General Occurrence of Volcanoes

• The Pacific Ring of Fire.
  
  Volcanoes are generally associated with plate tectonics. At the plate edges, where one plate is in collision with another, or where plates are moving apart, volcanoes can be found. A typical example of this is around the Pacific Ocean, an area commonly known as the Pacific Ring of Fire. Volcanoes stretch from the southernmost tip of South America all the way through North America over to Japan and back down through Southeastern Asia.
  
  

The Main Parts of a Volcano

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  The Cone
  
  The cone is the most striking part of the volcano and can usually been seen from many miles. Cones vary in size and shape, depending on the type of magma that is emanating from that particular volcano. High-sided steep cones are typical of granitic magma, which is viscous and slow moving. Low to almost flat volcanoes, or shield volcanoes, are products of basaltic magmas that are extremely fluid and fast moving. The volcanoes of Hawaii are typical basaltic volcanoes.
  
  The Vent
  
  The vent supplies the magma from the underlying magma source to the top of the volcano. They can be almost straight or convoluted.
  
  The Magma Chamber
  
  The source of the magma is the underlying magma chamber. It may be shallow or many miles under the Earth's surface.
  
  

Secondary Features

• Volcanoes are unstable and, during an eruption secondary, vents can go out from the main vent and breakout on the slope off the volcano. There, they form a secondary cone. This may be seen in the diagram above.
  
  

The Biggest, Tallest and Most Active

• Mauna Loa and Her Four Sisters.
  
  The biggest, tallest and most active volcano on the Earth is Mauna Loa, on the island of Hawaii. The main island of Hawaii is made up of Mauna Loa and four other sister volcanoes. If it were measured from its base below sea level to its summit, Mauna Loa would be almost 56,000 feet high. Mauna Loa has erupted 33 times since records began being kept in 1843.
  
  

The Most Violent Eruption

• The most violent eruption the world has ever seen was on Aug. 27, 1883, when the island of Krakatoa disappeared after the volcano of the same name exploded. The island was approximately 492 yards high before the blast; after, it was approximately 273 yards below sea level. The noise of the explosion was heard around the world. It is estimated that more than 36,400 people died as a direct result of this explosion.