4 EARTHLY EXPLOSIONS Imagine you’re looking at a mountain From the outside it is big solid and steady Suddenly great bursts of fire shoot into the air Clouds of ash and gas roar into the sky Rivers of lava race down the sides Now it is clear that is a volcano not a mountain Volcanoes have fasci nated people for centuries The ancient Romans believed volcanoes erupted Fiery lava explodes from the mouth of a volcano Volcanic eruptions are both dangerous and fascinating
5 when their god of fire Vulcan made thunder bolts and weapons Other cultures explained volcanoes as outbursts of anger from a god or goddess These beliefs were a way to understand something that seemed mysterious Today scientists can explain a great deal about volcanic activity However it still seems mysterious Volcanic activity brews underground beneath our feet and we cannot see it until a great explosion forces us to look The word volcano comes from the name Vulcan who was the Roman god of fire Why do you think volcanoes were named after him THINK ABOUT IT Vulcan was also the god of metalworking Here he forges a weapon with fire and tools
6 A volcano is an opening in Earth’s crust When a volcano erupts hot gases and melted rock from deep within Earth find their way up to the surface They escape through the opening in the crust A volcano often looks like a mountain from the out side However on the inside a volcano is not a solid mass In December 2015 Nicaragua’s Momotombo volcano erupted for the first time in 110 years Until then it seemed like a quiet mountain WHAT IS A VOLCANO
7 Magma is molten or melted rock material within Earth VOCABULARY of rock The opening at the top of the volcano is called a crater If you were to look down into the crater you would see a hollow tube called a vent The vent runs from the crater down into a pool of magma below Earth’s surface Magma is contained in a space called a magma cham ber When a volcano erupts the magma travels up through the vent and exits through the crater Once magma comes aboveground it is called lava Some volcanoes may not erupt for hundreds or even thousands of years Volcanoes form when magma beneath Earth’s crust forces its way to the surface as this diagram shows
