This a short presentation about the geological phenomena we call volcanoes.
Long ago, it was the Romans who named it the mountain of fire.
So what is a volcano?
It is a large mountain with a crater at the top, inside of which there is a cauldron of heat created by liquid rock we call magma.
Think of it then as a portal to the inner crusts of the earth.
The whole thing exists on tectonic plates way down in the earth.
A volcanic eruption is caused when those tectonic plates collide and hot magma reaches the surface of the earth at the crater.
The magma now becomes lava and is spewed into the air.
Lava, hot ash, volcanic gasses and rock spew down the mountainside at lightning speed and at extreme temperature.
Many volcanoes are either dormant or extinct and some have never erupted at all.
Indonesia is a country in south east Asia and lies in the so called Ring of Fire.
There are many voclanoes in its vast archaepeligo of islands.
The most famous ones are probably Toba, Krakatao and Bromo.
Mount Toba erupted seventy thousand years ago and left a crater in the form of a huge lake 100 kilometres long, 50km wide and 500 metres deep.
Mount Toba is considered extinct.
Krakatoa is different. It lies in the sea in the Sunda Strait between the islands of Sumatra and Java.
Krakatoa was a dormant (sleeping) volcano until it suddenly erupted in 1883 and killed many hundreds of thousands of people.
Kratatoa is an example of a volcano which lies under the sea and causes tsunamis.
The original Krakatoa is now extinct but amazingly a new volcano emerged in its place which is called today The Child of Krakatoa.
Mount Arenal in Costa Rica is another more recent example of a dormant volcano having a sudden eruption in 1968 and leading to a loss of human life.
Mount Bromo, on the other hand in east Java, remains active to this day and is a great attraction on the Indonesian tourist trail.
Visit with care!
Volcanolgists talk a lot about Supervolcanoes, of which Mount Toba was one. Yellowstone is one in the United States which is being watched closely while the last supervolcano to erupt was Mount Helena, also in the United States, in 1980.
Volcanoes are obviously extemely dangerous to life of any kind living within say a specific radius but this does not deter some people from accepting the risks and living on the mountain slopes of a volcano.
Volcanic soil is rich in potassium and phosphorus, providing nutritients to fertile farmland and producing geothermal heat energy to warm water and run power plants.
There are about fifteen hundred volcanoes on planet earth today
The sight of an erupting volcano is certainly a spectacular sight but best of course seen at a safe distance and taking all necessary precautions.
That is the end of my presentation about Volcanoes.
Thank you for listening.