VOLCANOES

A volcano is a mountain surrounding an opening in the earth’s crust. Steam, gases, lava, ashes and other materials are forced out almost continuously from an active volcano. A dormant volcano, on the other hand, erupts at long intervals. In an extinct volcano, the crater has long been closed up with cold, solid lava.
Our earth was a sphere of gases which slowly cooled off from the outside, forming a thin crust of cold, solid materials, containing hot liquid, magma, and gases. It was the very high pressure of the gases forcing the magma through weak parts in the earth’s crust that formed volcanoes.
There are some 500 volcanoes in our country, of which about 180 are still active. They are found in three rows. The first row stretches over a distance of 7,000 km from North Sumatra Java, the northern row of islands of Nusa Tenggara, lying outside those rows, are not volcanic.
Most of our volcanoes are in Java. The most active one is Mount Merapi at the north of Yogya. The northern part of the crater has a high wall, so in eruptions the lava flows in every direction. The hot lava slowly cools off into what is called “lahar”.
In the rainy seaso, when the cool “lahar” on Merapi’s slopes in hit by rain it flows down the slopes with great force, destroying everything in its path. The flow of “lahar” mixed with rocks fills up the rivers, while sand covers the fields.
The eruptions of sea volcanoes cause high waves, flooding regions on the coasts. This happened when Krakatau erupted in 1833.The sound of the eruption was heard from places as far away as India, Irian, and Australia, distances of 3,600 to 4,800 km from Krakatau. Around 18 cubic km of solid materials were thrown up. The skies above places as far away as the Southern Pacific, Africa, and South America were darkened. 30 metre high waves flooded the coasts of west Java and Lampung, sweeping away villages and 35,000 people.
However, volcanoes are also a great blessing. Volcanoes and mountains force the clouds to rise, and cool them off, causing them to drop the water they contain in the form of rain. The materials thrown up by volcanoes contain minerals needed by plants. The higher regions, being cool, are good for coffee, tea and other plantations. The woods on the slopes protect the soil against erosion, while the soil acts as a water reservoir giving water to the river.
Volcanic eruptions may destroy life, but they also make the land fertile.