BJ Deming

Mount Merapi (Indonesia)

Here’s another Decade Volcano eBook chapter, rewritten and included for free on my Patreon. As mentioned last week, that’s where I’ll be publishing “The Supervolcanoes and Us” so if you like this blog, why not support the free posts here by joining me on Patreon and getting those exclusives?

This view, by rdt radihan/Shutterstock, of a split-topped volcano, covered with vegetation and rising out of a jumble of sharp-edged green hills is wild and pretty, isn’t it?

For a little color contrast, just add a thin ribbon of incandescent red lava coming down the emerald green hillside — no, wait. Let’s not do that.

There are anywhere from 900 to 1900 people per square kilometer (0.4 mi2) living on that pretty green mountain despite the volcano’s activity (as indicated by a faint plume rising above its summit in the image). (Mei et al.; Thouret et al., 2000)

It’s impossible to keep people away from Gunung Merapi, “Mount Fire Mountain” in the local language.

All told, per Thouret et al. (2000), more than a million of them live and work, mostly in agriculture, on this 9,700-foot-tall volcano.

Millions more live at its feet as well as in nearby Yogyakarta, a major city/sultanate whose downtown area is less than twenty miles south of Merapi’s smoking summit.

That tropical greenery is not a wilderness — most of it is under cultivation.

Usable land is so scarce on central Java that hundreds of small farming villages, and their associated fields, pastures, stock pens, and plantations, occupy the lower two-thirds of this very active Decade Volcano. (Thouret et al., 2000)

Good news: The chances of a lava flow reaching them are slim, since Merapi’s lava is too sticky to travel far from the crater. (Voight et al.)

Bad news: People are still at risk.

Above the villages and the vegetation towers Merapi’s stark summit, where vegetation cannot survive because lava domes frequently form there and then collapse, sending down pyroclastic flows.

Other volcanoes do that, too, but our Decade Volcano is the namesake for “Merapi-type” dome collapse/pyroclastic flow behavior. It constructs a new lava dome every four to six years on average. (Darmawan et al.; Gertisser et al., 2012; Lavigne et al., 2018; Thouret et al., 2000)

Each dome sheds multiple pyroclastic flows, so Mount Merapi’s hazardous summit is uninhabited and officially is a Forbidden Zone.

When the volcano is quiet, many people tend to take this more as a suggestion than a rule, with the occasional inevitable surprise (media reported that everyone on Merapi that day escaped unharmed).

And some 80,000 miners haul sand off those flow fields daily. (Nossin; Voight et al.)

Sand miners?

Are there also light-saber duels in the summit crater when an eruption’s on?

Here’s a close-up look of one of the summit domes to help you enjoy that pleasant fantasy.

The real-life reason for the video at that link is cool, too, although written as a technical paper — it’s explained in this abstract.

Miners come into the story of Merapi because there is a global sand shortage due to the huge demand for high-grade silica in electronics manufacturing.

Most beach and desert sand doesn’t have the right qualities to be turned into microchips, etc. Volcanic ash does, and it’s therefore a valuable global commodity.

High prices, plus some harsh economic realities locally, mean that sand miners will do their thing despite the hazards at this productive volcano, both up at the summit AND in dry river channels down below, which are prone to sudden flows.

Sure, this is inexcusably risky, but it’s not done carelessly. Miners make much more money than farmers can earn, when the volcano allows it, and to some Javanese that’s a worthwhile gamble.

Sand miners occasionally lose the gamble and their equipment and/or lives, but the volcano often does allow coexistence.

Sometimes, though, Merapi gets nasty — then all bets are off.

If monitoring showed that a strong eruption might be on the way, what arguments would you use to convince these hardscrabble residents and miners to evacuate?

Force seems to have only worked once: for the Japanese Army in 1943, during its occupation of Java in World War II, per Voight et al.

As we’ll see in the 2010 eruption section, Indonesian scientists and emergency officials manage the situation with a combination of intensive volcano monitoring; hazard mapping; a four-level volcanic alert system (Mount Merapi often is at Level 3, the next-to-highest level); public outreach, especially in high-risk communities; and in-depth advance crisis planning by authorities from the village level all the way up to national decision makers.

This volcano emergency system for Gunung Merapi, with roots in the International Decade and even farther back, isn’t perfect, of course, but it saves lives, including tens of thousands of lives saved in 2010 during the worst eruption that Merapi has yet thrown at the modern world. (Mei et al.; Pallister et al.; Surono et al.)

No one has forgotten that terrible time.

The Javanese also trust those hard-working scientists and officials because the experts know and respect local traditions. (See Newhall, 2018, for an in-depth general discussion of the importance of trust in volcanic crises.)

Tradition is a vital part of life on Java, particularly in and around Yogyakarta — a world-famous center of Javanese culture as well as the only major Indonesian city still ruled by a monarchy. (Wikipedia)

Nearby Gunung Merapi is part of the cultural scene, too.

Many of its human neighbors believe this volcano to be a sacred place that, besides threats, offers them gifts. (Mei et al.)

It even has a spiritual gatekeeper.

Mas Lurah Suraksosihono (better known as Asih) received the royal appointment after his father, gatekeeper “Grampa” (Mbah) Maridjan, died in a pyroclastic flow during the opening hours of Gunung Merapi’s unusually large 2010 eruption.

Mount Merapi is called “Mount Fire Mountain” for a reason, although it usually maintains a fairly low-key though active presence.

Gunung Merapi erupted before the Europeans came; it erupted throughout colonial times; it erupted during both World Wars; it erupted during the struggle for national independence. (Voight et al., 2000)

With all this activity, records show, Gunung Merapi has killed more than seven thousand people. (Mei et al.)

And it is still erupting today.

What is Mount Merapi?

Merapi is a young volcano, in geological terms, with an age that ranges through thousands — not millions — of years. (Gertisser et al., 2012)

This cone-shaped stratovolcano sits inside a two-mile-wide somma ampitheater that opens south and west. (Gertisser et al., 2011; Newhall et al.; Nossin; Thouret and Lavigne)

A somma!

If that doesn’t already have you thinking of some of the other Decade Volcanoes, then here’s another tie-in: Gunung Merapi, just like Mexico’s Colima, is the youngest and southernmost of a whole family of volcanoes!

As we saw in the last chapter, at Colima, north to south, it’s extinct El Cántaro, Nevado de Colima, Paleofuego (now a somma), and active Fuego de Colima. (Cortés et al.)

Here on Java, north to south, it’s Ungaran, Telomoyo, Merbabu, and Merapi. (Thouret et al., 2000; Yudistira et al.)

The difference is that Merapi’s ancestors might not be extinct, and none of them made that somma.

The mysterious somma

Merbabu, about six miles north of Mount Merapi’s summit, didn’t collapse, as did the ancient Mexican volcano Paleofuego. This means that Merbabu is not responsible for the somma around Merapi.

