This national park is named after its two mountains, Mount Semeru (the highest in Java at 3,676 m), Mount Bromo (the most popular) and the Tengger people who inhabit the area.
Mount Semeru, also known as Mahameru (“Great Mountain”), is one of Indonesia’s most active volcanoes. What stands out most about this mountain is that it erupts reliably: every 20 min or so, the volcano belches out a huge cloud of steam and smoke, sometimes interspersed with ash and stones. Climbing Mount Semeru requires some planning and a permit from the national park authority. The mountain is often closed due to its highly active nature.
Mount Bromo (2,329 m) is easily recognized as the entire top has been blown off and the crater inside constantly belches white sulphurous smoke. It sits inside the massive Tengger caldera (diameter approximately 10 km), surrounded by the Laut Pasir (Sea of Sand) of fine volcanic sand. The overall effect is unsettlingly unearthly, especially when compared to the lush green valleys all around the caldera.
The major access point is Cemoro Lawang (also Cemara Lawang or Cemora Lawang – blame the East Javanese accent!) at the northeastern edge of the caldera, but there are also trails from Tosari (northwest) and Ngadas (southwest). The village of Ngadisari, on the road from Probolinggo about 5.5 km before Cemoro Lawang, marks the entrance to the national park. Both Cemoro Lawang and Ngadisari are rather picturesque, with brightly-painted houses and flower beds outside.
Every year, starting in January, climbing Semeru is prohibited for several weeks (usually more than a month) to allow the vegetation to recover.
The area in and around the park is inhabited by the Tenggerese, one of the few significant Hindu communities left on the island of Java. The local religion is a remnant from the Majapahit era and therefore quite similar to that on Bali but with even more animist elements. The Tenggerese are believed to be descendents of the Majapahit princes and were driven into the hills after mass arrivals in the area of devoutly Muslim Madurese in the 19th century. These Madurese immigrants were labourers working for Dutch coffee plantation owners and the native Hindu people of the region soon found themselves outnumbered and either converted to Islam or fled to the inhospitable high mountain tops where they remain today.
The religion is quite low key though (certainly when compared to Bali) with the most visible manifestation of faith being the rather austere Poten temple in the sea of sand. The Tenggerese number about 600,000 and they reside in 30 villages scattered in and around the park with smaller communities elsewhere in East Java.
For many visitors, the sight of the angular-faced, sunburned, moustachioed Tenggerese wrapped in poncho-like blankets, trotting about on ponies with craggy mountains as the backdrop, more resembles Peru than Indonesia!
If a landscape was ever needed to demonstrate the meaning of the phrase desolate beauty, then this is surely it. Rugged, barren volcanic peaks, gravel plains and that sea of sand. Truly unworldly.
The park also includes large areas which are very lush and green fed by rivers from the high tops. The medium elevations are clad with much thinner forest before this gives way to the barren plateau and peaks.
Flora and fauna
In the parts of the park which most interest visitors (the caldera and mountain tops) flora and fauna is limited by the general lack of vegetation. At lower elevations and away from the sea of sand, there are though lush green valleys with a typical tropical forest flora. The higher elevations before the tree line ends are largely clad with casuarina (cemara) forest.
Down in the valleys, a few leopard cats are present but rarely seen. Java rusa deer, muntjac, marbled cat and wild pig are amongst the mammals more likely to be glimpsed by casual visitors. This park is not so renowned for birdwatching as others in Java, but up on the plateau you often see hawks and eagles soaring over the valleys below.
Temperatures are refreshingly cool during the day but outright cold at night as temperatures can drop close to zero in the summer and are rarely much above 5°C in winter. Daytime temperatures anywhere in the park never exceed 20°C with low teens being normal.
It can rain at anytime and the mean average rainfall is 6,600 mm. Most of that comes in the wet season though – November to March. During periods of heavy rain in January and February especially, many parts of the park are inaccessible due to flooding. Landslips are also a real issue at these times.
The 2010/2011 eruptions
In late 2010 and early 2011 volcanic ash and incandescent material was thrown up by eruptive activity with a heavy rain of ejected volcanic material falling around the crater. Continuous eruptions on 21 January caused a thin ash fall mainly in the village area of Ngadirejo and Sukapura Wonokerto, Probolinggo district. The impact of the heavy rain and volcanic ash from eruptions during December 2010 and January 2011 resulted in disruption to normal activities and the local economy. The potential for long term environmental damage and health problems amongst the residents in the locality surrounding Mount Bromo was paramount at that time.
Due to high seasonal rainfall in January 2011 the potential for lahar (cold lava) and lava flow (hot lava) was elevated due to the deposits of volcanic ash, sand and other ejected material that thad built up. Activity was dominated by tremor vibration, eruption of ash plumes and ejection of incandescent material.
People living on the banks of the Perahu Ravine, Nganten Ravine and Sukapura River were alerted to the high possibility of lahar flows, especially if further heavy rainfalls occur in the area around Cemorolawang, Ngadisari and Ngadirejo. Eruptions and volcanic tremors were reported on 21 January and 22 January with activity subsiding on 23 January 2011.
The park was reopened to visitors in April 2011.