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Volcanoes
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Volcanoes are mountains with a vent from which molten material from deep within the earth can spew under the appropriate conditions. Volcanoes have existed for geologic eons, but many are no longer active. The number of volcanoes worldwide that earth scientists consider active—those that can erupt—was about five hundred in the mid-1990s. Volcanoes are usually located at the junction of the earth's lithospheric plates. In the United States most active volcanoes are located in Alaska or in Hawaii, which consists of a group of islands formed by earlier volcanic eruptions. The West Coast of the continental United States ... has a relatively inactive volcanic zone.
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Volcanoes are the most powerful natural events on earth. They contain more energy than earthquakes, hurricanes, and tsunamis. Volcanic landscapes are some of the most beautiful on earth. Many of the great mountains, lakes, and islands of the world were formed by volcanic activity. Over three quarters of the world's surface has been modified by volcanic eruptions or lava flows. Most volcanoes form at the junction of tectonic plates in subduction zones, or rift zones.
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Volcanoes figure prominently in the mythology of many peoples who have learned to live with eruptions, but science was late in recognizing the important role of volcanism in the evolution of the Earth. As late as 1768, the first edition of Encyclopædia Britannica gave voice to a common misconception by defining volcanoes as “burning mountains, which probably are made up of sulphur and some other matter proper to ferment with it, and take fire.” Today geologists agree that volcanism is a profound process resulting from the thermal evolution of planetary bodies. Heat does not easily escape from large bodies such as the Earth by the processes of conduction or radiation. Instead, heat is transferred from the Earth's interior largely by convection—that is, the partial melting of the Earth's crust and mantle and the buoyant rise of magma to the surface. Volcanoes are the surface sign of this thermal process. Their roots reach deep inside the Earth, and their fruits are hurled high into the atmosphere.
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Children Will Have a 'Lava' Fun Learning About Science With Scholastic's The Magic School Bus Volcano Adventure Activity Center July 31 /PRNewswire/ -- Volcanoes have intrigued people of all ages for many years. And while the volatile Mayon Volcano near Legazpi, Philippines, continues to be a threat, on the other side of the world picturesque Mount Rainier in Seattle has been dormant for more than 150 years. Dormant and active volcanoes have many different elements, and now children ages 6 to 10 can learn about these and other volcanoes through Microsoft Corp.'s newest science software, Scholastic's The Magic School Bus(R) Volcano Adventure Activity Center. The software encourages kids to scale a mountain of intriguing information about volcanoes on land, under water and in space.
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Volcanoes have been called the thermostat of the planet. They wreak havoc, but ... spawn far-ranging benefits for soil and air. Some earth scientists now say that the vast swath of destruction from a volcanic eruption can be a source of creation....
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Volcanoes can be caused by "mantle plumes". These so-called "hotspots" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are ... found elsewhere in the solar system, especially on rocky planets and moons.
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