Volcanoes
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A volcano is an area of the Earth's surface where magma and volcanic gases are expelled. The inside of a volcano has a magma chamber where all the magma is "held" underground, and vents where the magma is expelled from the volcano and becomes lava. There are two types of volcanic eruptions, nonexplosive and explosive eruptions. Nonexplosive eruptions are the most common type of eruptions. They produce calm flows of huge amounts of lava. The majority of the Earth's surface, including the seafloor and the Northwest region of the U.S. are covered with lava from nonexplosive eruptions. Explosive eruptions are rarer than nonexplosive eruptions. They cause molten rock to be blown into the atmosphere in tiny particles. The tiny particles, called ash, can reach the Earth's atmosphere and can circle the Earth for years and years. While larger pieces of debris fall closer to the volcano. An explosive eruption can blast millions of tons of lava and rock from a volcano. There are three types of volcanoes, the three types are cinder cone, shield, and composite volcanoes. A cinder cone volcano is made of pyroclastic material produced by explosive eruptions. The pyroclastic material forms steep slopes on the side of the volcano. A shield volcano is made by layers of lava released by repeated nonexplosive eruptions. Even thought the side on a shield volcano aren't very steep, they can be very enormous. A composite volcano is one of the most common volcano and is sometimes called a stratovolcanoes.
Holt Science & Technology: Earth Science Pages 250-252 and 257
Holt Science & Technology: Earth Science Pages 250-252 and 257