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Volcanoes

Page history last edited by PBworks 12 years, 11 months ago

VOLCANOES

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot, molten rock, ash and gases to escape from below the surface. Volcanoes are lava that builds up into a hill or a mountain.

 

  • A vent is an opening in the volcano through which lava and rock fragments erupt.
  • A crater is a bowl-like depression at the summit of the volcano, and is often the location of the vent.

 

Types of Volcanoes:

 

Shield Volcano - a gently sloping volcanic mountain that heaps up when basaltic magma is too viscous to form a lava plateau. Sides of a shield volcano slope away from the vent at a slight slope varying between 6 and 12 degrees. These volcanoes can be considered quiet volcanoes, as their eruptions are not violent. The lava which produces these volcanoes is not viscous, that is, it flows somewhat easily.Fissures are linear cracks in the sides of the volcano that are formed after a shield volcano erupts and the fluid lava flows over the edge

of the crater.

 

Cinder Cone - a small volcano (up to 400 meters) composed of pyroclastic fragments that come out of the central vent at a great speed. When large amounts of gas accumulate withing rising magma, a cinder cone forms. These volcanoes produce explosive eruptions, as the trapped gases are released. The lava which produces these volcanoes is more viscous.

 

    • Image:Rinjani 1994.jpg Toes of a pāhoehoe advance across a road in Kalapana on the east rift zone of Kīlauea Volcano in Hawaii.

(A volcanoe erupting in Idonesia- Lombok at Mount Rinjani in 1995) (Lava which has been erupted and flowing into the roads of Kalapana in Hawaii)

 

Submarine Volcano - are common in the ocean floors. Only a few are active, in shallow water blasting steam, and rocky debris high above the surface of the sea is evidence of an eruption. Many of these types of volcanoes are found deep within the sea that the weight of the water above prevents the explosive release of steam and gases. Usually even the big submarine explosive do not disturb the oceans surface. Pillow lava is a common eruptive product of submarine volcanoes.

 

Image:Nur05018.jpg

(Pillow Lava which was left after a submarine explosion in the ocean)

 

 

 

 

Measuring A Volcano:

 

Volcanoes can be measured in many different ways. Measuring a volcano is important so that we can tell apart the explosion, compare eruptions and to see how strong the eruption is. A few methods of measuring are colour coding the eruption. The colors in the color code are Green, Yellow, Orange, and Red. Another way to find out measurements is a number scale from 0 to 5. 0 being the weakest and 5 being the strongest.

 

COLOR CODE:**

Green - No eruption expected volcano is in normal form.

Yellow - An eruption is able to happen in several weeks and may happen with no warning.

Orange - Massive eruption is able to happen in several days and might happen with no warning. Ash puffs should not get up to 25,000 feet above sea level. Opening of lava dome may happen.

Red - Major eruption expected in a day or less.

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Fun Facts

  • Indonesia has about 400 volcanoes but only 100 are considered active.
  • Thousands of years ago under-sea volcanoes erupted and formed islands of Hawaii.
  • The biggest volcano in the world is Mauna Loa in Hawaii.
  • Jupiter's moon is considered to be the most volcanic place in the solar system.
  • Right now there are 1,500 active volcanoes in the world and all of them have erupted in the past 10, 000 years.

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