of incandescent material from the summit dome and SE-flank lava flow descended 500-800 m. Pyroclastic flows were visible at 1510 descending the Kobokan drainage and a sulfur odor was noted. At 1520 a large pyroclastic flow produced a large roiling and expanding ash cloud that eventually rose to 15 km (50,000 ft) a.s.l. Reports from residents described darkness from airborne ash and rainy/foggy conditions. Pyroclastic material was deposited in two districts in the Lumajang regency, and eight districts in the neighboring Malang regency were covered with ash. Preliminary estimates suggested that deposits extended at least 16 km SE from the summit.

According to the Darwin VAAC satellite observations acquired at 1630 showed a detached ash cloud drifting SW at an altitude of 15 km (50,000 ft) a.s.l. At 1740 the ash cloud continued to drift SW and a second ash cloud was drifting W at 9.1 km (30,000 ft) a.s.l. The second ash cloud had detached by 1840. On 5 December satellite images showed the two ash clouds still drifting SW and W, and possible diffuse ash emissions rising to 4.6 km (15,000 ft) a.s.l.; ash had dissipated by 1000.

Following the 4 December pyroclastic flow Badan Penanggulangan Bencana Daerah (BPBD) issued a warning to residents to stay away from drainages due to lahar hazards and began evacuating people in high-risk areas. Ten people trapped in a building could not be reached because of scalding hot deposits but were later rescued. Almost all of the houses in the Curah Kobokan area had been destroyed, mainly by pyroclastic flows, though some residents reported roof collapses from ashfall. One area of Curah Kobokan was inundated by hot lahars that took down trees. Pyroclastic flows also destroyed the Gladak Perak bridge, 13 km SE of the summit, which linked residents of Pronojiwo and Lumajang; the national road leading to Malang was blocked by tephra and fallen trees. According to news articles and BNPB, by the next day 14 people were confirmed to have died, 57 had been injured and taken to hospitals (more than a dozen of were in critical condition due to severe burns), and at least seven residents and sand miners working along the river in Curah Kobokan were missing. About 1,300 people had relocated to evacuation centers or alternative housing.

Additional pyroclastic flows during 5-6 December descended 2-3 km SE, and incandescent avalanches descended 500 m. At 0855 on 6 December a pyroclastic flow traveled 4 km down the SE drainage, temporarily halting rescue and recovery efforts. Later that day, the head of BNPB, police officers, and others conducted a 15-minute overflight of Curah Kobokan and observed steam plumes rising from the deposits. Initial estimates were that 2,970 houses and 38 educational facilities across several sub-districts in Lumajang Regency had been destroyed or damaged by the pyroclastic flows. Authorities also traveled to the fallen bridge and other nearby locations, noting damaged vegetation, fallen trees, and volcanic deposits up to 30 cm thick along the road.

By 7 December an estimated 4,250 residents were displaced in about 20 evacuation centers; most people originating from the Lumajang Regency and fewer from the Malang and Blitar regencies. The number of fatalities reached 34, with another 22 people missing. Search efforts focused on the villages of Renteng, Sumberwuluh, and Kobokan Curah, but daily afternoon rains hampered rescue and recovery efforts.

Geological Summary. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)Badan Nacional Penanggulangan Bencana (BNPB)National Public Radio (NPR)BBC NewsEarth Observatory of Singapore, Remote Sensing Lab

Global Volcanism Program, 2021. Report on Semeru (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 December-7 December 2021. Smithsonian Institution and US Geological Survey.

We’ve gone from “thunderous rain” suddenly causing the eruption of an otherwise peaceful volcano to one of the most active volcanoes, in a very volcanically active area, in a place where it rains a lot, erupting after several days of heavy rain.

