Sunday, April 8, 2007

Active volcanoes

The Philippines is an archipelago of more than 7100 islands. Most of these islands are of volcanic origin.

There are 37 volcanoes in the Philippines, of which 18 are still active volcanoes. It means that an eruption occurred in the last decennia and that a new eruption can be expected in the future. All the other volcanoes are 'sleeping' or 'dead' volcanoes. Scientists think that an eruption of these volcanoes is unlikely. The most known volcanoes in the Philippines are Mount Pinatubo, Mount Mayon and the Taal volcano. They are all located on the Northern island Luzon.

The most active volcano

Mount Mayon is the most active volcano in the Philippines. Since 1616 there were 47 eruptions.

From 1616 until 2002 at least 1300 people died and thousands of people got homeless as a result of all the eruptions. The most recent eruptions were in 1947, 1984 and 1993. In 1993 the activity started with explosions. Half an hour later, flows of lava (molten rock) and pyroclastic flows (flows with mixtures of hot, dry rock fragments and hot gases.

They flows may result from the explosive eruption of molten or solid rock fragments, or both) came out of the crater in the top of the volcano. It killed 68 people and 60.000 people had to be evacuated.

Volcano type

Mount Mayon is a splendid example of a strato volcano. Mount Mayon rises up 2462 meters above sea level.

This type of volcano is typically steep-sided and composed of alternating layers of lava (the melted mass - magma - which came out of the crater) and other volcanic material, especially ash layers.

The lost village of Cagsawa

In 1818 enormous flows of lava came over the village of Cagsawa. The whole village disappeared under the layers of 'lava' and 'pyroclastic flows'. Only the the top of the church reminds of the period that once there was a village.

Climbing Mount Mayon?

For some sportive tourists it is a challenge to climb the Mount Mayon. The best start is at a height of 762 meters above sea level, the location where a research- station is situated. From the research station a trail creeps upwards through a tropical secondary forest. It is not easy to reach the summit. Especially the last 540 meters to the top. At the height of 1921 meters the rocky slopes begin. The last 240 meters have a 40 degree ascent on loose volcanic cinder and lava sands. To climb further to the summit is not without danger for life. Especially the danger of poisonous fumes, which can sometimes come down alongside the slopes when the wind makes a sudden shift in wind direction. So, the best, safe trail just stops at 1921 meters altitude!

Mount Pinatubo

Mount Pinatubo is situated in the southern part of Luzon. It is one of the biggest volcanoes in the Philippines. In 1991, the Pinatubo became in a few months one of the most known volcanoes in the world. In that year the Pinatubo erupted violently.

The summit of the volcano collapsed!

The violent explosion on the 15th of June in 1991 broke away a big part of the top of the Pinatubo*. The summit of the volcano collapsed into the under laying magma chamber. The result was an enormous depression, the caldera, with a 2.5 kilometre diameter!
The new summit of the volcano was 145 meters lower than before the explosion.
More than 700 people were killed. Huge masses of volcanic material** flew out of the crater and covered in a few days an area of more than 400 km². At the beginning of the eruption enormous ash clouds*** were blasted out into the air.

The eruption in 1991

At first there were earthquakes, small explosions and emissions of steam and minor ash. The earthquakes and emissions continued and increased. After more than 2 months of increasing activity, strong explosions culminated in one of the largest eruptions of this century. During more than 15 hours, volcanic ash plumes went straight up to 30 km altitude into the sky. The ash plumes spread out in the air in the days after the first explosions. Within ten days, the cloud formed a nearly continuous band that stretched 11.000 kilometres from Southeast Asia to Central Africa!