In fact, although volcanologists can detect no sign of molten rock under Merbabu right now — as they do at Merapi, even between eruptions — Merbabu is still with us; its last eruption was a VEI 2 in 1797. (GVP; Ramdhan et al.; Yudistira et al.)

Merbabu is also connected physically to Mount Merapi’s northern somma wall. (Selles et al.) There might even be an underground intrusive link — see Yudistira et al. for (highly technical) details.

For these reasons, some researchers call this the Merapi-Merbabu Complex.

Also, unlike Fuego de Colima’s extinct northern relatives in Mexico, Java’s Telomoyo and Ungaran, north of Merbabu-Merapi, might just be asleep, according to the Smithsonian’s Global Volcanism Program, not extinct.

Mount Ungaran even has steaming fumarole fields!

Despite these unique features, the big picture at Merapi is the same as at Decade Volcano Colima, right?

What Colima-style geological dramas have led to Gunung Merapi’s somma? What events brought the present cone into existence? What keeps perilous “Fire Mountain” burning today?

Answer to all of the above: [Crickets chirping]

Unfortunately, Merapi hides its secrets well.

It usually just sits there and rumbles at the boffins with relatively mild (VEI 1-2) lava dome-forming eruptions — it does not explain itself, nor the reason why it also goes on deadly rampages every few decades (VEI 3) to once or twice a century (VEI 4), last in 2010. (Surono et al.; Thouret et al., 2000; Webley and Watson; Widiyantoro et al.)

With millions of people at risk, no one can ignore Mount Merapi. Yet its behavior remains a mystery despite systematic work done here by Indonesian and foreign volcanologists since the late 19th century and despite the continuous record of objective observations that they have carefully kept since 1927. (OSU; Voight et al.; Wegler and Lühr)

Gunung Merapi’s designation as a Decade Volcano in the 1990s brought in even more international collaboration, as well as a major expansion of the monitoring network. (Newhall, 1996, 1999)

But earth scientists also need to see what a volcano has done over geologic time and that’s not always possible at Merapi, which sits in a tropical monsoon zone.

On central Java, heavy rainfall, erosion, sedimentation, and intense vegetation growth quickly destroy or cover up geologic evidence that the much drier tropical savanna climate around Colima Volcanic Complex has preserved for millennia.

Good luck trying to collect useful research samples from what’s left of a somma and volcanic rocks that have been exposed to the Javan elements for thousands of years!

The presence of Mount Merapi’s somma structure is clear evidence that another volcano probably stood here recently — coming after Merbabu and before Merapi — and it collapsed. (Thouret and Lavigne)

Thanks to the climate, field workers can’t find unquestionable evidence of that collapse (Newhall et al.), as they have done at Colima — or even at Mauna Loa and Teide Decade Volcanoes, where telltale fields of hummocky terrain spread out across the Pacific and Atlantic ocean floors, respectively.

Nevertheless, scientists in a variety of disciplines keep working on it. As Gertisser et al. (2011) note, understanding Mount Merapi’s past is the key to knowing what it will do in the future.

Hazards at Mount Merapi

How stable is Gunung Merapi today? Could it collapse, too?

The impression from this layperson’s reading is that no one really knows for sure, although I did see that, in 2000, Thouret et al. called for a reassessment of the west, southwest, and south flanks.

It’s not that anyone is ignoring the stability issue; research teams are probably hard at work on it.

I think it’s that short-term hazards at Merapi outweigh longer-term concerns about possible structural weakness.

As long as written records have been kept, no one has died in a flank or sector collapse here.

Gunung Merapi has used other murder tools, mainly pyroclastic density currents and volcanic mudflows. (Mei et al.; Thouret et al., 2000)

Pyroclastic flows

Technically, these are density currents, but if you suddenly yell “Pyroclastic flow!,” everybody will still scramble, as well they should.

“Pyroclastic” means “broken by fire.” “Flow” — well, you’ve probably seen video of one, internal heat making its ash clouds boil up in fantastic shapes as it races along, hugging the ground, blowing down trees and buildings, burning up everything in its path and then burying it, all in a matter of seconds.

“Race” is the right word: the flow is cushioned by hot volcanic gases that reduce ground friction that otherwise would slow the thing down.

When gas content is extra high, the resulting dilute pyroclastic flow is much more mobile and can run uphill, overtop ridges, and go in unexpected directions. (Charbonnier and Gertisser: Kelfoun et al.; Newhall et al.; Thouret and Lavigne)

A pyroclastic surge is shown crossing a ridge at around the 30-second mark in this public service video from Montserrat.

These unexpected flow movements, while rare, are the usual culprits behind mass-casualty tragedies on Merapi’s flanks.

They also are a major reason why authorities set up exclusion zones around any erupting volcano.

You can’t outrun one of these, and unless you’re lucky enough to already have a long head start when you first learn one is coming, you can’t drive out of its way, either.

That’s too bad. Intense heat and those hurricane-force winds, loaded with rock, ash, and other debris, mean that pyroclastic flows are unsurvivable. (Lavigne et al., 2018)

People coexist with them at Gunung Merapi only because the flows tend to travel just a few kilometers from the summit, after being generated in a “Merapi-style” dome collapse, and also they usually stay inside certain river drainages that everyone knows to avoid.

In a way, Mount Merapi’s human neighbors are all amateur volcanologists.

Just as they know the sun comes up in the east, they know that:

  • An eruption will begin with sticky degassed lava slowly oozing out of a vent in or around the summit crater (unlike Etna, Mount Merapi doesn’t seem to have middle or lower flank eruptions).
  • The lava then will pile up around the summit or upper flank vent as a dome.
  • As more lava oozes up, the dome will get bigger and bigger, of course, and then finally something will give way. (Kelfoun et al.)
  • Parts of the lava dome will crumble off into small pyroclastic flows that whoosh down the volcano’s flanks just as far as gravity can take the dense mixture of rock, ash, and hot gas — usually much less than 10 km from the summit at Mount Merapi.

That’s the routine here.

People lose everything, die, or are injured because Gunung Merapi, unlike the rising sun, works in an unpredictable change now and then.

Prediction would be nice, but there is no way yet for experts to see a dome collapse coming. (Darmawan et al.; Kelfoun et al.)

All they can do is respond as quickly as possible after it happens.

Sand miners are indeed flirting with death every minute that they work on those old pyroclastic and lahar flow fields.

Lahars

Pyroclastic flows are the biggest killers at Gunung Merapi, but lahars are the most common volcanic hazard. (Thouret et al., 2000)

Lahar is a local word with several meanings on Java (Pyle), but everyone drops what they’re doing and runs for high ground when they hear that one is coming.

