Volcano

Avolcano is a mountain surrounding an 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 outside,forming a thin crust of cold, solid materials, containing hot liquid, magma, and gases. It was the very highpressure of the gases forcing the magma through weak parts in the earth’s crust that formed volcanoes.
There are some 500 volcanoes in Indonesia, of which about 180 are still active . They are found in three rows. The first row strtches over a distance of 7000 km fron North Sumatra – Java, the northern row af island of Nusa Tenggara ending up on the island on Saparua near Ambon.

The second row runs from Sulawesi thrugh Sangihe asa far as the Philipine island ; while the third runs from Irian to Halmahera, Kalimantan and the southern island 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 eruption the lava flows in every direction. The hot lava slowly cools off into what is called “ lahar”
In the rainy season , when the cool”lahaar” on Merapi’s slopes is hits 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 eruption 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, distance of 3’600 to 4,800 km from Krakatau. Around 18 cubic km of solid materials were thrown up. The skies above places were darkened. 30 meter high waves flooded the coasts of west Java and Lampung, sweeping away village 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, protect the soil against erosion, while the soil acts as a water reservoir giving water to the rivers.
Volcanic eruption may destroy life ,but they also make the land fertile.