While Indonesia’s volcanoes are often noted for the beauty of their spectacular peaks, steaming craters and view of the earth’s bubbling core, Mount Merapi, the country’s most active volcano, took centre stage this past October as a clear reminder of their deadly activity. Many of Indonesia’s volcanoes do erupt, sometimes with shocking consequences.
Due to Indonesia's placement on a significant segment of the Pacific "Ring of Fire", two large crustal plates (the Indian Ocean and western Pacific) are forced under the massive Eurasian plate, where they melt, approximately 100km beneath the surface. Some of the magma rises and erupts, forming the string of volcanic islands across Indonesia.
But with tectonic activity comes devastating earthquakes and tsunamis, such as those of Boxing Day 2004, off Java in July 2006 and Sumatra in 2009, and just recently around the surfer's paradise of the Mentawai Islands. Here is the lowdown on Indonesia's most beautiful, and its most volatile, volcanic monsters.
Volcano peaks, part of the huge Tengger Massif in Java
Gunung Bromo, Java
A landscape of epic proportions and surreal beauty, Gunung Bromo is one of Indonesia's most breathtaking sights. Surrounded by the desolate Sea of Sands, its peak is sacred and eerie. It may not be Java's tallest volcano, but it is easily its most magnificent. From the summit you can see two other volcanoes (one in various stages of activity), all set in the vast caldera of yet another volcano.
Compared with Java's other major peaks, Gunung Bromo is a midget. But this volcano's beauty is in its setting, not its size. Rising from the guts of the ancient Tengger caldera, Bromo is one of three volcanoes to have emerged from a vast crater that stretches 10km across. Flanked by the peaks of Kursi and Batok, the steaming cone of Bromo stands in a sea of ashen, volcanic sand, surrounded by the towering cliffs of the crater's edge. Nearby, Gunung Semeru, Java's highest peak and one of its most active volcanoes, throws its shadow - and occasionally its ash - over the whole scene.
Gunung Semeru, Java
Part of the huge Tengger Massif, the classic cone of Gunung Semeru is the highest peak in Java, at 3,676m. Also known as Mahameru (Great Mountain), it is looked on by Hindus as the most sacred mountain of all and the father of Gunung Agung on Bali. Semeru is one of Java's most active peaks and has been in a near-constant state of eruption since 1818. In 1981, 250 people were killed during one of its worst eruptions, and it exploded as recently as March 2009.
Gunung Krakatau, Java
Take a boat trip to see the remnants, and the new beginnings, of one of the world's A-list volcanoes. Few volcanoes have as explosive a place in history as Krakatau, the island that blew itself apart in 1883. Turning day into night and hurling devastating tsunamis against the shores of Java and Sumatra, Krakatau quickly became vulcanology's A-list celebrity. Few would have guessed that Krakatau would have snuffed itself out with such a devastating swan song. Krakatau may have blown itself to smithereens, but it is currently being replaced by Anak Krakatau, which has been on the ascendant ever since its first appearance nearly 80 years ago. It has a restless and uncertain temperament, sending out showers of glowing rocks and belching smoke and ashes.
Gunung Agung, Bali
Take one of the numerous routes up and down Bali's tallest and most sacred mountain. Gunung Agung is an imposing peak seen from most of South and East Bali, although it is often obscured by cloud and mist. Many references give its height as 3,142m, but some say it lost its top in the 1963 eruption and opinion varies as to the real height. The summit is an oval crater, about 700m across, with its highest point on the western edge above Besakih.
Kawah Ijen, Java
Spend the night at a peaceful coffee plantation before climbing this volcano to view its remarkable turquoise sulphur lake. The fabled Ijen Plateau is a vast volcanic region dominated by the three cones of Ijen, Merapi and Raung. A beautiful and thickly forested alpine area, these thinly populated highlands harbour coffee plantations and a few isolated settlements - Gunung Ijen is Javanese for "Lonely Mountain". Access roads to the plateau are poor, and perhaps because of this visitor numbers are low. Virtually everyone that does come is here for the hike up to the spectacular crater lake of Kawah Ijen. But with sweeping vistas and a temperate climate, the plateau could make a great base for a few days up in the clouds away from the crowds.
Kelimutu, Nusa Tenggara
Wonder at the ethereal scenery atop this volcano, with its three differently coloured crater lakes and lunar landscape. There are not many better ways to wake up than to sip ginger coffee as the sun crests Kelimutu's western rim, filtering mist into the sky and revealing three deep, volcanic lakes - each one a different striking shade. That is why the tri-coloured lakes of Kelimutu National Park have long been considered a Nusa Tenggara must. During our research one was turquoise, the other dark brown with flecks of rust and the third was black glass. Colours are so dense that the lakes seem the thickness of paint.
Gunung Rinjani, Lombok
Join pilgrims at the summit of this sacred peak, which has a huge crater lake overlooked by the active cone of Gunung Baru. To the Balinese, who come once a year, Rinjani is one of three sacred mountains, along with Bali's Agung and Java's Bromo. Inside the immense caldera, 600m below the rim, is a stunning, 6km-wide cobalt-blue lake, Danau Segara Anak (Child of the Sea). The Balinese toss their jewellery into the lake in a ceremony called pekelan, before they continue toward the sacred summit.
Gunung Kerinci, Sumatra
Brave this challenging ascent up into the heavens on Sumatra's highest peak. Dominating the northern end of the park is the 3,805m Gunung Kerinci, one of Sumatra's most active volcanoes (it last erupted in 2009) and Indonesia's highest non-Papuan peak. On clear days the summit offers fantastic views of Danau Gunung Tujuh and the surrounding valleys and mountains.
Gunung Api, Maluku
Scramble up this volcano in the Banda Islands to experience the awesome sunrise views. This devilish little 666m volcano has always been a threat to Bandaneira, Lonthoir and anyone attempting to farm its fertile slopes. Its most recent eruption in 1988 killed three people, destroyed more than 300 houses and filled the sky with ash for days. Historically, Gunung Api's eruptions have often proved to be spookily accurate omens of approaching intruders.