In this gut-wrenching sense, lahar means a volcanic mudflow — a slurry of ash, boulders, debris, and water (typically rainwater at Merapi, per Lavigne et al., 2000, but elsewhere it might come from a crater lake or, as at Mount St. Helens in 1980, from melting glaciers and snow pack).

Let’s drop the italics, since volcanologists worldwide now use this term.

Near the volcano, a lahar is as thick as wet cement — it can be cold or, if it has crossed fresh pyroclastic flow deposits, scalding hot.

As this video shows, a lahar can carry boulders as it moves along. The accompanying ground shaking and noise are life-saving warnings to those downstream, but the lahar will still take out immovable objects like houses, dams, and bridges; cut transportation links; and carve new river channels through what were once villages and fields. (De Bélizal et al.)

Farther away from Merapi, after dropping much of its sediment load, the lahar — known locally as a banjir now (Voight et al.) — more closely resembles muddy water, but it can still be terrible.

Lahars happen anywhere on Gunung Merapi, even when the volcano is sleeping.

Due to weather patterns, they are most common during the rainy season (roughly November through April) and form in the wake of afternoon storms, especially in areas where a recent pyroclastic flow has destroyed or buried vegetation that was holding down soil on the fire mountain’s steep flanks. (Lavigne et al., 2000; Newhall et al.)

Once started, lahars can travel farther than pyroclastic flows do: up to 30 km (19 miles) at Merapi (Thouret et al., 2000), which puts Yogyakarta in range.

Most are much smaller than that and run out short distances. Over time, this process has built up more than 110 square miles of lahar deposits at the foot of the volcano. (Thouret and Lavigne)

These lahar gifts from Gunung Merapi — fertile soil and lodes of volcanic sand — attract people in spite of the accompanying risks.

Hundreds of thousands of people inhabit the lahar-prone areas now. (De Bélizal et al.; Lavigne et al., 2000; Selles et al.)

To protect them, Indonesia started the Mount Merapi Project in 1969, constructing a series of sabo dams — lahar flow-containment structures that were pioneered by the Japanese (who joined the project in 1977). (De Bélizal et al.; Lavigne et al., 2000; Thouret and Lavigne)

Once the upper reaches of all rivers draining Gunung Merapi were dammed this way, lahars didn’t run out as far and they were less intense. (Lavigne et al., 2000)

The death toll drop was dramatic.

According to De Bélizal et al., 38 people died in lahars in 1969; between 1987 and 2010, there were no human fatalities, although that was a costly period for sand miners, who lost almost 200 trucks to lahars.

However — foreshadowing — a sabo dam can occasionally make pyroclastic flows jump out of their usual channels and travel overland through farms and villages. (Charbonnier and Gertisser; Newhall, 2018; Surono et al.; Thouret and Lavigne)

And they are not built for extreme events.

Per De Bélizal et al., three of the 240 lahars related to Merapi’s 2010 “big one” — fortunately, small lahars at that distance — did reach Yogyakarta; closer to the volcano, lahars destroyed 14 sabo dams and 21 bridges.

Merapi, 2010

I chose not to use the “X and the Decade Volcano Program” header here because:

  • Much of the Decade Volcano work on Mount Merapi was geophysical (Newhall, 1998) and, from even the little bit that I’ve read, it goes way beyond the scope of this eBook.
  • Geoscience research in a variety of specialties did not stop when the International Decade ended.

    Studies are ongoing even today — there are so many people at risk here, and Gunung Merapi is such a tough nut to crack!

  • Last, but certainly not least, a look at the 2010 eruption shows us how scientists and the laypeople living on and around Mount Merapi handled one of the toughest post-program tests yet of advances made at a Decade Volcano.

To get a feel for those “after” results at Gunung Merapi, we need to briefly look at its “before” situation.

This is also a good time to bring in a few details of how volcanologists and authorities make decisions during a crisis that unexpectedly has gotten very deep.

Mount Merapi before and during the 20th Century

In the 1820s, pyroclastic flows and lahars destroyed 8 villages, killing more than a hundred people, while in 1872 — during Merapi’s last VEI 4 blast before 2010 — the volcano blew off its entire summit and buried all villages located more 1 km above sea level under thick pyroclastic flow deposits and layers of ash. (Brown et al.; Kelfoun et al.; Voight et al.)

As mentioned, Merapi can be very nasty.

During the twentieth century, Indonesian and international scientists kept an eye on this dangerous volcano during all ten decades of the 1900s, not just the UN-designated Nineties, and everyone in Merapi’s vicinity collected a dividend from that knowledge in late October and early November 2010.

The 1920s saw the start of continuous detailed record-keeping and systematic fumarole studies at Merapi, which slept from 1925 to 1929. (Voight et al.)

1930 was a bad year. Mount Fire Mountain, as usual, was erupting. On December 28, its large summit lava dome collapsed, sending pyroclastic flows and surges out to 12 km, killing 1,369 people. Six villages were destroyed or heavily damaged.

Then Merapi slept from 1935 to 1939. (Voight et al.)

The 1940s and subsequent decades were bad, too, but mostly for social reasons.

Japan occupied the country during World War II, and when they left at the war’s end, Indonesia declared independence and eventually won the intense military, diplomatic, and guerrilla battles that ensued. (New World Encyclopedia)

The watch on Mount Fire Mountain continued throughout this period, even though, per Voight et al., one volcanologist had to monitor Merapi as a prisoner of Japanese occupying forces; also, the Dutch sent a volcanology agency’s director, who was German, to an internment camp in British India, where he died.

During the years of political turmoil in Indonesia, Merapi’s ash plume from a VEI 3 blast in 1961 darkened a 100-mile stretch of Java’s coast as well as the sky over nearby international marine traffic lanes on the Indian Ocean.

Then came an intense rainy season, and deadly lahars in 1962. In 1963, more of Gunung Merapi’s mudflows cut important railroads between Yogyakarta and the city of Magelang — this was six years before the Japanese-Indonesian Mt. Merapi Project undertook what turned out to be very effective sabo-dam sediment control efforts.

Gunung Merapi was having one of its rare quiet spells during those lahar disasters (Voight et al.) — a reminder that volcanoes can mess you up even when they are not erupting.

In 1968, Indonesian authorities, with Japanese assistance, established the first modern seismic monitoring and event classification system at Gunung Merapi.

During the 1970s, France joined in with studies of the volcano’s gas emissions, while in the 1980s, a USGS-Indonesian project improved seismic monitoring of Mount Merapi.

Merapi slept from 1987 to 1992. (Voight et al.)

In the 1990s, Decade Volcano researchers carried forward earlier work and started new projects.

All in all, probably more international collaboration was done at Merapi during the 1990s than at any other Decade Volcano. (Newhall, 1999)

However, some volcanic events cannot be foreseen, and there was a tragedy in 1994.

