Mount Rinjani is 3,726 m, the second highest volcano in Indonesia, second only to Mount Kerinci on Sumatra, and it dominates the landscape of the relatively small island of Lombok.
Within its huge 50 km² caldera sits the crater lake Segara Anak (Child of the Sea). Eruptions within the caldera have formed a new small cone called appropriately enough, Gunung Baru (New Mountain). Segara Anak has a natural hot spring.
The mountain and its satellites form the Mount Rinjani National Park - officially 41,000 hectares within the park boundaries and a further 66,000 hectares of protected forest outside.
Gunun Rinjani National Park lies within the major transition zone(Wallaceae) where the flora and fauna of South East Asia makes a dramatic transition into that which is typical of Australasia. The Park has a rich variety of plants and animals, although they can be hard to spot due to the terrain and rainforest cover.
Sometimes seen early in the mornings is the rare black Ebony leaf monkey, known locally as Lutung.
TheLong tailed grey macaque or Kera is common in Lombok and older males are seen on the crater rim. Rusa deer are forest dwellers and are occasionally seen along the Rinjani trek trail. The smaller Barking deer or Kijang has an alarm call with a distinct dog-like bark. Look for the disturbed ground where the Wild pig or Babi hutan has been foraging. Also found in the forest is the Leopard cat or Bodok alas, Palm civet or Ujat and Porcupine or Landak.
A variety of colourful birds live in the forests of the Park. Perhaps the best-known icon of the Park is the Sulphur Crested Cockatoo that is not found any further west of Lombok. Many of the forest-dwelling animals, insects, birds, civets and monkeys owe their survival to the wild fig tree or Beringin as a provider of food and shelter. The pine-like Casuarina species, Cemara, are a feature of the grassy higher slopes. Orchids or Anggrek are also a feature of the grassland areas, as is Edelweiss or Bunga Abadi growing above the tree line; it is a beautiful icon of the Park and one of our best-known sub-alpine plants.
Rinjani Trek Centre: The Centre is located at the trailhead above Senaru traditional village and Rinjani Information Centre located at Sembalun Lawang village. They offer information and displays for visitors on the trek, the National Park, Sasak culture and a range of activities available in Senaru.
In 2008, the Indonesian government proposed to UNESCO that Mount Rinjani be one of the world's official geoparks. If this was approved by UNESCO, Mount Rinjani would become the first such geological park in Indonesia.
This mount is a very active volcano. The oldest recorded historical eruption was in 1847. Previous to that this was a very remote region indeed, hence the lack of records.
There was a spate of activity from 1994 to 1995 which resulted in the further growth of the crater cone Gunung Baru, since renamed Gunung Barujari (Finger Mountain).
On 27 April 2009 Gunung Barujari became active again with that activity continuing through to May 2009. The summit ascent routes were closed at that time as the eruptions intensified with plumes of smoke and ash as high as 8,000 m. A Volcanic Explosivity Index (VEI):2 rating was issued for the activity between May and December 2009. The ascent routes re-opened on September 14th 2009 but hiking routes down into the crater lake were still deemed unsafe and remained closed.
The lower and mid levels of the mountain are quite heavily forested. Above the tree line though the slopes are barren and rugged scree slopes and volcanic rock. The views of the crater lake are quite breath-taking from the caldera rim, as is the sunrise. From the absolute peak you can see Bali to the west and Sumbawa to the east.
The lower and middle elevation slopes are densely forested with typical tropical species, including species which occupy the Wallacea transitional region between the SE Asian and Australasian flora. Fig trees are especially apparent in the lower forests, as are the giant Syzigium Jambu, with the gnarled and epiphyte-hung Engelhardia Bak Bakan becoming prominent in the higher elevations. Casuarina woodland (cemara) takes over higher up and eventually these give way to an alpine flora above the treeline.
Lombok is East of the Wallace Line and some bird species with Australasian affinities are therefore apparent. These include honeyeaters, cockatoos and green hanging parrots, in addition to species whose heartland is to the West including tits, weavers and tailor-birds. Bird life can be difficult to observe here due to the density of the forest, though if you have patience and are practised at mimicry many species can be tempted out from cover - if you have the time to spare and the forebearance of your trekking partners.
The familiar long-tailed grey macaque (the Bali temple monkey) is common right up to the crater rim. Of much more interest is the rare ebony leaf monkey which inhabits these forests and whose soft hooting contact call often provides a soothing backdrop to the birdsong. Rusa deer and muntjacs are more often heard than seen.
Rinjani is best climbed during the April-November dry season. The trekking trails are generally closed during the rainy season. In recent years the early months of the 'dry season' have become more prone to rain and you should be prepared to encounter heavy rain and low visibility with slippery tracks underfoot at any time, particularly in the afternoon.
It gets very cold on the mountain above 2,000 m and nears freezing at the summit. Warm clothing is an absolute must.
Most visitors arrive via the village of Senaru (600 m), on the northern side of the mountain and thus closer to the main resort areas of the west coast including Sengingi . The other possible entry point is Sembalun Lawang (1,150 m), on the eastern side, which is closer to the summit.
Both villages are accessed from the main north coast road.