Volcanoes

Without doubt, erupting volcanoes are one of the most awesome and terrifying sites in nature. It’s estimated that one in ten of the world’s population live within “danger range” of volcanoes. There are 1511 ‘active’ volcanoes across the globe, and many more dormant ones that could recharge at any moment.

How do volcanoes happen?

Volcanoes begin deep in the earth. Right inside the liquid core it is hotter than fire. Outside the core is the mantle. This is more solid, but still very hot. Around the mantle is the Earth’s crust, with land and sea on top.





When a volcano erupts, it gets rid of heat from deep inside the Earth. In the mantle and crust, rocks melt down intomagma. The magma is under pressure so it gradually rises, often up cracks, and blasts its way to the surface. At this stage, the volcano belches out gases, dust and fragments of rock. Lava that piles up around the opening (vent) forms a typical cone-shaped mountain.




Where volcanoes happen?

Like earthquakes, volcanoes form at weak points in the Earth’s crust, known as ‘fault-lines’. The Earth’s is made of huge segments of rock called plates. When two plates collide, one section slides on top of the other, the one beneath is pushed down into the mantle. Magma is squeezed up between two plates. Then a volcano forms.



Over half of the world’s volcanoes arise in a belt around the Pacific Ocean called the Ring of Fire.

Some volcanoes are not found near plate edges. They are made when magma comes up through hot spots where the crust is thinner.

Volcano shapes

Some volcanoes are flat. They are made of layers of liquid ash. These are called Shield volcanoes. They are built up and have broad, gently sloping sides.





Other volcanoes are steep-sided. They are made of ash and lava and are built up in layers. The sides of the volcano are very steep. These are called Strato volcanoes.





Some are very small cone-shaped volcanoes and are called Cinder cones. That is because they are built of erupting lava that breaks into small pieces as it shoots into the air. As they fall back to the ground, they cool and form cinders around the vent.



When do volcanoes happen?

Some volcanoes give warning signs before they explode. Smoke comes from the top and nearby ground trembles. But some volcanoes stay quiet and blow up very suddenly. Sometimes hot water is pumped to the surface by digging wells.

People who study volcanoes are called Vulcanologists.. They try to predict when a volcano will erupt. This is very difficult especially if a volcano has been dormant for centuries. But there are clues. Tiltmeters on a volcano’s side record changes in the mountain’s slope, suggesting activity inside. Or the volcano might begin to give of more ash and gas.






Studying volcanoes is dangerous work, even with protective clothing. The metal coating of the suit reflects the heat of an eruption, keeping the wearer cool.

Volcanoes - helpful or harmful?

Volcanoes are dangerous but they can be very useful. The hot magma below a volcano can heat up underground water. It comes out of the ground as a hot spring.

In Japan people bathe in hot springs. In some countries people use the hot water for cooking.

Volcanoes also help farmers because lava makes a rich soil. It contains many minerals that help plants to grow. People grow crops in lava in India, Italy and the Canary Islands.



Volcanic Eruptions 

In August 1883 a huge explosion happened in Krakatoa in Indonesia. This volcanic island blew itself in half. Then huge waves followed and they swept away 36 000 people on other islands. When Krakatoa exploded, it sent shock waves around the world. Smoke and dust from the burning volcano made bright sunsets in the sky.

A famous volcano disaster happened in Italy, a long time ago. In AD 79 Mount Vesuvius exploded and hot ash buried the city of Pompeii. It killed 20 000 people.

In Japan there is a volcano called Mount Unzen. In 1792 it erupted and killed 15 000 people. On 3 June 1991, Mount Unzen blew up again. Floods of lava ruined many homes but luckily most people survived.

Another volcano erupted in June 1991. Mount Pinatubo in the Philippines had been sleeping for 600 years. Then in 1991 it suddenly roared loudly and a huge cloud of ash rose into the sky. The ash spread over Singapore, Malaysia and Vietnam.