That year, Gunung Merapi was having one of its typical eruptions and, as in 1930, a large lava dome collapsed. This time, the pyroclastic flows went, not to the northwest as before, but into valleys on the southwestern flank for the first time in many decades. (Charbonnier and Gertisser; Kelfoun et al.; Mei et al.; Newhall et al., 2000; Thouret et al., 2000)

Per Kelfoun et al.:

  • Two villages, more than 6 km from the summit, were wiped out.
  • Over 60 people died.
  • Six thousand fled, and given the change in run-out direction, 2,000 of them eventually needed permanent resettlement.

These new flow channels put the crowded southern slopes of the volcano at risk. Yogyakarta itself was now in Gunung Merapi’s sights! (Charbonnier and Gertisser; Darmawan et al.; Gertisser et al., 2011; Metaxian et al.; Mei et al.; Nadeau et al.; Nossin; Pallister et al.; Ratdomopurbo et al.; Thouret et al., 2000; Widiyantoro et al.)

Additionally, as the International Decade and the 20th century were winding down, better knowledge of the volcano brought up new concerns, including:

1. The debate (still going on today) over Merapi’s somma, mentioned earlier in this chapter.

2. The discovery through field work that Gunung Merapi has had ancient violent eruptions surpassing anything recorded during the 20th century.

For instance, rocky archives show that, from the 7th to 9th centuries AD (not that long ago in geological terms), Mount Merapi’s eruptions were big and explosive, with pyroclastic flows running down the southwest flank for 15 km or more! (Newhall et al.)

3. More people at risk. From the mid-1970s on, the population around and on Merapi grew at a much faster rate than the national average for a variety of social and economic reasons. (Mei et al.)

4. Finally, THE question: after about 130 years of “normal” behavior had Mount Merapi turned over a new leaf with this remarkably long stretch of low-key activity, or was it just a bit slow in building up to one of the “big ones” that historical records describe, on average, once or twice a century? (Newhall et al.; Surono et al.; Thouret et al., 2000; Voight et al.)

With scientific data only available from the 20th century, that important question had to go unanswered.

2000-2009

Not surprisingly, given its liveliness, Gunung Merapi entered the 21st century right in the middle of a typical eruption. It then dozed off to sleep in late 2002 (GVP) after having had a total of five “Merapi-style” eruptions since 1990. (Ratdomopurbo et al.)

A 2002 hazard map and its first revision (2006) were based on Gunung Merapi’s activity throughout the 20th century, which was the period of scientific observation.

It seemed, in all probability, that in the 2000’s Mount Merapi would continue the same relatively low level of activity that it had been showing for well over a century now.

But there was no guarantee. Experts could not yet completely rule out the worst-case scenario of a repeat “big one”: the VEI 4 eruption in 1872. (Newhall et al.; Thouret et al., 2000)

While emergency managers prepped and planned for what was most likely to happen next at dormant Mount Merapi, volcanologists in the early 2000s focused on that worst-case scenario.

The lack of data on one of these cataclysms was especially worrisome because Merapi happens to be an “open-conduit” volcano.

Magmatic gases escape through its vents before they can accumulate inside and cause noticeable monitoring changes that tell volcanologists the fire mountain is about to erupt. (Chaussard et al.; Surono et al.)

This is why Mount Merapi never gives much warning (Chaussard et al.), although after a century of study, geoscientists have learned to recognize the subtle signs of impending trouble.

For instance, the summit does deform a little bit as rising lava causes changes in the conduit. (Chaussard et al.; Surono et al.)

What no one knew was whether those familiar little signals would be larger when a “100-year” event was on the way and when more lead time would be needed for mass evacuations and other broad-scale measures. (Chaussard et al.; Surono et al.)

Why should those subtle warning signs be larger? Wouldn’t the open conduit keep precursors at the same low level, even before a major eruption?

That was an unsettling thought, with a million people now living on Mount Fire Mountain.

The scientific debate went on.

Then, in July 2005, the first of a series of small earthquake swarms showed up on seismic stations.

This was one of the familiar little precursors: Gunung Merapi was waking up again.

The 2006 eruption

Think of this one as a rehearsal for the big event — it certainly wasn’t totally routine.

Three or four years is a typical Merapi nap length, and seismic swarms like those that began in 2005 have preceded eruptions here since at least 1992. (Budi-Santoso et al.; Ratdomopurbo et al.; Thouret et al., 2000)

Everybody got ready, and lava finally oozed out of the volcano’s summit in April 2006 and started piling up into a dome. (GVP)

Next, as everyone knew from previous eruptions, the growing dome would crumble, spawning “Merapi-style” pyroclastic flows.

Then what?

  • Given what had happened in 1994, could any of these flows now reach the crowded south-facing flanks?
  • Evacuations would eventually be needed, but where and when?
  • How should temporary shelters for evacuees be located so that they would be close enough to reach quickly but far enough out of harm’s way so evacuees wouldn’t need to move later, if the eruption escalated?
  • Was there an app for this?

No, there wasn’t an app, but there were four volcanologists from the US Volcanic Disaster Assistance Program (VDAP) in Indonesia just then. They planned to work at another volcano, on Sulawesi.

Instead, they went to Java and assisted Indonesian volcanologists with collecting as much data on restless Gunung Merapi as possible. Since it was the rainy season, clouds often obscured the volcano’s summit. VDAP was able to arrange for commercial optical satellite imaging of Merapi’s growing dome whenever orbital schedules allowed and the view from space was reasonably clear. (ESRI; Pallister et al.; Relief Web)

The VDAP workers also teamed up with the Indonesian government, using GIS technology and databases to identify areas most likely to be affected. In 2010, this work would be the basis for official decisions on evacuations and shelter locations. (ESRI)

Some good news soon became apparent.

The 2006 summit dome had formed north of an intracrater wall of hardened lava from 1910 that could redirect dome-collapse pyroclastic flows to the uninhabited west and southwest flanks! (GVP)

As long as that wall stood (note: foreshadowing), it shielded the densely populated southern flanks.

The volcano nevertheless had unpleasant surprises for its human neighbors:

Satellite imaging of Merapi’s summit showed that lava was coming up very quickly during the 2006 eruption. (Pallister et al.)

By May 22, 2006, about 2.3 million m3 of semi-molten lava rock was sitting in the summit crater, and some 22,000 people down below had been evacuated. (GVP)

No one wanted to see a repeat of the calamitous 1930 and 1994 oversized dome collapses.

Then, on May 27, a major tectonic earthquake, centered just south of Yogyakarta, hit.

Besides killing almost 6,000 people and causing massive regional destruction, the temblor also seemed to affect nearby Merapi — but not the way you might think.

That summit dome didn’t collapse — not then — but the volcano’s lava eruption rate doubled, at least. (GVP)

Volcanologists had to wonder: Could this be how an 1872-type eruption starts?

