krakatau tour

Contrary to the 1969 Hollywood film Krakatoa, East of Java, the remains of the island of Krakatoa lie to the west of Java, in the Sunda Straits, Indonesia. Indonesia is famed for its number of volcanoes – over 130 in all. These beautiful islands are part of a great volcanic belt which circles the Pacific Ocean, from New Zealand through Indonesia, northward to the Philippines and Japan, across the Aleutian Islands in Alaska, then southward along the western seaboard of North and South America. The belt forms the notorious 'Pacific Ring of Fire', a region of Earth that has spawned many volcanoes of extreme violence.

Ring of fire

A geological map will show that volcanoes typically occur in long belts similar to the Pacific Ring of Fire. The reason lies within Earth's crust. The crust of our planet is not a perfect and unbroken spherical shell. It's composed of eight separate major 'tectonic plates' which jostle each other around the globe, driven by heat from within Earth. At the 'plate boundaries' where the plates meet, the crust is typically being torn apart or is sinking. Both of these plate boundary processes result in the production of magma (molten rock). An active volcano must have a source of magma which eventually escapes and erupts at the surface. Hence the formation of volcanic belts that lie along plate boundaries.

The volcanoes of the Pacific Ring of Fire, including the island of Krakatoa, exist because deep beneath them two plates meet and the crust of one is sinking below the other. As the crust sinks into Earth's interior it heats and melts, forming magma. Similar to a lava lamp, the hot magma rises until it stalls just below the surface. Over time, pressures in a magma chamber can build phenomenally. If the overlying crust is unable to contain the pressure, a volcanic eruption occurs spewing out huge quantities of magma, fractured rock and ash.

The great eruption

Volcanoes have Jekyll and Hyde personalities. They can lie dormant for hundreds or even thousands of years before springing into life with little warning. Krakatoa's awakening occurred on 20 May 1883 with a series of powerful earthquakes and explosions that were heard over 150 kilometres away. In the days that followed, an ominous black cloud of ash rose over 10 kilometres high and gently fell on neighbouring islands. Unbeknownst to those who inhabited the nearby islands, this was just the prelude to the most fearsome eruption in recent history.

Krakatoa continued to rumble and belch harmlessly for three months; so much so that most Indonesians grew complacent to the volcano's stirrings. That was until the events of two fateful days, Sunday 26 and Monday 27 August.

A little after lunchtime on the Sunday, great explosions began at 10-minute intervals. They steadily grew louder. By 5pm enormous booms were heard all over Java. In Batavia (now Jakarta), 160 kilometres from Krakatoa, the din was compared to close range artillery shells exploding, with shockwaves that rattled windows and shook chandeliers.

As darkness fell on the Sunday, the volcano's huge eruption column lit up like a Christmas tree. Tremendous turbulence in the air caused violent discharges of static electricity, forming brilliant, almost continuous flashes of lightning. Krakatoa's crescendo was about to follow. On the morning of the Monday, an almighty eruption blew a column of ash 80 kilometres high, to the very edge of space. Hot rocks the size of pumpkins rained down around the Sunda Straits, hundreds of kilometres from the volcano. Ash fell as far as the Cocos Islands, 1850 kilometres away. The loudest explosions were so phenomenal that they woke people in south Australia 3224 kilometres away and were heard 4000 kilometres away.