Mount Sinila is a crater in the floor of the Dieng Plateau
Mount Sinila, the name that travellers type into a search bar, belongs to a crater rather than a peak. Sinila lies in the Banjarnegara part of the Dieng Plateau, on low ground near the villages of Pekasiran and Batur, and it is one of the best-known vents in the whole Dieng Volcanic Complex. The reason is a single night in February 1979, when gas released in this part of the plateau killed well over a hundred people in and around their villages.
Anyone planning a trip to the plateau should understand this place for what it is. The tall, climbable summits of Dieng rise around the edge of the highland. Sinila is down on the low ground, among farmland and hamlets, and the danger here does not come from lava or ash. It comes from gas that seeps out of the ground and gathers where the land is lowest.
Where Sinila sits inside the Dieng Volcanic Complex
The Dieng Volcanic Complex covers an area of about six by fourteen kilometres in Central Java. It is made of two or more old volcanoes and more than twenty small craters and cones. The plateau is a high basin ringed by older volcanic ridges and dotted with lava domes, cones and explosion craters, some of which now hold lakes. The land you drive across is, in effect, a volcano that keeps erupting in small pieces rather than one great cone.
Nothing on Dieng compares with the great single-cone volcanoes of Java, which is exactly why the plateau feels so different: many small vents spread across a high, flat valley, each capable of its own small eruption or its own leak of gas. The craters are shared between three regencies, Banjarnegara, Wonosobo and Batang, and the Banjarnegara side holds many of the best known.
In the Banjarnegara section of the plateau the named craters include Sinila, Timbang, Sileri, Candradimuka and Sikidang. Some are steaming fields that visitors walk beside, while others are quiet hollows among the potato fields, and that quiet appearance is part of the danger. A crater that looks like nothing more than a damp patch of ground can still be a place where gas escapes.
The ridges around the plateau are where the real heights are. Prau, the highest point of the complex, reaches about 2,565 metres. Those ridges are where walkers climb for sunrise views, and they are a different experience from Sinila altogether. For a hike with a proper trail and a view, Mount Prau above the plateau is the better choice.
What kind of crater Sinila is
The type of eruption matters. The craters of Dieng mostly produce phreatic explosions, in which water underground meets heat from below, flashes to steam and blasts out mud, water and fragments of rock. No fresh magma needs to reach the surface. Such eruptions are sudden and short, which is why they can arrive with very little warning and why the surroundings can look entirely calm in the days before.
The craters around Sinila are known above all for gas. Carbon dioxide and hydrogen sulphide both escape from the ground here, and Timbang, a short distance from Sinila, is the crater most closely linked with toxic gas on the whole plateau. Timbang and Sinila belong together in any account of the 1979 night, because the gas that did the killing came from the Timbang side, released through cracks opened by the eruption at Sinila.
The 1979 eruption and the gas that followed
On 20 February 1979, after earthquakes that frightened the villagers, Sinila exploded. Rock and mud were thrown out, a hot mudflow ran over roads and farmland, and a second vent opened nearby in the area called Sigluduk.
The explosion was not what killed most people. The ground cracked, and carbon dioxide mixed with hydrogen sulphide escaped from the Timbang side. Carbon dioxide is heavier than air, so it did not rise and disperse. It flowed downhill toward the Batur plain as an invisible layer and settled in the low ground. People who left their houses because of the earthquakes walked into it. Most of the dead were caught on the footpath leading from the village of Kepucukan toward Batur.
Well over a hundred people died, and many more were hurt. Thousands of residents of the surrounding villages were evacuated in the days that followed. In the end the authorities closed the area around Timbang, removed Kepucukan from the map and resettled its surviving residents through the transmigration programme. The ground there is farmland today, and the name survives mainly in the memory of the disaster.
Why gas is the lasting hazard on the plateau
Toxic gas, rather than eruption, is the hazard that people on the plateau watch most closely, because the eruptions here are usually small and phreatic while gas can gather silently. Carbon dioxide has no smell and gives no sign. Hydrogen sulphide smells of rotten eggs at low levels, but at high levels it dulls the sense of smell, so the warning disappears just when it is needed. Both gases are heavier than air and settle in hollows and valleys.