This is what the mostly peaceful volcano was doing a year ago…

“Sentinel-2 thermal satellite images of Semeru on 21 November (left) and 21 December (right) 2020 showing incandescent avalanches of material descending the SE flank. A white gas-and-steam plume accompanies the avalanche on 21 December. Intermittent incandescent avalanches were observed throughout the reporting period on clear weather days. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.”
“Photo of ash deposits on 2 December 2020 in Lumajang, Indonesia, due to the eruptive events at Semeru. Some deposits damaged machinery, agricultural fields, and affected livestock. Photo by Antara Foto/Umarul Faruq; courtesy of Reuters.” https://volcano.si.edu/volcano.cfm?vn=263300
“Photo of a lahar down the Kobokan drainage on the SE flank of Semeru at 0939 on 30 December 2020. A pyroclastic flow was also observed traveling 3.5 km down the Curah Kobokan River drainage. Courtesy of BNPB.”
“hoto of an incandescent avalanche of material descending the SE flank at Semeru on 17 January 2021. Incandescence and a gray ash plume are also visible in the summit crater. Photo by Agus Harianto; courtesy of AFP/Getty Images.”

“Thunderous rains were [NOT] responsible for the deadly eruption.”

On 1 December material collapsed from the unstable distal end of a 1-km-long lava flow in the SE-flank Kobokan drainage, sending a pyroclastic flow 700 m down the valley. Subsequent avalanches were recorded by the seismic network that day and on 3 December were not visually confirmed, likely due to several days of rainy conditions. At 1330 on 4 December the seismic network recorded avalanche signals. A larger collapse began at 1447 was seen by an observer at the Mount Semeru Volcano Observation Post and identified in data collected by PVMBG. Avalanches of incandescent material from the summit dome and SE-flank lava flow descended 500-800 m.

Global Volcanism Program, 2021. Report on Semeru (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 December-7 December 2021. Smithsonian Institution and US Geological Survey.

Rain and the erosion caused by runoff played a role in the collapse of an unstable lava dome, releasing a pyroclastic flow from an extremely active volcano that was already erupting.


Global Volcanism Program, 2021. Report on Semeru (Indonesia) (Bennis, K.L., and Venzke, E., eds.). Bulletin of the Global Volcanism Network, 46:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN202104-263300

Global Volcanism Program, 2021. Report on Semeru (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 December-7 December 2021. Smithsonian Institution and US Geological Survey.

Global Volcanism Program, 2013. Volcanoes of the World, v. 4.10.3 (15 Oct 2021). Venzke, E (ed.). Smithsonian Institution. Downloaded 09 Dec 2021. https://doi.org/10.5479/si.GVP.VOTW4-2013.

Global Volcanism Program, 2013. Semeru (263300) in Volcanoes of the World, v. 4.10.3 (15 Oct 2021). Venzke, E (ed.). Smithsonian Institution. Downloaded 09 Dec 2021 (https://volcano.si.edu/volcano.cfm?vn=263300). https://doi.org/10.5479/si.GVP.VOTW4-2013

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Tom Halla
December 9, 2021 2:08 pm

It erupted because someone offended Gaia. Or was it Pele?

Reply to  Tom Halla
December 9, 2021 2:46 pm

Maybe it was Gaia’s husband, Uranus.

Reply to  Tom Halla
December 9, 2021 8:47 pm

They didn’t meet the quarterly quota of sacrificing virginal human lives for social, redistributive, and fair weather causes.

Reply to  n.n
December 9, 2021 10:56 pm

Down by Mt. Merapi the locals sacrifice a goat to appease the gods, even though most attest to being moslem.

Carlo, Monte
December 9, 2021 2:20 pm

Somewhere there is a photo I took a long time ago of Colima in Mexica venting; it was impressive to see, but nothing as dramatic as these of Semeru.

Zig Zag Wanderer
December 9, 2021 2:41 pm

Even if this were true, which it obviously isn’t, having multiple smaller eruptions is far preferable to having fewer larger eruptions. Ask the inhabitants of Pompeii. Oh, you can’t…

Nicholas McGinley
Reply to  Zig Zag Wanderer
December 9, 2021 5:42 pm

Well, we can ask any of the people who did not live near volcanoes that erupted near them, thousands of years ago.
Yeah, we cannot, and it has nothing to do with volcanoes, or how big an eruption was.

