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Volcano eruptions

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					Volcanoes
       Oh the pressure!
Deep within the
Earth, rock exists
as a hot liquid
called magma.

This magma is
found in pockets
called magma
chambers.
A volcanic eruption begins when this
underground molten rock builds up pressure.

When under great
pressure magma can
hold many dissolved
gases.

As the magma rises
through the rock layers, the pressure
decreases.
Since the pressure of the magma is
decreasing, the gases in the magma escape
in an explosive blast at the surface.

When magma reaches
the surface it is called
lava.
               The place where lava
               erupts is called a vent.
               Some volcanoes have
               more than one vent.
Not all volcanic eruptions are alike. If the
magma is thin and fluid, there is
usually a quiet eruption.

Magma rich in silica tends to be thick. This
type of magma tends to trap water vapor, so
therefore the eruptions tend to be very
explosive.          http://video.pbs.org/video/1485211138/

    example:
   Mt. St. Helens
Types of eruptions (we’re going over 6-
there are many more)
                                            Plinian
towering ash plumes                         serious damage
                                            fast moving lava
Hawaiian
  not very destructive or explosive
              sluggish low gas lava flows
                                     Strombolian
                                    eruptions not dangerous
                                    no lava flows (usually)
                                    produce ashy tephra
                       Vulcanian Types of eruptions
                   many short explosions eruptions initiated
by high gas magma, can launch football sized pyroclasts,
generally not associated with a lava flow.
Hydrovolcanic (Sursteyan)
               hot magma heats water
               to produce steam, can melt
               snow causing mudslides and               Fissure
               major flooding       occurs when magma flows up
                if it occurs through cracks and leaks out onto
               undersea-     the surface, characterized by curtain
               Highly        of fire, can produce slow moving,
               explosive            heavy flows
http://www.cleanvideosearch.com/media/action/yt/watch?videoId=_sRw_e5RA34
www.guardian.co.uk/world/video/2011/nov/14/congo-nyamuragira-volcano-eruption-video


         Other eruption types of note….
                     Vesuvian-lots of ash-laden gas
                     violently discharged


                 Phreatic-steam blast eruption; driven by explosive
                 expanding steam-no new magma-just solid rock
                 thrown out

    ‘
Pelean (or nuee ardente)-large amount of
gas, dust, ash and incandesent lava pieces,
roll down the flanks at speeds as great
as 100 mph.
Magma can sometimes
be so thick that it can
clog up a vent.

This causes the pressure
underneath to increase
leading to a more
explosive eruption.
        -demonstration!!
   Explosive Eruption Demonstration
Materials:
  baking soda                 dish soap
  Alka seltzer                vinegar
  red food coloring           cork
  small soda bottle           goggles
1. Place dry ingredients in bottle. Add the dish
soap and food coloring to this mixture.
2. Put on safety goggles.
3. Quickly pour vinegar in and immediately put
the cork into the bottle opening. Stand back!
Volcanic eruptions assignments

You will have 2 days to complete these
assignments.
http://dsc.discovery.com/convergence/krakatoa/virtualvolcano/virtualvolcano.html

      1. Volcanic eruptions webquest (websites
under activity information and worksheet under
documents on teacherweb page)
      2. volcano paper model and questions (done
in lab notebook)
      3. volcano poem and artwork (write and
http://www1.bellevuepublicschools.org/curriculum/k6web/sixthgrade.html
        http://web.ccsd.k12.wy.us/techcurr/Science/06/science.html
                 http://sciencespot.net/Pages/classearth.html
                 http://coolsciencelab.com/sixth_grade.htm
    http://www.spacegrant.hawaii.edu/class_acts/VolcanologyDoc.html
                 http://sciencespot.net/Media/volcanoht.pdf
             http://education.usgs.gov/primary.html#volcanoes
                    http://jc-schools.net/ppts-science.html

				
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posted:4/17/2012
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