Bali And Lombok lie in one of the geologically most active regions on earth, part of the Pacific Rim’s great “ring of fire”. They are two in a chain of volcanic islands which stretches some 3,500 km (2,200 miles) from Sumatra to Flores, and which marks the point where the Australian tectonic plate is being forced beneath the Eurasian plate at a rate of 6 cm (2 inches) each year. The volcanoes of Bali and Lombok have influenced the way human societies on the islands have developed, and still play a very important role in the culture of the islands’ inhabitants.
The peak of Gunung Batur, seen here from the air, and nearby Lake Batur are set in a spectacular caldera, created about a million years ago, when the top of the mountain was explosively blown off by the pressure of accumulated magma.
Deep gorges and steep ridges run north and south from the higher peaks, making east-west travel difficult.
This is why traditional Balinese society developed along river valleys and on the coastal plains.
Lake Tamblingan lies in an ancient caldera. Volcanoes, such as Gunung Lesong, have grown within the caldera since its formation, hiding all traces of the southern rim.
Volcanic activity, including the deposition of magma, can cause changes in the landscape. These drawings show the rapid changes in the peaks of Gunung Batur during the major eruption of 1926. Today the volcano is still active and it enjoys small, regular eruptions.
The last one in 2000 created a small cone, which is visible from Kintamani. Other major eruptions in recent years include that of Gunung Rinjani in 1994 and that of Gunung Agung in 1963. The latter caused widespread devastation and hardship.
THE VOLCANIC LANDSCAPE
The line of volcanic peaks running along Bali and Lombok is the islands’ most conspicuous physical feature.
One mountain or another is visible from almost any location. The combination of volcanic soil and rainfall has created a richly fertile environment for agriculture.
Gunung Rinjani, at 3,726 m (12,224 ft), is Indonesia’s second-highest mountain. Within its caldera is the small but still active volcano Gunung Baru, and a beautiful crater lake, Danau Segara Anak.
The south coast of Nusa Penida was formed from ancient coral reefs raised above the surface of the sea, as a result of volcanic activity.
Fertile rice fields are irrigated by the streams flowing down Gunung Rinjani. The soil is rich in tephrites and silica.