Zig Zag Wanderer
Reply to  Nicholas McGinley
December 9, 2021 7:17 pm

Have we passed peak humour?

Dave Fair
December 9, 2021 2:43 pm

The telephone game gives you “the white fog” from “the white dog.” CliSciFi misdirection gives you “climate disaster” from “climate change.”

Reply to  Dave Fair
December 11, 2021 2:08 pm

More like “climate disaster” from “natural variability”.

Zig Zag Wanderer
December 9, 2021 2:44 pm

mostly peaceful volcano


Rud Istvan
December 9, 2021 2:45 pm

The sustainability gang beclown themselves yet again.
Same as claiming renewables can supply a sustainable grid.
Same as claiming clear cutting US hardwood forests to fuel DRAX is sustainable.
Only problem is, their sustainability scam isn’t sustainable.

Reply to  Rud Istvan
December 9, 2021 8:52 pm

Au contraire, while the faith persists, the profits are green and renewable.

Joseph Zorzin
Reply to  Rud Istvan
December 10, 2021 2:50 am

“Same as claiming clear cutting US hardwood forests to fuel DRAX is sustainable.”
But of course it is- those forests have been managed for centuries. What makes you think it’s not sustainable? And, I’ve tried explaining here several times that THE FORESTS ARE NOT CLEAR CUT TO PRODUCE PELLETS FOR DRAX. They are managed for multiple products, mostly to produce high quality timber for construction and furniture. Lower value wood goes to the pulp producers for paper or to the firewood market. What’s left- and there is always something left- that goes into pellet production. Of all the wood cut in the US south, only 3% goes into pellet production. This massive hatred of forestry makes no sense in a forum for people who like fossil fuels. Forestry people LOVE fossil fuels. They can’t do their work without vast amounts for their huge trucks, for logging machinery, for the various mills. Forestry folks tend to be conservative, guys who like guns, guys who voted for Trump. So, what gives with the forestry hating here? The fact that it is indeed renewable doesn’t make it part of the “green” gang of wind and solar scams- just because fat and dirty Mickey Moore said so.

Furthermore, when you clearcut ANY forest- guess what, they grow back just fine. The greens HATE forestry and want to lock up all the forests.

Emily Daniels
Reply to  Joseph Zorzin
December 12, 2021 6:34 am

I’ve been wondering about this. I read that Drax burns about 6 million tonnes of wood pellets each year. Can managed forests really produce that much wood waste in a typical year? If more such plants were built, how many could reasonably be supplied with just the waste/leftovers?

Robert of Texas
December 9, 2021 2:49 pm

I knew it! Global warming *IS* melting mountain tops! If it hadn’t snowed in Hawaii and put out that volcano there is no telling how much damage it would have done! (<– Yes, continuing sarcasm from another article)

Peter Wells
Reply to  Robert of Texas
December 9, 2021 3:14 pm

See? All our fault for causing global warming, so they got rain instead of snow in Indonesia!

Geoff Sherrington
December 9, 2021 3:08 pm

The rainfall done it guess fails unless there was navy rain at the elevation of the peak, some 10,000 feet up above the plains.
It is common for such peaks to be higher than tropical rain clouds.
So, was there a rain gauge on top of the peak, or some other way to record heavy rain there?
If not, you can’t blame rain as an aid to eruption. Geoff S

Rud Istvan
Reply to  Geoff Sherrington
December 9, 2021 4:10 pm

Another tiny fact problem. True lava plugs are not easily eroded by rain. Prof is Kilauea Hawaii. Pretty hard rock once cooled.
Ash plugs, sure. Especially if the summit cone was mostly cinder/ash.

