Download Volcanoes - Great Hearts Archway Chandler

Volcano Notes for Website
Volcanoes – are openings in Earth’s crust from which lava, solid rock fragments (cinders), gases and ash erupt.
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They are formed in 3 locations
 Convergent boundaries – two plates moving toward each other
Most common at convergent boundaries where the heat and pressure melts rock into magma,
which can rise through cracks in the crust.
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Divergent Boudaries – two plates moving away from each other
Plates are pulling apart and magma rises through the cracks to form volcanic mountains and midocean ridges.
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Hot Spots – {Pizza analogy. Earth’s crust is like a pizza crust. Hard to get dough even, sometimes
you have thin spots of dough. Just like the Earth’s crust. So then you have all the hot sauce that’s
bubbly and what happens to the crust?} Most of the hot spots occur under the ocean. Magma
pushes through thin parts of the Earth’s crust. Islands like Hawaii were formed like this. This is how
we have volcanoes that are not near the plate boundaries.
There are 3 types of volcanoes – they are classified based on how they form
Composite volcano (strato-volcano)
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Most common type – over 60% are composite
Usually formed at convergent boundaries
Sometimes they have runny lava layers, other times the have pyroclastic materials form
layers.
Have a cone shape, wide base, steep sides, multiple vents, and a crater
Examples: Mount Fuji –Japan, Mount Saint Helen’s – USA, Mount Vesuvius - Italy
Cinder cone volcano –
 sudden, violent eruption; can be pyroclastic (see note below)
 creates hills made of many small pieces of hardened lava, called cinders (very airy little
rocks b/c they had so many bubbles but cooled so quickly)
 formed from ash, cinders, dust- pyroclastic material
 steep-sided, cone-shaped mound, but not very tall (usually less than 1000ft),
 simplest structure, single vent
 Mt. Paricutin, Mexico and Mt. Isalco, El Salvador
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Shield Volcano –
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Formed from gentle eruptions of “runny” lava (Pahoehoe).
Usually formed over hot spots.
Very wide, not too steep.
Biggest type of volcanoes (because they are so wide)
Tallest mountain in the world is Mauna Kea (measures from sea floor to top)
Examples: Mauna Loa and Hawaiian Islands
Pyroclastic flow • dense, destructive mass of very hot ash, lava fragments, and gases ejected
explosively from a volcano and typically flowing downslope at great speed.
Caldera - is a large depression created when the magma chamber empties and the top of the volcano collapses
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Give students the Volcano Labeling Diagram for them to cut out and glue into spirals. Although we have three
different kinds of volcanoes, they have the same basic parts.
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Further Classification
 Active – those that erupt with some degree of regularity. About 1400 active volcanoes in the
world; over half are in 8 countries (Russia, Indonesia, U.S., Japan, Chile, Ethiopia, Philippines,
Iceland)
 Dormant – “Sleeping” volcano that might erupt again if pressure builds to make it active again
 Extinct – only when a volcano has not erupted in many thousands of years and will not erupt
again. Volcanoes become extinct because they have moved away from the geological event
that caused eruptions. They are usually eroded at the surface.
Also in their spiral notebooks, students will paste in the “The Volcano” labeling worksheet.