Volcanoes Around the World

By Ashley H.


      Volcanoes look a lot like mountains, but they aren't the same as a mountain. Mountains are made a different way than a volcano.  A volcano builds itself up.  It does this by the magma which comes out of it.  The magma builds up on the outside of the volcano, making it taller.

    Down below the surface of Earth is the mantle.  When the rock in this mantle becomes too hot because of extreme temperatures, it melts and forces itself up as magma through the crust and up to the surface. Here it releases pent-up gases and the volcano erupts.  Once this magma has reached the surface, it is called lava.  However, there are many types of lava, and some are slower than others.  Some move more quickly though.  It all depends on the type of rock that is melted inside the mantle.

    A great number of the volcanoes that erupt around the world occur on plate boundaries.  Volcanoes occur at convergent boundaries, divergent boundaries, and hot spots.  An example of a volcano located at a convergent boundary would be the stratovolcano Mt. St. Helens in Washington State.  A hot spot causes shield volcanoes such as the ones which created the Hawaiian Islands down in the Pacific Ocean.  The divergent boundaries can also cause shield volcanoes which are known to have sloping sides because of the slow moving lava.
 
 



Mount Pinatubo

  On June 12 through the 15, 1991, Mount Pinatubo erupted after it had been dormant for 6o years.  This volcano is located 100 kilometers from Manila in the Philippines.  5 billion cubic meters of ash was ejected from the volcano during the eruption which makes this one of the most gigantic eruptions of the century.    58,000 citizens that were located near the volcano when warning signs became visible evacuated the area and by the time the volcano had erupted, 100.000 people had been evacuated.  14,500 military personal also left the area before the eruption.

    This volcano actually changed the Earth's climate. The sulfuric acid droplets from the volcano in the stratosphere covered the entire planet.  The energy from the sun was blocked from the Earth, so the Earth in turn just cooled off.  This droplets causes other damage to the Earth as well.  They not only blocked the sun, but caused low ozone levels.  Indirectly, the sulfuric acid made other problems.  If you would like to learn more about this eruption and the effects it had on Earth, please click on the title to this section to be taken directly to another site.

Tambora

  On April 5, 1815, an explosion was heard.  A lieutenant sent to boats out to investigate since they believed that another ship was possibly in danger.  In time, they would find it was actually the tambora volcano coming to life.  The actual eruption of the volcano on April 10 killed 10,000 people on Soembawa and other surrounding islands.  In addition, 82,000 other lives would end from malnutrition and diseases.

    This 4,200 meter high volcano had suddenly become much smaller.  On April 17 the eruption ended.  The volcano had now shrunk to 2,850 meters.  Tambora had ejected about 1,700,000 tons of debrea.  The volcano didn't exactly leave the city peaceful for a while.  It actually rumbled for about 3 months after the 17th of April.  To learn more about Tambora, please click on the italicized title above.
 
 

Hazards of Volcanoes

  There are 12 different types of volcanic hazards.  Some are more hazardous than others. These types of hazards are volcanic earthquakes, directed blast, tephra, volcanic gases, lava flows, debris,  avalanches, landslides, and tsunamis, pyroclastic surge, pyroclastic flows, and lahars.  The least dangerous of all these is the lava flows because the lava moves so slowly that there is usually enough time to evacuate the area where the volcano is located before the lava ever reaches a city or kills someone. Lahars on the other hand are one of the most dangerous volcanic hazards.  Lahars usually move much quicker than any other hazard and can float automobiles, sea crafts, and buildings.

    Falling ash is yet another type of volcanic hazard.  Pent-up gases erupt violently from this explosive eruption.  These eruptions are all dangerous in some ways, but not all are as dangerous to human life.  We can usually escape from the hazards of a volcano before anyone is killed or injured when the type of hazard in progress can be detected soon enough or the eruption is slow enough for residents nearby to escape.  To learn more on the hazards of a volcano, just click on the title of the section and you will be taken directly to another site for more information.
 
 


                                           

Causes of Eruptions

    Eruptions are caused  when rock in the mantle is heated and melted.  Since the solid rock is so much denser than the heated rock or magma, the magma rises to the top and flows out of the volcano onto the surface.  Here the magma is defined as lava.  How the magma is exploded onto the surface all depends on the form of magma.  When these eruptions take place a volcano is described as active rather than dormant.  To learn more about this subject, please take the time to click on the title to this paragraph and read what other sites have to contribute.

Signs That An Eruption is Likely

    Previous eruptions contribute to the forecasting of when another eruption will take place and where.  These past volcanoes can be mapped on a graph to show where other eruptions are likely.  Many times, scientists can find a pattern of a certain volcano.  Predicting any volcano may help to save numerous lives.  Learning about volcanoes can also help us prepare for an eruption so that less damage is done. There are warning signs that can help to realize when a volcanic eruption is taking place.  Magma will collect in the chambers in the volcano and gas may begin escaping from the inside of the layers of rock.  If you would like to learn more, please click on the title to this paragraph.