John Tillman
Reply to  Rud Istvan
December 9, 2021 4:30 pm

Please quit making sense. You will be consigned to the lowest circle of un-Wokeness.

Nicholas McGinley
Reply to  Rud Istvan
December 9, 2021 5:44 pm

I cannot help thinking that anything that can be dissolved by a few days of rain…which falls in droplets weighing a gram or so…is not doing much to plug up a volcanic vent under extreme enough pressure to cause a massive eruption.

Nicholas McGinley
Reply to  Nicholas McGinley
December 9, 2021 5:46 pm

It can rain as hard as possible for a week and it will not even wash away a single truckload of loose sand dropped into a 6′ high pile.
Some of it near the bottom where rivulets form, yes.
The rest gets packed more tightly togeter.

Reply to  Rud Istvan
December 10, 2021 12:22 pm

This is an incomprehensibly ignorant statement: “Heather Handley (PhD in Volcano Geochemistry), “a thunderstorm and persistent rain had eroded part of the volcano’s lava dome… This caused the dome to collapse, triggering the eruption””

As Rud says, rocks of a lava dome do not erode much at all. Ash deposits, yes, but solidified rocks, No.

It’s an active volcano with on-going eruptions, which means magma is constantly moving upward beneath/within the volcano edifice. Movement of magma deforms the edifice, including lava domes and whatever else is in the summit caldera, leading to rockfalls and other slumping within the caldera. HHandley refers to this as “collapse”, an overly dramatic phrasing, but this has nothing to do with “triggering” the eruption.

The eruption event was already beginning (magma moving) and the rising magma creates its own fracture network to the surface, gas exsolves from the magma under reduced lithostatic pressure, and bingo! – eruption.

The rain is coincidental/irrelevant. Rain on mountain slopes in the tropics – everyday. Add a bunch of steam and ash, and volcanoes create their own thunderstorms within and along with the rising eruption column.


Nicholas McGinley
Reply to  Geoff Sherrington
December 9, 2021 6:02 pm

“It is common for such peaks to be higher than tropical rain clouds.”

Yeah, right.
Stop making stuff up.
Tropical rain clouds commonly extend from sea level to 80,000 feet, poking out of the highest part of the troposphere at times.
There are no mountains that are high enough to be “higher than rain clouds”, unless they are instead snow clouds.
In fact, most rain in the world starts as ice crystals…snow…before it melts on the way down.
The interior mountains on the island of Java are characterized as “high altitude rainforest”.
Air forced over the mountains, or forced to rise from thermal heating of the ground surface, condense into clouds that grow into thunderstorms, everywhere in Java.
There are rainforests everyplace up there but where it has recently been buried by fresh flows or ash fall.
Even surrounding the active vents.
So, no…that volcano is not in any way “above the rain”.

Semeru is the highest peak on the island, and is not-above-the-rain 12,060′ at the top.

Nicholas McGinley
Reply to  Nicholas McGinley
December 9, 2021 6:39 pm

Here is a view of the volcano from satellite…which shows, as does the one in Dave’s article, that the place is obviously not “above the rain clouds”.

Which honestly is not a thing, unless, as I noted, it is so high the precip falls as snow.

The erosion gullies are plainly visible right up to the peak.
Rain forest grows within a few thousand feet, horizontally, from the peak.
Fingers of green forest cling tenaciously to life even within adjacent fresh flows…because it is so damn wet and so damn hot.
For the record, it is well known that the snow line near the equator is about 15,000 feet, and rises to about 18,700 feet near the Himalayas, which are near the Tropic of Cancer, or about 23.2° north latitude.
It never freezes even at the top of the highest peak on Java.

