Sixty million years ago, tectonic movements in the earth’s crust resulted in uplifting of volcanic islands which are now known as the Indonesian archipelago. These islands, strung over five thousand kilometers of the equatorial seas, are a series of extinct and still active volcanoes. Vulcanologists have identified 500 volcanoes, of which 128 are still active.

One of the most impressive dormant volcanos is Indonesia’s second highest mountain, Gunung Rinjani in Lombok. It is located in center of the island and exhibits an impressive caldera with and east-west diameter of eight kilometers and a north-south axis of five kilometers. In the caldera basin is a beautiful crater lake and on the eastern edges rises towering Gunung Rinjani. Reaching at a height of 3,726 m, it is Indonesia’s highest mountain outside of Papua.

The huge, kidney-shaped crater lake, called Segara Anak, is located 200m down from the rim. Its high sulphur and mineral content gives it an eerie, artificial aqua hue. Across the lake are sheer cliffs 500m in height which drop dramatically in a sheer fall to the lake’s edge. On the eastern side, Gunung Bahru, a 415m high smoking volcanic cone, and a lava flow dating from the last eruption in 1900, jut ominously into the lake.

The two day ascent to the rim of the caldera is a lesson in bio-geography, as dramatic changes in terrain and vegetation occur with increasing altitude. Starting from the end of the asphalt road in village of Senaro, the footpath traverses open grassland devoid of any shade. Relief is keenly felt when the track enters a forest of towering teak and mahogany trees. Within its depths the air is damp and cool, with a micro-climate that supports a panoply of huge tree ferns, exotic fern species and proliferating multi-hued fungi. As the track begins to ascend, wild raspberry bushes abound.

During the second day of trekking the rain forest thins out and carpets of colourful moss and lichen cover boulders lining the path. The terrain morphs yet again to sheel where tufts of hardy grasses abound. Further along, pine trees attest to the cooler temperatures where an alpine flora flourish. The last effort to the caldera rim is arduous but ever so exhilarating as the trekker is rewarded with the magical vista of Segara Anak unfolding below.

A collaborative effort between the New Zealand government and the Indonesian Forestry Department have resulted in an award winning management program for the Rinjani National Park.