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Volcano (Hindi : ज्वालामुखी पर्वत| Bengali : আগ্নেয়গিরি | Tamil : எரிமலை | Telugu:అగ్నిపర్వతం | Urdu: آتش فشاں


A volcano is a rupture on the earth’s crust that opens to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over or fill the air with lava fragments. Eruptions can cause lateral blasts, lava flows, hot ash flows, mudslides, avalanches, falling ash and floods. Earth’s volcanoes occur because the planet’s crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in the Earth’s mantle.[1] Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging.

Quick Facts

  •  The word volcano originally comes from the name of the Roman god of fire, Vulcan. The Romans first used the term to describe Mt. Etna, a volcanic mountain they believed was the forge of Vulcan.
  • More than 80% of the Earth’s surface, including above and below sea level, was formed by volcanoes.
  • Lava is molten rock from a volcano that has reached the Earth’s surface. Molten rock below the Earth’s surface is referred to as magma.
  • Cinder cones are the most common volcanoes, steep conical hills with a vent and a crater at the summit, usually no more than 1,000 feet high. Examples: Sunset Crater Arizona, Lassen Peak in California, and San Quintin Volcanic Field in Baja, Mexico.
  • Composite volcanoes or stratovolcanoes are the symmetrical, cone-shaped, and have a conduit system through which magma flows to the surface through one or more vents, can reach 8,000 feet in height. Examples: Mount St. Helens, Mount Fuji, Redoubt, Pinatubo, Soufriere Hills and Mount Pelée in Martinique.
  • Lava domes are the small masses of lava that accumulate around and over the volcano’s vent, then cool to break apart flowing down the dome’s side. They commonly occur inside the crater of large stratovolcanoes or composite volcanoes. Example: Augustine Volcano in Alaska
  • Shield volcanoes are formed when fluid lava cools to form a gently sloping hill. The largest group of volcanoes on Earth is of this type. Examples: Mauna Loa and Mauna Kea in Hawaii, Eyjafjallajokull and Grimsvotn in Iceland, and Novarupta in Alaska.
  • There are more than 500 volcanoes that have erupted at least once in the world, and 50 of those are located in the United States.
  • More than 50% of the world’s active volcanoes above sea level encircle the Pacific Ocean, forming the “Ring of Fire.” The ring starts at New Zealand, goes north around the eastern coast of Asia to the Aleutian Islands, and south down the western coasts of North, Central and South America. Volcanoes are usually located where tectonic plates meet.
  • The biggest known volcano in our solar system is actually on Mars. Its name is Olympus Mons and it measures a whooping 600km (373 miles) wide and 21km (13 miles) high.
  • Common volcanic gases include water vapor, carbon dioxide, sulfur dioxide, hydrogen chloride, hydrogen fluoride and hydrogen sulfide.
  • Pumice is a unique volcanic rock (igneous) that can float in water. It can also be used as an abrasive and is sometimes used in beauty salons for removing dry skin.
  • Well into the Middle Ages, many believed volcanoes were entrances into the fiery underworld.
  • During the past 400 years, nearly a quarter of a million people have been killed as a direct result of volcanic eruptions. Indirect aftereffects such as famine, climate change, and disease most likely have tripled that number.
  • Many scientists believe that all the water on the earth was originally vented into the atmosphere by volcanoes.
  • Volcanologists use a special electric thermometer called a “thermocouple” to take a volcano’s temperature. Lava is so hot that a glass thermometer would melt.
  • Highly volcanic areas have some of the most fertile farmland in the world. Volcanic eruptions bring nutrients such as potassium and phosphorus to the Earth’s soil. The weathering of volcanic rocks also releases nutrients.’
  • The material ejected from a volcano is called “pyroclastic flow” from the Greek pyro (fire) and I (broken). It includes small fragments of rock, frothy pumice, and large boulders. Pyroclastic flow can reach temperatures of 212° F and can rocket down the side of a mountain at 155 m.p.h.
  • In 1963, an undersea volcano created the newest land mass on Earth, Surtsey Island, which lies off the southwest coast of Iceland. Today Surtsey is about 1 sq. mile and is named after Surt, a fire giant from Norse mythology.
  • The eruption of Mount St. Helens on May 18, 1980 had 500 times the power of an atomic bomb. Geologists considered this a moderate eruption.
  • In 1660, the people of Naples were shocked to find what looked like little black crosses raining down on them. While they thought it was proof that St. Januarius was looking out for them, the crosses were really twin pyroxene crystals which Mt. Vesuvius spewed out of its crater. Vesuvius last erupted in 1944.
  • New ocean floor is created when two oceanic plates move apart and magma bubbles up to fill the rift. This is called a rift volcano. Through this process, the Atlantic Ocean is widening by 2 cm. per year, and the East Pacific Rise is widening by 20 cm. a year. In 10 million years, the East Pacific Rise will be 1,240 miles wider.
  • Some volcanic islands such as Iceland and Hawaii have black beaches. Their sand is made from basalt, an igneous rock formed when lava cools and has been broken down into sand particles.
  • In some volcanic areas such as Iceland, heat energy from magma can be used to warm water and run power plants. This type of energy is called geothermal (earth heat) energy.
  • Yellowstone National Park in Wyoming sits on the site of an ancient supervoclano. It erupted around 2 million years ago, 1.3 million years ago, and 640,000 years ago. If it follows the same pattern, another eruption is due any time now.
  • Japan has 10% of the world’s active volcanoes.
  • An acid lake in the crater of Kawah-Idjen in Indonesia absorbs gases rising from the volcano, creating a lake so toxic it can burn through human flesh in minutes.

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