Semeru Satellite.PNG
Geoff Sherrington
Reply to  Nicholas McGinley
December 9, 2021 10:38 pm

Mt Semeru is a quite isolated conical peak above the plains, like a few other volcanos on the island. You do not have the common geography of a long coastal mountain range uplifting wet ocean winds in the way that many of us regard as usual or customary..There is not much land sticking up in the sky to influence rain, above intermediate altitudes like 5,000 feet.
Sure, I have flown many air miles and have an appreciation of how high tropical clouds can and do rise, thousands of feet above our Cessna Citation altitude ceiling at times. I have also lived a couple of decades in the tropics and viewed tropical clouds.
I am not saying that the top of Mt Semeru will always be in rain clouds when it rains, only that sometimes it will not be and we need to know which for the author’s hypothesis to be verifiable..
My point is, we do not have a common type of geography, so we should use caution before we say that certain conditions could and did apply.
So, what was the measured rainfall at the top of Mt Semeru at material times?
Or are people just inventing the likelihood of heavy rain affecting an eruption there, when eruptions are not unusual for this volcano in recent times and can probably happen with or without rain. Geoff S

Kit P
December 9, 2021 3:15 pm

Many years ago I took a class called Environmental Geology. There were case studies of disasters that were made worse by man not taking into account geology.

Since the university was down wind of Mt St Helens and a nuke plant, most of the students were familiar that that event. I was also there for for three others thanks to my travels in the navy.

The curse of being in nuclear power is listening to idiots. This course helped. In one case, I pointed to a geologic feature. That was a landslide. Then I pointed to the closest hill. That is a landslide that has not happen yet. Maybe you should live closer to the nuke plant.

In other case, I was standing by the tree line. My wife’s anti nuke friends came to see what I was looking at. How can you live some place and not know you have a view of Mt Rainier?

That’s an active volcano with a massive glacier. If the blast wave does not kill you the mud flow will.

This is also evidence that we are still in an ice age and a short time ago from a geologist viewpoint almost glaciers were not confined to mountain tops. Massive lava flows are everywhere in the region.

I spend summers in a place with a tsunami evacuation plan.

Not too worried about the climate in 100 years.

Reply to  Kit P
December 10, 2021 8:32 am
December 9, 2021 3:19 pm

I heard of Earthquakes caused by more water volume in the oceans (melting glaciers, polar cap, etc), but this is a new one.

Ok, make sure Greta is still a virgin and let’s sacrifice her to appease the gods.

Mick O'Keefe
Reply to  Pauleta
December 9, 2021 3:36 pm

Why would just one virgin appease a god, when he/she/ze gives way 72 of them to every jihadi when they turn up in the hereafter?

(Mind you, I’ve always questioned their inventory control and product returns systems.)

Reply to  Mick O'Keefe
December 9, 2021 5:27 pm

That was a typo. It was supposed to be 72 vegans.

Reply to  H.R.
December 9, 2021 10:48 pm

An Islamic friend of mine said it was changed to one 72yr old virgin … to put the young extremists off.

Reply to  Mick O'Keefe
December 9, 2021 11:10 pm

The 72 virgins won’t be what they think…

Reply to  Pauleta
December 9, 2021 5:07 pm

Nah, they’d just rhrow her back!

Reply to  Pauleta
December 10, 2021 4:54 am

comment image

Moderately Cross of East Anglia
December 9, 2021 4:19 pm

It was probably a snowfall that triggered the eruption of Krakatau, once East of Java before climate change caused it to slide westwards, but please don’t tell anyone.

Gary Pearse
December 9, 2021 4:37 pm

A ‘lot’ of rain measured up against the magnitude of the forces acting in a large active volcano is a piddle in the ocean. Entire solid volcanic throat plugs hundreds of meters long get blown out and broken up by explosive pressures, sometimes blown out one side of the cone. Krakatoa exploded and lofted

The cone is largely pyroclastics ‘cinders’ with ‘rays’ of lava supporting it. It is not mechanically strong. I climbed Wase Rock in Nothern Nigeria with an expert English climber in the mid 1960s – a volcanic neck or volcanic plug left after the cone erodes away. Imagine a rainstorm doing something to this relatively small plug:

comment image

Krakatoa blew away an entire island, replacing it with deep seawater filling the collapsed caldera beneath. It lifted some 20 cubic km of material into the sky. Sumera is active annually so there isn’t much of a plug formed to blow away. The rain was inconsequential. Seawater flowing into a newly collapsed caldera into the magma chamber, now that is something else!

