page_title: Mount Rinjani
section_title: Volcanic composition
hierarchical_section_title: Mount Rinjani / Volcanology / Volcanic composition
caption_attribution_description: English: This panorama of Mount Rinjani and its summit, crater, and ash cone, was taken from an altitude of about 2,600 meters.
context_page_description: Mount 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. It rises to 3,726 metres, making it the second highest volcano in Indonesia.
  Adjacent to the volcano is a 6-by-8.5-kilometre caldera, which is filled partially by the crater lake known as Segara Anak or Anak Laut, due to the color of its water, as blue as the sea. This lake is approximately 2,000 metres above sea level and estimated to be about 200 metres deep; the caldera also contains hot springs. Sasak tribe and Hindu people assume the lake and the mount are sacred and some religious activities are occasionally done in the two areas. UNESCO has made Mount Rinjani Caldera a part of the Global Geoparks Network in April 2018.
context_section_description: In Lombok, Rinjani volcano lies approximately 300 kilometres (190 mi) north of the Sunda Trench (also known as Java trench) and is situated about 170 kilometres (110 mi) above the active north dipping Benioff zone. Based on the composition of andesites which have very low Ni concentrations and low Mg/Mg+Fe It is suggested that the Rinjani suite is of mantle origin, but that all the andesites and dacites as well as many of the basalts have probably been modified by fractional crystallization processes. It is concluded that the Rinjani calc-alkaline suite, which in many respects is typical of many suites erupted by circum-pacific volcanoes, probably originated by partial melting of the peridotite mantle-wedge overlying the active Benioff Zone beneath Lombok Island. The Pleistocene-Recent calcalkaline suite from the active volcano, Rinjani is composed of a diverse range of lavas. These include: ankaramite, high-Al basalt, andesite, high-K andesite and dacite. Sr-isotopic and geochemical constraints suggest that this suite was derived from the sub-arc mantle. Geochemical models suggest that fractional crystallization is an important process in the suite's differentiation, although the series: ankaramite-high-Al basalt-andesite-dacite does not represent a continuously evolving spectrum of liquids.
  In September 1995 an aviation report was issued concerning an unconfirmed ash cloud from Rinjani. A NOTAM about volcanic activity from Rinjani was issued by the Bali Flight Information Region on the morning of 12 September. An ash cloud was reportedly drifting to the south west with the cloud top around 4 km (2.5 mi) altitude.
  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. One person remained missing as of 9 November 1994. No damage to the village was reported. Local volcanologists noted that additional 
  lahars could be triggered by heavy rainfall.
  During 4 June 1994 – January 1995 the DVGHM (Directorate of Volcanology and Geological Hazard Mitigation) noted that explosions occurred on Rinjani.  Those explosions came from the Barujari volcano.
  Between 3 June 1994 and 21 November 1994 records of Rinjani's eruptive history indicate activity accorded Volcanic Explosivity Index (VEI) with a rating of 3(?) with the area of activity described as Gunung Barujari. Eruptive characteristics documented for the events of that time are described as, central vent eruption with an explosive eruption, with pyroclastic flow(s), lava flow(s), fatalities and mudflow(s) (lahars).
  In May 1994 a glow was noticed on the crater floor of Barujari cone, which at this time had undergone no significant activity since August 1966. A portable seismograph (PS-2) and telemetry seismograph (Teledyne) were put into operation on 27 May and 9 June, respectively. One volcanic earthquake event/day was recorded on 27, 28, 30, and 31 May. After 4 June, however, volcanic tremor with a maximum amplitude of 35 mm was recorded, presumably associated with the upward movement of magma.
  At 0200 on 3 June1994, Barujari cone began erupting by sending an ash plume 500 m (1,600 ft) high. One 8 June 1994 press report described emission of "smoldering lava" and "thick smoke," as well as ashfall in nearby villages from an ash cloud rising 1,500 m (4,900 ft) above the summit. Between 3 and 10 June 1994, up to 172 explosions could be heard each day from the Sembalun Lawang volcano observatory (about 15 km (9.3 mi) NE). During this period, seismic data indicated a dramatic increase in the number of explosions per day, from 68 to 18,720. Eruptions were continuous at least through 19 June 1994, with maximum ash plume heights of 2,000 m (6,600 ft) on 9–11 June 1994.
  Between 28 March 1966 and 8 August 1966 records of Rinjani's eruptive history indicate activity accorded a Volcanic Explosivity Index (VEI) rating of 1.
  Lava volume of 6.6 million cubic metres (230×10⁶ cu ft) an
caption: The summit, ash cone, and lake are all visible from this vantage point at 2,600m on the eastern ridge.
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