The Fame of Gunung Merapi: Central Java, Indonesia

Gunung Merapi, although highly active at the moment, has always stood ominously over the city of Yogyakarta. The mountain and I have been friends for well over a decade and it always seems to smile at you from wherever you are standing in the city.

I have many friends that live near the mountain and some that are in the lava's path should it erupt violently. Over the years I have climbed it, admired it, walked around it many times but always respected the majestic monster.

The other day I was reading an article by well known journalist Sri Wahyuni and in this explains how Gunung Merapi is internationally renowned and not just because of the pending eruption or in connection with the recent devastating earthquake that occurred in Yogyakarta.

If and when the mountain decides to quieten down and if you are in Yogyakarta, then do yourself a favour and take a hike up to the caldera or as close as you can get by foot. Enjoy its majesty, the natural beauty upon its slopes and especially the characters who make a living on the mountain.

Merapi: A volcano of international renown
Sri Wahyuni, Yogyakarta

When it comes to eruptions Mt. Merapi is a one of a kind. Now 100 meters higher than it was before this year's eruption began, Mt. Merapi's style is unique - in fact these days there are other volcanoes around the world described as having a "Merapi Eruption".

"In this world there are at least two other volcanoes that are known as having the same type of eruption as Merapi" said volcanologist Antonius Ratdomopurbo who heads the Yogyakarta Volcanology Office.

Merapi, which stood at 2,968 meters before this year's eruption does not explode vertically sending hot lava and gas in all directions when it erupts.

"Merapi rarely explodes that way" said Ratdomopurbo, or Purbo as he is popularly called, who has been monitoring the volcano for over 20 years.

An eruption at Mt. Merapi said Purbo is always proceeded by the formation of a new lava dome, the consequence of increased volcanic activity producing massive amounts of lava. A lava dome is a pile of magma that comes to the surface and forms a dome-like shape on the peak of the volcano.

When it forms at the center of the volcano's summit, it has an even shape and from a distance looks like half an upside-down coconut shell.

If it forms on the edge however it is not so pretty and often will directly flow down the slope turning into flaming hot lava, and in larger volumes, deadly hot clouds.

Locals call these hot clouds wedhus gembel &$40;sheep in Javanese) as they resemble the fluffy wool of a sheep.

As the magma supply to the dome grows in volume so to will the dome grow. At such a time the new lava dome is not stable and could collapse at any time sending down huge super-high temperature clouds up to 12 kilometers down the side of the mountain burning everything in their path.

Pulling along with them giant stones, sand, ash and hot gas, the temperature of the clouds is between 800 and 1,000 degrees Celsius at the dome and can still be as high as 400 degrees when they reach inhabited areas.

The hot clouds of this years' eruption are estimated to be over 500 degrees and are travelling down Merapi's slopes at speeds of up to 200 kilometers per hour.

"The collapse of the new lava dome is Merapi's biggest threat. It is the peak of the eruption process and its usually understood by the public to be the explosion of Merapi" Purbo said.

The collapse could be made worse if it brings down with it one or more lava domes left by previous eruptions. This is quite possible as the collapse of a new lava dome usually affects the stability of older ones.

Sometimes a lava dome collapse occurs because of a vertical explosion although this is rare at Mt. Merapi. During the 1997 eruption a relatively small scale vertical eruption caused old domes to become unstable and collapse down the slopes of the mountains creating huge hot clouds.

A new lava dome does not always collapse, although this is quite rare, said Purbo, and sooner or later domes were usually destroyed through eruptions.

Merapi is a very active volcano with a resting period of between only two and seven years. Each eruption however is unique in that they time needed by the volcano to reach the eruption peak and the collapse of the new lava dome, is different each time.

"Sometimes it collapses only within days after expelling the first hot cloud. Other times it needs months to collapse" says Purbo.

In 1994 the formation of the new lava dome started in March and became more and more intense in August as it started spewing massive hot clouds. Then it cooled down during September and October and suddenly collapsed on Nov. 22.

The new lava dome of the 2006 eruption was first seen in February and got bigger and bigger both in volume and form over the following months. It was declared to be on its highest alert status on May 13.

It showed a decline in intensity after around one of third of the 4.3 million cubic meters of lava in the newly formed dome collapsed on June 9 causing the volcanology office to downgrade the alert status to the second highest level on June 13.

Then, all of a sudden on June 14 it sent out huge hot clouds, the biggest ever of this year's eruption killing two volunteers trapped in a bunker in the Kaliadem tourist resort in Cangkringan, Sleman.

"Merapi is indeed unpredictable. We cannot provide a precise prediction on for example whether the newly formed lava dome will collapse" said Purbo.

What is more important however, according to Purbo, is how to deal with all the possibilities.

By learning the characteristics of every single eruption of Merapi, he said, Merapi can be better understood. It is through such eruptions that Merapi reveals itself to people.

"We all are supposed to better understand Merapi each time it erupts" he says adding that doing so will make it possible for the people to avoid becoming a casualty of Merapi.