Gary Pearse
Reply to  Gary Pearse
December 9, 2021 4:39 pm

Oops …and lofted 20 cubic km of material into the sky.

Reply to  Gary Pearse
December 10, 2021 2:21 am

Not the entire island, just the southern half, the northern half is still there. I used to go past it once a week.

Chris Hanley
December 9, 2021 4:39 pm

The Conversation:

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

The Conversation article is incoherent, if external factors like heavy rain are known to sometimes trigger eruptions as the article states, generally that should make eruptions more predictable.

Reply to  Chris Hanley
December 9, 2021 11:01 pm

“The Conversation article is incoherent”

many are

They claim “Academic rigour, journalistic flair” but the group-think mentality usually results in BS

Iain Russell
December 9, 2021 4:53 pm

The West is doomed! Utter pap!

December 9, 2021 5:03 pm

Oh, no, no, no! It all makes sense now!! No, really – it does! Because rain is what triggers climate change and climate change triggers rain…. or something like that.

Now, if you believe that, I have a drawbridge on the Potomac I’d like to sell you.

These people who come up with this stuff should stick to writing novels…. except that even those will likely be unbelievable, too.

Ron Long
December 9, 2021 5:40 pm

Thanks for the posting, David. So a pyroclastic eruptive sequence gets a lot of rainfall, and you get , first, hot lahars, then, second, cold lahars. There are reports of people being burned, but that is probably some from pyroclastic flows, which usually kill living things straight out, and some from hot lahars. I flew through (below the crater rim, south to north) the Mt. St. Helens crater, past the dome undergoing steam explosions, and then down the Toutle River as a cold lahar flowed down it. My Economic Geology Professor, Cy Field, and his son were in the back seat, and my brother (500 missions in a Birddog in Vietnam) flew the airplane.

Clyde Spencer
Reply to  Ron Long
December 9, 2021 9:10 pm

I thought only presidents, who are not indispensable, were allowed to fly close to the crater.

Ron Long
Reply to  Clyde Spencer
December 10, 2021 5:58 am

Actually, Clyde, several USGS types were shouting at us on the radio but geologists need to see things for themselves.

Michael in Dublin
December 9, 2021 6:07 pm

When someone cannot get their opinions published as science, they go to The Conversation which then suddenly gives it scholarly credibility. Any critical reader will soon notice it is a third rate source.

Clyde Spencer
Reply to  Michael in Dublin
December 9, 2021 9:12 pm

“Conversation” and “authority” in close proximity in the same sentence constitutes an oxymoron.

Nicholas McGinley
December 9, 2021 6:17 pm

What are they suggesting?
The entire island of Java is a tropical rainforest climate with significant rain in every month of the year…and has been so for tens of millions of years.
So just what exactly are they claiming has changed there?
It rains hard all the time there, always has.
But they get some clown to assert that rain caused a sudden and “unexpectedly large” volcanic eruption, and that is all it takes for the crack team of experts at The Conversation to make up a whole storyline about rain causing volcanoes to have massive eruptions?

I invite those jackasses to continue to be the jackasses they are, so as to hasten the day when every rational person in the known universe recognizes them for the absolute fools they truly are.

Koppen climate zones. AF, Tropical rainforest, shown in Red on this map, includes the entire island of Java, which I have circled for the geographically challenged.

Koppen map-Java.png
Clyde Spencer
Reply to  Nicholas McGinley
December 9, 2021 9:14 pm

But they get some clown …

I think that should be “clownette.”

