Rinjani Mountain or Gunung Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara (NTB). It rises to 3,726 metres (12,224 ft), making it the second highest volcano in Indonesia, and similar in height to Mount Fuji, the third highest mountain of the Indonesian archipelago and the thirty ninth most prominent peak in the world.
The first historical eruption occurred in September 1847. The most recent eruption of Mount Rinjani was in May 2010 and the most recent significant eruptions occurred during a spate of activity from 1994 to 1995 which resulted in the further development of Gunung Barujari (G.Baru). Historical eruptions at Rinjani dating back to 1847 have been restricted to Barujari cone and the Rombongan dome (in 1944) and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake. The eruptive history of Rinjani prior to 1847 is not available as the island of Lombok is in a location that remained very remote to the record keeping of the era.
The 6 km by 8.5 km oval-shaped caldera is filled partially by the crater lake known as Segara Anak (‘Child of the Sea’) This lake is approximately 2000 metres above sea level and estimated at being around 200 metres deep; the caldera also contains hot springs. The Rinjani caldera forming eruption is thought to have occurred in the 13th century. Eruption rate, eruption sites, eruptiion type and magma composition have changed during the last 10,000 years before the caldera forming eruption. The eruptions of 1994 and 1995 have presented at Gunung Baru (or ‘New Mountain’ – approximately 2300 metres above sea level) in the center of this caldera and lava flows from subsequent eruptions have entered the lake. This cone has since been renamed Mount Barujari (or ‘New Finger Mountain’).
The highlands are forest clad and mostly undeveloped. The lowlands are highly cultivated. Rice, soybeans, coffee, tobacco, cotton, cinnamon, cacao, cloves, cassava, corn, coconuts, copra, bananas and vanilla are the major crops grown in the fertile soils of the island. The slopes are populated by the indigenous Sasak population. There are also some basic tourist related activities established on Rinjani primarily in or about the village of Senaru.
The volcano and the caldera are protected by the Gunung Rinjani National Park established in 1997. Tourism is increasingly popular with trekkers able to visit the rim, make their way into the caldera or even to make the more arduous climb to the highest point; fatalities, however, are not uncommon. In July 2009 the summit route was closed due to volcanic activity at that time and subsequently reopened when the activity decreased. During early 2010 up to and including May 2010 access to Rinjani was at times again restricted due to volcanic activity.
On 3 November 1994, a cold lahar (volcanic mudflow) from the summit area of Rinjani volcano traveled down the Kokok Jenggak River killing thirty people from the village of Aikmel who were caught by surprise when collecting water from the river in the path of the flow.
In connection with the eruption of the cone Gunung Barujari the status for Gunung Rinjani has been raised from Normal (VEI Level 1) to ‘be vigilant’ (VEI Level 2) since May 2, 2009 . In May 2010 Gunung Rinjani was placed in the standby status by Center for Volcanology & Geological Hazard Mitigation, Indonesia with a recommendation that there be no activity within a radius of 4 km from the eruption at Gunung Barujari.
source : wikipedia