While lacking any direct data from way back then, VDAP and Indonesian volcanologists ran what they had — a century’s worth of careful observations — through the computers to do an “event-tree” statistical analysis.

It showed only a 10% chance that this was about to escalate into a “big one.” (Pallister et al.)

And, as things turned out, Merapi did not go big-time in 2006. It had an almost typical VEI 1 eruption. (GVP)

Yay!

But the eruption destroyed that natural wall at the summit that protected communities on Merapi’s southern flanks. It also carved a big canyon into Mount Merapi’s southeast flank that led straight into the populated Gendol drainage. (GVP; Pallister et al.; Ratdomopurbo et al.)

After June 14, Mount Merapi’s activity level began to drop, although pyroclastic flows continued until July and, starting on June 16, a new dome began growing in the summit crater. (GVP)

Also on the 16th, the first-ever satellite image of a moving pyroclastic flow was obtained. (Thouret et al., 2010)

Of note, Gunung Merapi’s next eruption, at the start of the 2010 rainy season, would mark another space-age first: the first time that satellite observations played an equal role with traditional geophysical and geochemical methods in monitoring an eruption. (Charbonnier and Gertisser; Pallister et al.; Surono et al.)

Contingency planning

By the second half of 2007, this eruption was over. (GVP)

I’m not sure if Gunung Merapi went completely dormant afterwards.

Gertisser et al. (2011) mention low-level activity, while the Global Volcanism Program lists 2008 in brackets with mention of a single volcanic ash advisory from Darwin VAAC.

Certainly everyone in the area could now take a breather.

As mentioned above, the hazard map was revised to take into account the changes wrought in 2006.

Districts used that revised map for their contingency planning exercises in 2009.

According to Table 2 in Mei et al., the planning involved various eruption scenarios with pyroclastic flow run-out distances that ranged from 7 km out to 10, 12, and even 15 km — the longest reach of 20th-century pyroclastic flows.

Evacuation shelters were established at a reasonable distance — more than 15 km, but less than 20 km away from Mount Fire Mountain. (Mei et al.)

Research projects continued on Mount Merapi, and starting in July 2009, more seismic stations were added to its field network.

At the end of October 2009, monitoring instruments picked up a familiar little precursor — the first of what would be four earthquake swarms through June 2010.

Many people probably said to themselves, “Here we go again.”

They would have been right, if any of them had been around in 1872.

2010

As the earthquake swarms continued into 2010, authorities held public meetings in high-risk communities, getting everyone ready for another eruption. In addition, about 2,000 people in Zone III practiced emergency drills from May 30 to June 1. (Mei et al.)

As the months passed, Mount Fire Mountain seemed to be following its usual pre-eruption wind-up.

In early September 2010, more familiar little signals of an impending eruption appeared, and on September 20, CVGHM raised the four-step alert level from 1 (normal) to 2 (increased activity) — a heads-up for everyone in Zone III to be more aware of the volcano and what it was doing. (Budi-Santoso et al.; Mei et al.)

That same day, unexpectedly, all monitored values at Gunung Merapi soared and its fumarole chemistry drastically changed. (Budi-Santoso et al.; Surono et al.)

More magma than usual appeared to be on the way, but it was still many miles below the summit. (Budi-Santoso et al.)

Harmonic tremor showed up on seismic stations near the summit for a few days, starting on September 30th.

Overall, though, it seemed to be the onset of a typical Merapi eruption.

Then, on October 17, the frequency and energy of those earthquakes increased exponentially. Their centers were rapidly moving closer and closer to the surface, too. Fumarole temperatures began to soar, and the volcano’s summit warped out of shape much faster and farther than usual. (Budi-Santoso et al.; Surono et al.)

Whether or not anyone realized it yet, Gunung Merapi was answering that question about precursor size before one of its “big ones.”

CVGHM went to level 3 alert (prepare to evacuate Zone III) on October 21 and requested VDAP assistance on the 22nd. (Pallister et al.; Surono et al.)

Starting on October 23, the volcano began spouting small steam/ash plumes from its summit. (GVP)

Tremor now saturated some seismometers near the summit, with the largest earthquakes centered just a few hundred feet below the crater. (Budi-Santoso et al.)

This continued on the 24th, and Merapi’s summit inflation increased. (Budi-Santoso et al.; GVP; Mei et al.)

Monday, October 25

At 6 p.m., local time, CVGHM called a level 4 alert, requiring evacuation out to 10 km from the summit — aaaand, nobody left (except those with special needs, children, and some of the elderly). (Budi-Santoso et al.; GVP; Mei et al.)

Mei et al. note that this is what people on Mount Fire Mountain typically do — the “amateur volcanologists” wait until there is ashfall or a pyroclastic flow.

At this point, the volcano showed no visible sign of its inner turmoil, other than those little plume spurts.

Then, at 9:42 p.m. — literally out of left field if you were facing north — came a magnitude 7.7 earthquake, centered almost 750 miles to the west, near the Mentawai Islands off Sumatra’s western coast. (Satake et al.)

It generated a huge tsunami, killing more than 500 people and displacing thousands more. (GVP; Satake et al.)

In that remote region, it would be weeks before rescuers could reach all the affected areas.

And, hundreds of miles to the east, on Java, Gunung Merapi stayed quiet.

Tuesday, October 26

At dawn, Merapi just showed a thick steam plume rising from its summit. (GVP)

The day was ordinary — apart from all the bad earthquake/tsunami news out of Mentawai — until around 5 p.m. Then national attention suddenly shifted to central Java as Gunung Merapi’s summit exploded, shooting a column of ash seven and a half miles into the sky. (Pallister et al.; Surono et al.)

Thousands of people, who had probably been expecting the usual appearance of lava oozing out to build a dome, poured off the mountain.

Volcanologists, already hard at work, knew that Merapi had never started an eruption explosively during the era of scientific monitoring. This very well could be a “big one”! (Surono et al.)

In a small village about 7 km from the summit, Merapi’s spiritual gatekeeper, Mbah Maridjan, who once had been injured by a pyroclastic flow, refused to leave.

This village had not experienced pyroclastic flows in the past and it was not very close to a river drainage.

He felt that his place was on the mountain at a time like this.

As many as 34 people refused his advice to evacuate and stayed at his side.

Summit explosions continued. Pyroclastic flows generated by those blasts, and perhaps also by the collapsing initial eruption column, contained enough gas to not only race about 8 km down the Gendol and two other river drainages but also to surge overbank and cross the land in between rivers. (Gertisser et al., 2012; Pallister et al.)

They swept through the gatekeeper’s village soon after he had turned away would-be rescuers (in that linked video, see how that rescue worker keeps looking up as he washes the windshield? He is only a few miles away from and just several hundred feet below Merapi’s exploding summit vent, in full roar no doubt, though the sirens drown it out. In the dark.)

