The first historically documented eruption of Mount Batur was in 1804, and it has been frequently active since then. The worst eruption was in 1917, when a violent eruption killed thousands of people and destroyed more than 60,000 homes, 2,000 temples and old people might tell you this was “the year when the world shook”. Other eruptions have taken place since and forcing the local population to be relocated, along with several of their temples including one of the main Bali temples, Pura Ulun Danu Batur. Initially was located on the foot of Mount Batur inside the huge crater, this temple has been relocated to the top of the summit ridge and now offers an impressive overlooking of Mount Batur. The last small erupted was in 2000.
For Bromo residents, Tengger tribe, Mount Brahma (Bromo), believed to be a sacred mountain. Once a year the community held “Yadnya Kasada or Kasodo” ceremony. The ceremony was held at a temple which is under the foot of Mount Bromo and proceed north to the top of Mount Bromo. The ceremony was held at midnight to early morning every full moon around 14 or 15 in Kasodo (tenth) according to the Javanese calendar.
Mount I j e n
Located in Banyuwangi, East Java, Ijen consists of several small
stratovolcanoes and a 20km wide caldera. The highest point is Mount
Merapi. To the west lies Ijen Mount and its famous lake souring 9000ft
above sea level. Ijen Lake is the largest caldera lake in Java Island
and also the most acidic in the world with the acidity level close to
0.2, which is enough to dissolve human flesh. The size of the crater is
about 960m x 600 m with 200m depth. Ijen is an active volcano. The first
eruption occurred around 640 BC. Many small eruptions occurred
afterward. In 2004, the lake changed color from green to white releasing
sulfurous rocks and foam in the process. Due to this increased
activity, the area was temporarily closed for visitors. On 29th July
2002 small explosion occurred. Ash emission lasted until mid August. On
15th July 2000 sulfur emission from the volcano entered the cabin of a
Singapore-Denpasar flight. Another small explosion occurred in 1999,
1994 and 1993, and a bigger one in 1952.
The mountain is located in the middle of Ijen National Park. Besides its dramatic volcano scenery, Ijen National Park also offers collections of animals such as Javanese porcupine (hystrix brachyuran javanica), and other species of rare trees and flowers commonly grow in tropical rain forest. In August to September, beautiful edelweiss blooms everywhere in the mountain. Green coffee plantations are variously scattered on the floor of the caldera.
You could also take a day tour around the caldera. On Ijen lakeshore there are thermal springs. The discharges have magmatic and hydrothermal component. It may be helpful to wear mask or handkerchief to protect yourself from sulfuric fumes. Ijen provides not only interesting panorama for tourist but also a fascinating subject for geologist or for those who are interested in geochemical phenomena.