Issue 13 Science Read 10 Jul Career Guidance Interesting Science Real Life Application Real Time News Lower Secondary About volcanoes Crystal Wicker 29 May 2015 What is a volcano? A volcano is a mountain that opens downward 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. Volcano eruptions have been known to knock down entire forests. An erupting volcano can trigger tsunamis, flash floods, earthquakes, mudflows and rock falls.
How are volcanoes formed? Volcanoes are formed when magma from within the Earth s upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger. What are the different stages of volcanoes? Scientists have categorized volcanoes into three main categories: active, dormant, and extinct. For those that have erupted and there is a possibility that it may erupt soon. A dormant volcano is one which has not erupted in a long time but there is a possibility it can erupt in the future. An extinct volcano is one which has erupted thousands of years ago and there s no possibility of eruption.
Why do volcanoes erupt? The Earth s crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. The friction causes earthquakes and volcanic eruptions near the edges of the plates. The theory that explains this process is called plate tectonics. What are plate tectonics? The theory of plate tectonics is an interesting story of continents drifting from place to place breaking apart, colliding, and grinding against each other. The plate tectonic theory is supported by a wide range of evidence that considers the earth s crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. The plates are all moving in different directions and at different speeds. Sometimes the plates crash together, pull apart or
sideswipe each other. When this happens, it commonly results in earthquakes. How many volcanoes are there? There are more than 1500 active volcanoes on the Earth. We currently know of 80 or more which are under the oceans. What is the difference between lava and magma? Magma is liquid rock inside a volcano. Lava is liquid rock (magma) that flows out of a volcano. Fresh lava glows red hot to white hot as it flows. What is a pyroclastic flow? A pyroclastic flow is a fluidized mixture of solid to semi-solid fragments and hot, expanding gases that flows down the sides of a volcano. These awesome features are heavier-than-air emulsions that move much like a snow avalanche, except that they are fiercely hot, contain toxic gases, and move at phenomenal, hurricane-force speeds. They are the most deadly of all volcanic phenomena.
Which is the largest active volcano? The world s largest, active volcano is Mauna Loa in Hawaii, where famous coffee is grown in the rich volcanic soils. Mauna Loa is 13,677 feet above sea level. From its base below sea level to its summit, Mauna Loa is taller than Mount Everest.
What is the Ring of Fire? The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean. The Ring of Fire has 452 volcanoes and is home to over 50% of the world s active and dormant volcanoes. Ninety percent of the world s earthquakes and 81% of the world s largest earthquakes occur along the Ring of Fire.
When is a volcano considered active? Surprisingly, there is no consensus among volcanologists on how to define an active volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth s volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of activity. Given the long lifespan of such volcanoes, they are very active. By our lifespans, however, they are not. What is a Vulcanian Eruption? A vulcanian eruption is a type of explosive eruption that ejects new lava fragments that do not take on a rounded shape during their light through the air. This may be because the lava is too viscous or already solidified. These moderate-sized explosive eruptions commonly eject a large proportion of volcanic ash and also bread crust bombs and block.
Power Words dormant temporarily inactive tsunami an unusually large sea wave produced by a seaquake or undersea volcanic eruption. mantle the portion of the earth, about 1800 miles (2900 km) thick, between the crust and the core. avalanche a large mass of snow, ice, etc., detached from a mountain slope and sliding or falling suddenly downward consensus a general agreement Article adapted from: http://www.weatherwizkids.com/?page_id=98
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