Police and military teams retrieved the gatekeeper and his companion’s bodies the next day. (GVP; Mei et al.; Subandriyo et al.; Surono et al.)

Wednesday, October 27 to Tuesday, November 2

Indonesia was now dealing with two major disasters — the Mentawai quake/tsunami and an unusually violent eruption near Yogyakarta.

Fortunately, Mount Merapi quieted down a bit for the next two days, but people nearby were busy.

Refugees crowded the roads, rescuers brought out the dead and injured, and scientists tried to predict Merapi’s next move.

As time passed, some evacuees briefly returned home to check on things (Mei et al.), while volcanologists studied high-definition images of the volcano’s summit; VDAP had been able to arrange for radar-capable satellite coverage that could “see” through volcanic plumes as well as weather clouds. (Budi-Santoso et al.; Pallister et al.; Surono et al.)

Other satellites took Merapi’s temperature and measured its SO2 and other gas emissions. (Pallister et al. USGS)

This was possible only because a number of international satellite-use protocols had been invoked. Experts at volcano observatories in Italy and the United States also joined in to help analyze the resulting flood of data, usually within two to six hours of acquisition, sending their results to CVGHM as soon as possible. (Pallister et al.; Surono et al.)

Meanwhile, what seismic instruments were left after the initial blasts occurred now showed that Mount Fire Mountain was shaking as gas and magma moved through it. Then the volcano had three more big explosions on October 29, October 30, and November 1. (Surono et al.)

November 1st satellite images showed that Gunung Merapi had grown a new dome. Lava was pouring out of the summit even faster than it had in 2006. In just four days, the lava dome’s estimated volume reached about 5 million m3. (Pallister et al.)

On the human side, contingency plans were working, and more than 53,000 people were now in shelters. (Mei et al.)

But Merapi was not yet done with fireworks.

Wednesday, November 3

High-frequency tremor reappeared on seismometers and the frequency of pyroclastic flows picked up, particularly down the south flank. (Budi-Santoso et al.; Charbonnier and Gertisser)

Soon the volcano was once more in full eruption, with waves of explosions and powerful outgassing saturating seismic stations. CVGHM extended the evacuation zone from 10 km to 15 km, doubling the number of refugees. (Surono et al.)

An hour and a half after the zone was extended, pyroclastic flows ran out to 12 km and Merapi’s violent spasms continued unabated. (Surono et al.)

The Climax: November 4-5

By Thursday, November 4, tremor was saturating seismic stations and, as the day went on, it increased so much that ground 9 miles away from Merapi was shaking as if in a Mercalli II to III earthquake. (Pallister et al.)

Satellite closeups continued to show lava coming up out of the summit at rates that were orders of magnitude faster than in 2006.

In the face of Merapi’s “big one,” CVGHM made a tough decision — they told everyone up to 20 km from the summit to leave immediately. (Pallister et al.)

What made this tough was that it tossed contingency planning right out the window. Everyone in temporary shelters had to move, since they were all within 20 km of the violent volcano.

And central Yogyakarta was now only 5 km outside the new line.

This was all less urgent than getting everyone as far away from Merapi as possible before it went into what was shaping up to be the climactic blast.

In those last few, chaotic hours before the final paroxysm, almost everyone did get away, but hundreds were still caught when the great blast and dome collapse came, around midnight, sending pyroclastic flows 16 km down the Gendol drainage, filling in valleys and surging cross country. (Charbonnier and Gertisser; Gertisser et al., 2011; Mei et al.; Pallister et al.)

As November 5, 2010, dawned, more than a quarter million Javanese were displaced. Although Merapi now began to wind down (eventually returning to Level 1 in September 2011), refugee numbers peaked on November 14, 2010, at almost 400,000. (GVP; Mei et al.)

Mount Merapi killed close to 400 people in that VEI 4 eruption, most of them caught in pyroclastic surges more than 12 km away from the volcano, while they were evacuating at the last minute. (Subandriyo et al.; Surono et al.)

The toll would have been much higher without the timely evacuations. As it was, more than 2,200 buildings out to 16 km were destroyed by pyroclastic flows, and the terrain up there was completely reshaped. (Subandriyo et al.; Surono et al.)

Lahars during the eruption killed 3 people and afterwards, in the heavy 2010-2011 rains, injured another 15. Those post-eruption volcanic mudflows also wrecked or heavily damaged 860 houses; and as mentioned earlier, they took out 21 bridges as well as 14 sabo dams. Lahars also cut roads between Yogyakarta and other regional cities multiple times and buried more than 170 acres of farmland. (De Bélizal et al.)

While associated costs were awful, there should have been tens of thousands of casualties, given the number of people in harm’s way in 2010.

While discussions about this continue, authors of all the expert papers I have read agree that the relatively low death toll was due to:

  • The country’s in-depth knowledge of Mount Merapi thanks to almost a century of careful monitoring.
  • The increased knowledge and monitoring capabilities that happened at this Decade Volcano from the mid-1990s on.

Merapi did the same thing after its 2010 blasts that it had done after a similar tantrum in 1872: it dozed off to sleep for a couple years, awoke with some steam and phreatomagmatic explosions, and then in August 2018, went back into the low-level dome-building/collapse/pyroclastic flow business. (GVP; Métaxian et al.)

The question remains — will another “big one” happen here in our lifetime, or was that it for the 21st century?

Only time can tell.

Stats:

Location:

7.54°S, 110.446° E, on Java in Indonesia. The GVP Volcano Number is 263250.

Nearby Population:

Per the Global Volcanism Program website:

  • Within 5 km (3 miles): 49,205
  • Within 10 km (6 miles): 185,849
  • Within 30 km (19 miles): 4,348,473
  • Within 100 km (62 miles): 24,728,414

CURRENT STATUS:

At the time of writing, Aviation Code Orange, Level 3 on a four-point alert system.

Monitoring:

  • MAGMA Indonesia official activity notices.
    (As of February 19, 2025, no active notices are in effect; daily updates are obtained most easily through the MAGMA ID app, though that is in Indonesian.)
  • Darwin VAAC (this site’s advisory page is difficult to reach at times; no advisories are in effect at this time).

