Explosive Power Most of the volcanic eruptions that occur are small and happen in volcanoes that are erupting gently most of the time However it is the other volcanoes people have to worry about the rare enormous volcanoes These explode violent blasts of ash gas and lava over nearby land and buildings melting villages in their path Volcano Action It is estimated that across the world at any time there are around 20 volcanoes erupting even right now as you read this sentence Most of these will be small ones that cause minor clouds of ash This ash can form a thin film of dust over cars and homes Most of these eruptions will be unnoticed partly because of their remote locations Every year there are a total of 50 to 70 volcanic eruptions Volcanologists the scientists who study volcanoes believe that there are more than 500 volcanoes around the globe that could go off at some point in the future Vast clouds of heavy hot stinging ash are erupting from a volcano somewhere on Earth right now 6
Studying Volcanoes Volcanologists sometimes need to get dangerously close to volcanoes to study them Volcanologists are interested in knowing more about volcanoes They study the processes involved in their formation and when how and why they erupt They study volcanic eruptions from the past and volcanoes that are erupting gently now They try to figure out what combination of factors collide to result in the biggest most disastrous eruptions Then they try to discover ways of getting better at predicting when a volcano is going to erupt If scientists can predict these eruptions they will be able to give people as much warning as possible so that they can move out of the path of destruction EARTH UNDER ATTACK Volcanologists make new discoveries about volcanoes all the time but it is still very difficult to predict exactly when a volcano will erupt until it is close to exploding Volcanoes are dangerously unpredictable Even volcanoes that have been peaceful for hundreds of years can one day spring to life again 7
CHAPTER 2 WHAT LIES BENEATH We live and move around Earth on solid ground Whether muddy soil sandy beach or mountain ledge all surfaces are on top of rock However we are actually floating on what lies beneath the solid rock Layer Upon Layer If you could travel from the surface deep into the center of Earth you would discover that our planet is made up of layers From surface to center the four major layers are the crust mantle outer core and inner core The crust is made up of hard rock that is between 4 and 50 miles 6 4 and 80 4 km deep in different places Some crust is land and some forms the floor of the oceans Around 3 billion years ago the outer part of our planet cracked and split into many pieces that fit together over the surface of the Earth a lot like the panels on a soccer ball These huge pieces of rock are called tectonic plates Tectonic Plates Earth's tectonic plates are constantly shifting but they do so incredibly slowly They float on the lower hottest parts of the mantle This part of the mantle is partly melted sticky rock The mantle is constantly changing because the rock in it can melt into liquid called magma Magma usually stays deep underground but sometimes it reaches the surface This usually happens at the weak points in the crust which are the gaps between plates Volcanoes are the places where magma escapes Juan de Fuca Plate North American Plate Eurasion Plate Pacific Plate Cocos Plate Caribbean plate Arabian Plate Indian Plate Philippine Sea Plate Pacific Plate African Plate Nazca Plate Australian Plate South American Plate Scotia Plate Antarctic Plate This map shows the major tectonic plates of our planet Plates meet at boundaries where volcanoes can occur
Red-hot magma cools to black rock at the Earth’s surface The outer part cools first but the inner part can stay hot for much longer EARTH UNDER ATTACK The intense heat of Earth’s core drives plate movements The inner core is the hottest part of the planet It is a ball of metal reaching 9,932 Fahrenheit 5,500 C This keeps the outer core as liquid rock The core heats up the mantle Magma constantly rises nearer the surface and sinks back toward the core as it cools creating a circular movement in the lower mantle It is this movement that drags the plates along 9
