Download volcanoes

Do Now:
1. What is convection?
2. In which layer does convection take place?
3. What is the heat source for convection?
4. Which layer makes up the tectonic plates?
5. What types of landforms are created at divergent
boundaries?
6. What types of landforms are created at
convergent boundaries?
VOLCANOES!!!!!!
• http://www.youtube.com/watch?v=jRfEGv
p6wDU
• Take 1 minute to read the questions at the top
of your guided video notes and be prepared to
answer them in complete sentences during the
video!
Map of Volcanoes around
the WORLD!
Volcano Discovery
• http://webcams.volcanodiscovery.com/Kilau
ea
• This site allows you to look at what is currently
happening around the world with volcanoes
and earthquakes!
What is the difference between
magma and lava?
• REVIEW: What is the type of rock that forms when
magma cools and hardens?
Magma is below the Earth and forms intrusive igneous rock
• What type of rocks forms when lava cools and
hardens?
Lava is what comes out of the volcano and forms
extrusive igneous rock
• THEY ARE BOTH TYPES OF IGNEOUS ROCK!
What’s the difference?! –Think location…
How a volcano erupts is based
on viscosity.
1. What is viscosity?
• Viscosity is how resistant a substance is to
flowing. For example, honey is more viscous
than water.
• Magma that contains more silica will be more
viscous, magma that contains less silica will be
less viscous.
Magma that is very viscous will explode,
magma that is less viscous will flow.
Lava that is hotter will be less viscous (like if
you heat up honey) and will flow more.
Lava contains dissolved gases, and if the
lava is very viscous, those bubbles cannot
expand. Instead, the bubbles will explode
upwards.
Viscosi – what?!
• If the Shield volcano has faster flowing lava that
creates new land, does it have a high viscosity or
low viscosity?
• If the Composite Cone has a slower flowing lava
that explodes due to the high content of silica,
does it have a high viscosity or low viscosity?
HOT SPOTS!
• Volcanic regions that are fed by the mantle
below and are much hotter than the mantle in
other parts of the world
• Occur at divergent boundaries
Convergent vs. Divergent
• Divergent boundaries form hot spots – ex:
Hawaiian islands and the RING OF FIRE – shield
volcanoes, composite cones, etc.
• Convergent boundaries form volcanic island arcs.
These form over subduction zones
• The plate that is subducted releases water into the
overriding plate and causes some rock to melt – ex:
Alaska volcanoes or Mt. St. Helens – cinder cones
• http://www.youtube.com/watch?v=9CxhOpk3J7Y
Anticipation Guide!
Volcanoes also eject
pyroclastic materials,
• These particles can be as small as ash or as
large as boulders.
There are 3 main types of volcanoes, but
they all have this general form:
Shield Volcanoes
Shield Volcanoes
• Made of very fluid lava that spread really far
and hardened.
• Broad shape
• Lots of island volcanoes (for example, Hawaii)
• Eruptions are not very violent
• Hot spot or subduction?
Cinder cone volcanoes
Cinder cone volcanoes
• Ejects lots of cinders (chunks of pyroclastic
material) that accumulate at the bottom.
• Steep sides
• Short lifespans (usually only erupt once).
• Usually pretty small
• Hot spot or subduction?
Composite cone
volcanoes
Composite cone
volcanoes
• Huge!
• Produce both lava and pyroclastic material that
can reach up to 120 mph!
• Usually found in the Ring of Fire, which is a zone
of volcanoes that circles the Pacific Ocean.
• Can sometimes form lahars, which are mudflows
that are made when lava mixes with water and
soil.
• Hot spot or subduction?
Shape Review
Build your own virtual
volcano
• Let’s explore some more and build our own
virtual volcano to test eruption types
Let’s explore other types
of volcanoes
Calderas
• Calderas are volcanic depressions that are
created when the magma chamber is drained
and the volcano collapses in on itself. Instead
of looking like a mountain, it looks like a valley.
Volcanic necks
• Volcanic necks are formed when a volcano has
been weathered down so that only the magma
conduit (pipe) is left.
Lava plateaus are made from very low-viscosity
lava flowing out of a fissure (crack) in the
ground. The lava spreads really far and creates
a flat landform.
Review:
1. What is the relationship between the temperature
of magma and its viscosity? The higher the
temperature, the more or less viscous the magma.
2. Name the three types of volcanoes AND list them
in the order of least to most violent.
3. What region of the world are the most violent
volcanoes found?
4. Draw a diagram of a cinder cone volcano and
lable the main parts (conduit, vent, crater,
lava/pyroclastic material)