Peta of Newark
December 9, 2021 7:35 pm

The thinking there, that the rain set off the volcano, is or would have been that of really really primitive times and people.
(I use the word ‘primitive’ to mean folks our ancestors from a long time ago – they were *not* primitive, otherwise we’d not be here talking)

What happened there is that the Rain God had had a disagreement with the Volcano God and the eruption was the 2 of them having a brawl and poor hapless Earth God caught the brunt and was dumped upon.
It’s that simple and commentators here have worked it out already via The Virgin Greta

IOW: Climate Science (Rain God) has had ruck with Real Science (Volcano God) and made a horrible mess of the land/houses/fields and forests (Earth God)

Perfectly describes what’s going on doncha tink…..

That kinda gives cause for real hope and optimism because the volcano is Fertility Itself (Fountains of Ambrosia as I describe them) – thus Earth God will grow back ever stronger

Ain’t that nice and ever so neat: Greta (bless her) is trying to set off the eruption that will cover the lands of Earth (God) with fertility
Personally I’d save Greta from a fiery end and ask a few miners, quarry operators and farmers to mash up some old frozen basalt and spread it around with a tractor.

but hey ho, each to your own

edit to PS
wot did i say or what did i mean – ‘do please everyone keep your own fiery ends away from the virginal greta or it’ll all go wrong. OK?’

Tony H
December 9, 2021 10:17 pm

I have a different theory on what triggered this eruption. It occurred within 15 minutes of new moon when the moon was also at perigee, ie tidal forces were about as big as they get (this only occurs about once every 14 months). Few volcanologists acknowledge that tidal forces trigger volcanoes, but after studying the timing of eruptions for many years I believe that they do. This one also occurred in the middle of the day when the moon and sun were more or less directly overhead when tidal forces were at their maximum.

Joel O'Bryan
December 9, 2021 10:37 pm

The telephone Game:

First person: “Before Climate Change t’was global warming.”

eventually morphs to become: “Biden’s diaper change is quite alarming.”

James Walter
December 10, 2021 12:26 am

Well, it is climate change – caused by the grand solar minimum – which causes increase high energy radiation – all part of Little Ice Ages

Tom Abbott
December 10, 2021 4:46 am

How does the lava dome stay in place if the volcano is erupting all the time?

Reply to  Tom Abbott
December 10, 2021 8:44 am

Life cycle of a dome in an active stratovolcano like this can be pretty short. Dome is extruded following an explosive eruption. Dome grows for a while. Gets big enough, and is too structurally unstable to remain in shape. Collapses downhill, forming a pyroclastic flow. As it is actively growing via more magma being extruded up the conduit, that stream is uncapped, and you get an explosion. Sometimes the explosion destroys the dome causing the collapse.

Highly variable process based on gasses dissolved in the magma and viscosity of the magma itself. Leads to a boatload of what-ifs.

Your clue on Semeru is its shape. You don’t maintain that shape on a young stratovolcano for long, as the material that makes the cone is soft and unstable – layered lavas, tephras, pyroclastics – all subject to gravity. You get flank collapses – hot and cold, landslides, debris flows, and in wet areas, lots and lots of lahars. This part of Indonesia is way wet.

Looks like this one was a two-fer with a twist – a dome collapse / pyroclastic flow and lahar. The twist are multiple collapse of the end of a lava flow out of the crater causing smallish pyroclastic flows to start the festivities. Lahars don’t generally require an eruption, but eruptions can cause them. All in all, a fascinating puzzle. Cheers –

Good sources for info on Semeru are

Smithsonian GVP – https://volcano.si.edu/volcano.cfm?vn=263300

MAGMA Indonesia is their functional equivalent – https://magma.vsi.esdm.go.id/

Cheers –

Tom Abbott
Reply to  agimarc
December 10, 2021 6:23 pm

Thanks for the comment.

gary mankiewicz
December 10, 2021 11:08 pm

Come on people ACID rain is BACK!

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