Mount Rinjani or gunung rinjani is an active volcano in Indonesia on the island of Lombok.
Administratively the mountain is in regency of east Lombok, west nusa tenggara ( Indonesian: nusa tenggara barat, NTB). It rises to 3,726 meters (12,224 ft), making in the second higest volcano in lndonesia.
On the top of the volcano is a 6-by-8.5- kilometer (3.7 by 5.3 mil) caldera, which is filled partially by the crater lake known as segara anak or anak laut (child of the sea) due to blue colour of water lake as laut (sea).
Segara anak lake is crater lake contained within mount rinjani on the island of Lombok in indonesia. The name segara anak means child of the sea given to the blue colour of the lake reminiscent of the sea. The lake is heated, so its temperature is 20-22 OC, about 5-7oC above the expected temperature for a lake in that altitude. At the west end of the lake is the volcanic cone gunung baru (new mount), giving to the lake recent shape. Gas bubbles escape from the lake floor. The lake ph is 7-8.
This lake approximately 2,00 metres (6,600ft) above sea level and estimated to the about 200 metres (660 ft) deep;the caldera also contain hot spring sasak hindu people assume the lake and the mount are sacred and some religion activities are occasionally done in the two areas.
A massive eruption of rinjani in 1257 CE may have triggreted an episode of global cooling and failed harvests.