Download Volcanoes

Introduction to Volcanoes
Our Objectives Today
I Can…
• Describe the Anatomy of a Volcanoes
• Explain the formation of a Volcanoes
– Relates to Location
• Identify the Possible Locations of
Volcanoes
– Relates to plate Boundaries
• Identify Types of Volcanoes
Origin of the word: Volcano
• The word 'volcano' comes from the little island of Vulcano in the
Mediterranean Sea off Sicily. Centuries ago, the people living in this area
believed that Vulcano was the chimney of the forge of Vulcan - the
blacksmith of the Roman gods. They thought that the hot lava fragments
and clouds of dust erupting form Vulcano came from Vulcan's forge as he
beat out thunderbolts for Jupiter, king of the gods, and weapons for Mars,
the god of war.
Anatomy of a Volcano
Anatomy of a Volcano
Anatomy of a Volcano: Caldera
• Calderas are formed
when the top of the
volcano collapses
Anatomy of a Volcano: Caldera
• Fissures are cracks or
tears on or near volcanos
where lava ma flow from.
Anatomy of a Volcano: Caldera
• Lava Dome – as the magma
is forced upward a protrusion
forms on the volcano.
Anatomy of a Volcano: Caldera
• Tephra – materials
that are ejected from the
volcano. They can be any
size (as seen below).
Formation of Volcanoes
• Rock melts deep in the earth forming magma
• Magma is less dense than rock so it rises to the
surfaces
• Magma flows out through vents (openings on
the surface)
• Lava flows out of vents and begins to cool and
becomes igneous rock
• This process occurs year to year and the
igneous rock continues to form from the cooling
lava.
Recall Unit 4: Intrusive vs. Extrusive Igneous Rock
• The size of grain (crystal) depended on the rate of cooling.
Formation of Volcanoes
Location of Volcanoes
• Divergent Plate Boundaries
– Ex: Iceland which is located along the Mid-Atlantic Ridge
• Convergent Plate Boundaries (subduction zones)
– Ex: Mount St. Helen (WA) Mount Shasta (CA)
– Magma forms when one plate slides beneath another plate and
begins to melt
– Magma is then forced to the surface
• Hot Spots
– Ex: Hawaiian islands
– Formed by unusually hot magma that melts the earth’s crust
Location of Volcanoes
Location of Volcanoes
Location of Volcanoes
• Divergent Plate Boundaries
Location of Volcanoes
• Convergent Plate Boundaries
Location of Volcanoes
• Hot Spots
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– hot spot develop above hotter-than-usual
areas of the mantle.
• Magma generated by the hot spot rises through
plates and produces active volcanoes at the
Earth's surface.
– As oceanic volcanoes move away from the
hot spot, they cool and subside, producing
older islands, atolls, and seamounts.
• As continental volcanoes move away from the hot
spot, they cool, subside, and become extinct.
Location of Volcanoes
Forms of Volcanoes
Shield Volcanoes
• Forms from the build up of quiet eruptions
through vents or fissures
– Resembles a warriors shield
• Has gently sloping sides
• Basaltic lava flows from here
Shield Volcanoes
Shield Volcanoes
Forms of Volcanoes
Cinder Cone Volcanoes
• Forms from the build up of explosive
eruptions
– Bits of rock called tephra are blown into the
air and fall to the ground. Over time the sides
of this volcano forms
• Resembles a giant cone
– Very steep side with loosely packed stone
Cinder Cone Volcanoes
Cinder Cone Volcanoes
Forms of Volcanoes
Composite Volcanoes
• Intermediate between cinder cone and
shield volcanoes
• Eruptions vary; some may be explosive
others quiet (more next section)
• Alternating layers of tephra and lava form
the sides of the volcano
• Found near subduction zones
Composite Volcanoes
composite volcano
Composite Volcanoes
Composite Volcanoes
Forms of Volcanoes
More Volcano Types
Our Objectives Today were…
Can I…
• Describe the Anatomy of a Volcanoes
• Explain the formation of a Volcanoes
– Relates to Location
• Identify the Possible Locations of
Volcanoes
– Relates to plate Boundaries
• Identify Types of Volcanoes