Sources:

  • Brown, S.K.; Jenkins, S.F.; Sparks, R.S.J.; Odbert, H.; and Auker, M. R. 2017. Volcanic fatalities database: analysis of volcanic threat with distance and victim classification. Journal of Applied Volcanology, 6: 15.
  • Budi-Santoso, A.; Lesage, P.; Dwiyono, S.; Sumarti, S.; and others. 2013. Analysis of the seismic activity associated with the 2010 eruption of Merapi Volcano, Java. Journal of Volcanology and Geothermal Research, 261: 153-170.
  • Charbonnier, S. J., and Gertisser, R. 2012. Evaluation of geophysical mass flow models using the 2006 block-and-ash flows of Merapi Volcano, Java, Indonesia: Towards a short-term hazard assessment tool. Journal of Volcanology and Geothermal Research, 231: 87-108.
  • Chaussard, E.; Amelung, F.; and Aoki, Y. 2013. Characterization of open and closed volcanic systems in Indonesia and Mexico using InSAR time series. Journal of Geophysical Research: Solid Earth, 118(8): 3957-3969.
  • Cortés, A.; Komorowski, J. C.; Macías, J. L.; Capra, L.; and Layer, P. W. 2019. Late Pleistocene-Holocene debris avalanche deposits from Volcán de Colima, Mexico, in Volcán de Colima: Portrait of a Persistently Hazardous Volcano, 55-79.
  • Darmawan, H.; Troll, V. R.; Walter, T. R.; Deegan, F. M.; and others. 2022. Hidden mechanical weaknesses within lava domes provided by buried high-porosity hydrothermal alteration zones. Scientific Reports, 12(1): 3202.
  • De Bélizal, E.; Lavigne, F.; Hadmoko, D. S.; Degeai, J. P.; and others. 2013. Rain-triggered lahars following the 2010 eruption of Merapi volcano, Indonesia: A major risk. Journal of Volcanology and Geothermal Research, 261: 330-347.
  • ESRI. 2009. GIS versus the volcano. https://www.esri.com/news/arcnews/spring09articles/gis-versus-the-volcano.html
  • European Volcanological Society (SVE). n. d. Decade volcano program 1990/2000. http://www.sveurop.org/gb/program/program.htm
  • Fearnley, C.; Winson, A. E. G.; Pallister, J.; and Tilling, R. 2018. Volcano crisis communication: challenges and solutions in the 21st century. Observing the Volcano World: Volcano Crisis Communication: 3-21. https://link.springer.com/chapter/10.1007/11157_2017_28
  • Gertisser, R.; Charbonnier, S. J.; Troll, V. R.; Keller, J.; and others. 2011. Merapi (Java, Indonesia): anatomy of a killer volcano. Geology Today, 27(2): 57-62.
  • Gertisser, R.; Charbonnier, S. J.; Keller, J.; and Quidelleur, X. 2012. The geological evolution of Merapi volcano, central Java, Indonesia. Bulletin of Volcanology, 74: 1213-1233.
  • Global Volcanism Program: Mount Merapi weekly activity reports and bulletins. https://volcano.si.edu/volcano.cfm?vn=263250
  • Harijoko, A.; Marliyani, G. I.; Wibowo, H. E.; Freski, Y. R.; and Handini, E. 2023. The geodynamic setting and geological context of Merapi volcano in Central Java, Indonesia, in Merapi Volcano: Geology, Eruptive Activity, and Monitoring of a High-Risk Volcano, 89-109). Cham: Springer International Publishing. (Abstract only.)
  • Kelfoun, K.; Santoso, A. B.; Latchimy, T.; Bontemps, M.; and others. 2021. Growth and collapse of the 2018–2019 lava dome of Merapi volcano. Bulletin of Volcanology, 83: 1-13.
  • Lavigne, F.; Thouret, J. C.; Voight, B.; Suwa, H.; and Sumaryono, A. 2000. Lahars at Merapi volcano, Central Java: an overview. Journal of Volcanology and Geothermal Research, 100(1-4): 423-456.
  • Lavigne, F.; Morin, J.; Mei, E. T. W.; Calder, E. S.; and others. 2018. Mapping hazard zones, rapid warning communication and understanding communities: Primary ways to mitigate pyroclastic flow hazard. Observing the Volcano World: Volcano Crisis Communication: 107-119. https://link.springer.com/chapter/10.1007/11157_2016_34
  • Lowenstern, J. B.; Ewert, J. W.; and Lockhart, A. B. 2022. Strengthening local volcano observatories through global collaborations. Bulletin of Volcanology, 84(1): 10. https://link.springer.com/article/10.1007/s00445-021-01512-w
  • Lühr, B. G.; Maercklin, N.; Rabbel, W.; and Wegler, U. 1998. Active seismic measurements at the Merapi volcano, Java, Indonesia. Decade-Volcanoes under Investigation, Vol. Sonderband III/1998 of DGG-Mitteilungen, 53-55.
  • Lühr, B. G.; Koulakov, I.; Rabbel, W.; Zschau, J.; and others. 2013. Fluid ascent and magma storage beneath Gunung Merapi revealed by multi-scale seismic imaging. Journal of Volcanology and Geothermal Research, 261: 7-19.
  • Mei, E. T. W.; Lavigne, F.; Picquout, A.; De Bélizal, E.; and others. 2013. Lessons learned from the 2010 evacuations at Merapi volcano. Journal of Volcanology and Geothermal Research, 261: 348-365.
  • Merapi Volcano Observatory (MVO) archived pages. July 4, 1997. http://web.archive.org/web/19970704195917/http://www.vsi.dpe.go.id/mvohomepage.html
  • Métaxian, J. P.; Santoso, A. B.; Caudron, C.; Cholik, N.; and others. 2020. Migration of seismic activity associated with phreatic eruption at Merapi volcano, Indonesia. Journal of Volcanology and Geothermal Research, 396: 106795.
  • Nadeau, O.; Williams-Jones, A. E.; and Stix, J. 2013. Magmatic–hydrothermal evolution and devolatilization beneath Merapi volcano, Indonesia. Journal of Volcanology and Geothermal Research, 261: 50-68.
  • Newhall, C. 1996. IAVCEI/International Council of Scientific Union’s Decade Volcano projects: Reducing volcanic disaster. status report. US Geological Survey, Washington, DC. Retrieved from https://web.archive.org/web/20041115133227/http://www.iavcei.org/decade.htm
  • ___. 1999. IAVCEI’s Primary IDNDR Project: Decade Volcanoes. IAVCEI News 1999. 2:8-9. https://tinyurl.com/ycxtsu4h (PDF)
  • Newhall, C. 2018. Cultural differences and the importance of trust between volcanologists and partners in volcanic risk mitigation, in Observing the Volcano World: Volcano Crisis Communication: 515-527. https://link.springer.com/chapter/10.1007/11157_2016_40
  • Newhall, C. G.; Bronto, S.; Alloway, B.; Banks, N. G. and others. 2000. 10,000 Years of explosive eruptions of Merapi Volcano, Central Java: archaeological and modern implications. Journal of Volcanology and Geothermal Research, 100(1-4): 9-50.