Other craters have caused deaths too. Dieng has a long record of phreatic eruptions and gas releases going back centuries, and Sileri, one of the most active craters in recent years, erupted several times in 2017. In July of that year a sudden blast of mud from Sileri hit visitors who had gone close to the rim, and several of them were injured. Timbang and Sinila remain the craters most closely watched for gas.
After 1979 the response was built up over time. The volcano observation post on the plateau monitors the craters with instruments, and the volcanology agency sets exclusion zones around the active ones. Contingency plans cover Banjarnegara, Wonosobo and Batang, the three regencies that share the plateau, and they set out which villages would move where if gas or an eruption threatened them.
Reading the hazard on the ground
Alert levels on Dieng change, and the volcanology agency sets them, so the level that applied last month may not apply this week. Sileri has been put under raised alert more than once in recent years. Visitors are asked to keep well clear of the rim of any active crater, and at several craters the distance in force is hundreds of metres.
A few practical habits follow from the way the gas behaves:
- Low ground is the risk. Hollows, ditches, shallow pits and valleys are where heavy gas settles on a still day.
- Do not dig or poke at the soil near a vent. Disturbing the ground can free gas that had been held in the soil.
- Stay on higher ground and stay standing if you stop near a crater, and leave at once if you feel dizzy, get a headache or notice a sulphur smell that suddenly grows strong.
- Follow any rope, sign or local instruction. Residents know which tracks are closed.
These are not rules invented for visitors. They are the lessons that came out of 1979, when most of the dead were people moving through low ground in the dark.
The neighbouring craters worth knowing
If the aim is to see an active crater safely, the better-known sites sit on managed tracks. Kawah Sikidang is the crater field visitors reach most easily, with steaming vents and boiling mud. Kawah Sileri has been among the most active craters in recent years, and its restrictions change most often. Kawah Candradimuka is another of the named craters on the Banjarnegara side, and gas is a hazard around it. Sumur Jalatunda is a deep, well-like crater whose name means the Jalatunda well, and it is another place where visitors are asked to keep to the viewing area.
Taken together, these vents explain why the plateau has so many odd, smoking, bubbling places packed into a small area. They also explain why local guides and the volcanology agency insist on staying on marked paths and well back from crater rims.
Sinila within a visit to Dieng
The plateau also holds a cluster of small Hindu temples more than a thousand years old, concentrated around Dieng Kulon rather than near Sinila. The shrines named after heroes of the Mahabharata, the Arjuna group and the lone temple of Bima among them, are the main cultural draw; the Arjuna temple group is the place to begin. The plateau spans Batur district in Banjarnegara and Kejajar district in Wonosobo, with Batang Regency sharing its northern edge.
Sinila lies among farms and hamlets, and the ground where Kepucukan once stood is farmland today. Anyone who wants to see this part of the plateau should ask in Batur first, check the current alert level, and treat the ground around Sinila and Timbang as land to cross carefully, not to explore.
The road to the plateau climbs from the lowlands in long bends. Travellers coming from Yogyakarta or Semarang can plan the route with getting to the Dieng Plateau, and the lakes, craters and temples of the whole highland are introduced on the Dieng Plateau page.
Common questions about Sinila
Is Mount Sinila a mountain you can climb?
No. Sinila is a crater on low ground inside the plateau, among fields and hamlets. The summits that people climb on Dieng, such as Prau, rise around its edge.
Is Sinila still dangerous?
The ground around Sinila and Timbang can still release gas, and carbon dioxide can collect in low spots without any smell or visible sign. That is why the area is treated with caution and why the craters are monitored.
How many people died in 1979?
Well over a hundred people died, most of them overcome by gas while leaving Kepucukan in the dark, and many more were injured.
What happened to Kepucukan?
The village was emptied, removed from the map, and its residents were resettled elsewhere under the transmigration programme.