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Volcano Assessment.

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Edward Phillips. February, 2002 Volcano Assessment The ground beneath our feet is constantly shifting ; as continents split apart and crunch together, new oceans open up and old ones are squeezed out of existence. The whole of the Earth's surface is forever breaking up and moving - very, very slowly, but with enormous force. The map of the world has been steadily changing for millions of years. About 500 million years ago, most of the southern continents were part of one landmass, called Gondwanaland. Very gradually, the landmasses drifted apart and came together again. About 175 million years ago, they formed a new continent called Pangaea and a new sea, called Tethys. The large landmass of Pangaea began to break up. Over the past 175 million years, very gradually, the continents have drifted apart to where they are now. Inside the Earth The Earth is made up of a number of layers. Like an apple, it has a skin, called the crust (or Lithosphere) which includes tectonic plates, a flesh called the mantle and a core, which is divided into the outer core of liquid metal (mainly nickel and iron)and the inner core of solid metal (mainly iron). The crust, which is made of solid rock has two parts - continental crust and oceanic crust. Beneath the crust is the mantle, made from a layer of hot melted rock called magma. CROSS -SECTION OF THE EARTH Tectonic Plates People often think of the Earth's surface as solid and stable, but it is always moving. A long time ago, people noticed that volcanic eruptions and earthquakes frequently occurred in the same place - often close to the sea. Volcanoes appeared on many early maps of the world, but it was not until the last century that an Irish engineer, Robert Mallet (1810 - 1881) drew up a detailed map that pinpointed where earthquakes occurred and this confirmed that they were concentrated in quite narrow zones - the same zones where most volcanoes are found. ...read more.


Helens, a volcanic peak in the Cascade Mountains of Washington State, USA. Mount Pinatubo After lying dormant for 600 years, Mount Pinatubo erupted suddenly in June 1991, spurting clouds of steam and ash 14,000 metres in the air. This showered an island 90 km away with so much grit and ash that the airport had to be closed. Huge clouds of ash were thrown into the air and blocked out the sun for days. The ash slowly settled and buried fields and villages for miles around. Over 100 metres of ash lay in drifts on the upper slopes of the volcano. Torrential rains followed, causing mud flows that cascaded down the river valleys and swept away roads, bridges and several villages. At least 400 people were killed and another 400,000 were left homeless. With no breathing masks to protect themselves from the gritty ash and fumes, many of the survivors developed pneumonia. Everyone suffered from badly inflamed eyes. PNEUMONOULTRAMICROSCOPICSILICOVOLCANOCONIOSIS is the name given to the effects of breathing the poisonous gases given off by volcanoes. Mount Erebus an active volcano in Antarctica: -- Mount St. Helens ON 18th May 1980, a huge explosion ripped Mount St, Helens apart, releasing clouds of ash and dust which are still in the atmosphere. Geologists knew that the volcano could erupt at any time. It had been dormant since 1857, but a series of small earthquakes during the 1970's suggested that magma was rising into the mountain. There were other warning signs too - the side of the mountain was bulging and steam and gas were escaping. At 8.32 a.m., an earthquake broke the bulging side loose, causing the worst landslide ever recorded. Rock and lava plummeted down the mountainside and clouds of hot gases and ash plunged the valley into darkness. The eruption killed 63 people, flattened forests and destroyed wildlife. The volcano continued to erupt violently for four days and there were smaller eruptions for several months. ...read more.


The new island was named Surtsey after Surt, the Nordic God of Fire. CAN VOLCANOES BE PREVENTED? We cannot stop volcanoes erupting and we cannot stop people from living near them and taking advantage of the fertile soils to grow their crops. Scientists try to give warnings about future eruptions so that people can be evacuated. They study movements in the rocks beneath the Earth's surface. Rising magma creates a series of tiny earthquakes which can be used as early warnings. The volcano shape can also be studied. As the magma chamber fills up, it begins to bulge or swell, which shows that the volcano is about to erupt. Even though we have this information, predicting eruptions is still dangerous and not always reliable, as we found out from the deaths of volcanologists Maurice and Katia Krafft at Mount Unzen in Japan in 1991. Laser beams are used to predict volcanic eruptions; a swelling of the volcano caused by a build up of magma can be detected by a change in the length of the laser beam. When Mount Etna erupted in 1983, dynamite was used to control the flow of lava and divert it into an inactive crater of the volcano. Planes have also been used to bomb lava flows to divert the course of the lava away from towns. Sources :- Eyewitness Science Guides - How the Earth Works - by John Farndon Dorling Kindersley Eyewitness Guides - EARTH - by Susanna Van Rose Dorling Kindersley Eyewitness Guides - VOLCANO - by Susanna Van Rose Volcanoes and Earthquakes - Ladybird Discovery series Horrible Histories - Disaster! The Story of Major Catastrophes. (Watts Books) Natural Disasters - Volcanoes (Watts Books) Collins Children's Encyclopedia The Children's Factfinder - Colour Library Direct Internet School sheets VOLCANIC PLUGS When the vent of a volcano is plugged by thick lava, it may explode- or die out altogether. If it dies out, the rest of the volcano may be slowly worn away to leave nothing but the hard plug. Sugar loaf mountain, in Rio de Janeiro is a plug, so is the Devil's Tower is Wyoming, USA. ...read more.

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