  • New World Encyclopedia. 2019. Indonesia. https://www.newworldencyclopedia.org/p/index.php?title=Indonesia&oldid=1021356. Last accessed September 10, 2023.
  • Nossin, J. J. 2005. Volcanic Hazards in Southeast Asia, in The Physical Geography of Southeast Asia. Oxford University Press.
  • Oregon State University: Volcano World. n.d. Merapi.http://volcano.oregonstate.edu/merapi. Last accessed April 12, 2020.
  • Pallister, J. S.; Schneider, D. J.; Griswold, J. P.; Keeler, R. H.; and others. 2013. Merapi 2010 eruption—Chronology and extrusion rates monitored with satellite radar and used in eruption forecasting. Journal of Volcanology and Geothermal Research, 261: 144-152.
  • Pyle, D. 2017. Lahar: Lost in translation? https://blogs.egu.eu/network/volcanicdegassing/2017/12/14/lahar-lost-in-translation/ Last accessed September 10, 2023.
  • Ramdhan, M.; Widiyantoro, S.; Nugraha, A. D.; Métaxian, J. P.; and others. 2019. Detailed seismic imaging of Merapi volcano, Indonesia, from local earthquake travel-time tomography. Journal of Asian Earth Sciences, 177: 134-145.
  • Ratdomopurbo, A.; Beauducel, F.; Subandriyo, J.; Nandaka, I. M. A.; and others. 2013) Overview of the 2006 eruption of Mt. Merapi. Journal of Volcanology and Geothermal Research, 261: 87-97.
  • Relief Web. 2006. Indonesia: Mt. Merapi Volcano OCHA Situation Report No. 7. https://reliefweb.int/report/indonesia/indonesia-mt-merapi-volcano-ocha-situation-report-no-7
  • Satake, K.; Nishimura, Y.; Putra, P. S.; Gusman, A. R.; and others. 2013. Tsunami source of the 2010 Mentawai, Indonesia earthquake inferred from tsunami field survey and waveform modeling. Pure and Applied Geophysics, 170: 1567-1582.
  • Selles, A.; Deffontaines, B.; Hendrayana, H.; and Violette, S. 2015. The eastern flank of the Merapi volcano (Central Java, Indonesia): Architecture and implications of volcaniclastic deposits. Journal of Asian Earth Sciences, 108: 33-47.
  • Subandriyo; Gertisser, R.; Aisyah, N.; Humaida, H.; and others. 2023. An overview of the large-magnitude (VEI 4) eruption of Merapi in 2010., in Merapi Volcano: Geology, Eruptive Activity, and Monitoring of a High-Risk Volcano, 353-407. (Snippets only.)
  • Surono, M.; Jousset, P.; Pallister, J.; Boichu, M.; and others. 2012. The 2010 explosive eruption of Java’s Merapi volcano—a ‘100-year’event. Journal of Volcanology and Geothermal Research, 241: 121-135.
  • Thouret, J., and Lavigne, F. 2005. Hazards and risks at Gunung Merapi, Central Java: a case study, in The Physical Geography of Southeast Asia. Oxford University Press.
  • Thouret, J. C.; Lavigne, F.; Kelfoun, K.; and Bronto, S. 2000. Toward a revised hazard assessment at Merapi volcano, Central Java. Journal of Volcanology and Geothermal Research, 100(1-4): 479-502.
  • Thouret, J. C.; Gupta, A.; Lube, G.; Liew, S. C.; and Cronin, S. J. 2010. The 2006 pyroclastic deposits of Merapi Volcano, Java, Indonesia: High-spatial resolution IKONOS images and complementary ground based observations. Remote Sensing of Environment, 114(9): 1949-1967. Abstract only.
  • United States Geological Survey (USGS). n.d. Successful Crisis Response by Indonesia’s First-Class Volcano Response Team. https://volcanoes.usgs.gov/vdap/merapi.html Last accessed September 10, 2023.
  • ___. 2013. Merapi 2010 eruption—Chronology and extrusion rates monitored with satellite radar and used in eruption forecasting. https://www.usgs.gov/publications/merapi-2010-eruption-chronology-and-extrusion-rates-monitored-satellite-radar-and-used Last accessed September 10, 2023.
  • Voight, B.; Constantine, E. K.; Siswowidjoyo, S.; and Torley, R. 2000. Historical eruptions of Merapi volcano, central Java, Indonesia, 1768–1998. Journal of Volcanology and Geothermal Research, 100(1-4): 69-138.
  • Walter, T. R.; Wang, R.; Zimmer, M.; Grosser, H.; and others. 2007. Volcanic activity influenced by tectonic earthquakes: Static and dynamic stress triggering at Mt. Merapi. Geophysical Research Letters: 34(5).
  • Webley, P. W., and Watson, I. M. 2018. The role of geospatial technologies in communicating a more effective hazard assessment: application of remote sensing data, in Observing the Volcano World: Volcano Crisis Communication: 641-663. https://link.springer.com/chapter/10.1007/11157_2017_7
  • Wegler, U., and Lühr, B. G. 2001. Scattering behaviour at Merapi volcano (Java) revealed from an active seismic experiment. Geophysical Journal International, 145(3): 579-592.
  • Widiyantoro, S.; Ramdhan, M.; Métaxian, J. P.; Cummins, P. R.; and others. 2018. Seismic imaging and petrology explain highly explosive eruptions of Merapi Volcano, Indonesia. Scientific Reports, 8(1): 13656.
  • Wikipedia. 2020. Mount Merapi. https://en.wikipedia.org/wiki/Mount_Merapi Last accessed April 12, 2020.
  • ___. 2020. The 2010 eruptions of Mount Merapi.https://en.wikipedia.org/wiki/2010_eruptions_of_Mount_Merapi Last accessed April 20, 2020.
  • ___. 2020. Mbah Maridjan. https://en.wikipedia.org/wiki/Mbah_Maridjan. Last accessed April 12, 2020.
  • ___. 2020. Special Region of Yogyakarta. https://en.wikipedia.org/wiki/Special_Region_of_Yogyakarta Last accessed April 12, 2020./li>
  • ___. 2020. Yogyakarta. https://en.wikipedia.org/wiki/Yogyakarta Last accessed April 12, 2020.
  • Wikipedia (Indonesian). 2020. Gunung Merapi.https://id.m.wikipedia.org/wiki/Letusan_Merapi_2010. Last accessed April 20, 2020, via Google Translate.
  • ___. 2020. Mbah Maridjan. https://id.wikipedia.org/wiki/Mbah_Maridjan Last accessed April 20, 2020, via Google Translate.
  • ___. 2018. Taman Nasional Gunung Merapi (Mount Merapi National Park). https://id.m.wikipedia.org/wiki/Taman_Nasional_Gunung_Merapi Last accessed May 28, 2018, via Google Translate.
  • Yudistira, T.; Métaxian, J. P.; Putriastuti, M.; Widiyantoro, S.; and others. 2021. Imaging of a magma system beneath the Merapi Volcano complex, Indonesia, using ambient seismic noise tomography. Geophysical Journal International, 226(1): 511-523.

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