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I. VOLCANOES AND PLATE TECTONICS
A. General
1. Some eruptions more powerful than ________________________________________
2. __________ of many eruptions - __________________________________________.
a. Plate movement driven by _____________________________________________.
B. ____________
1. _________________________ produced ____________________ Earth’s surface
2. Forms under three conditions:
a. If rock temperature ___________________ melting point of minerals rock is
_________________________, rock will ____________
b. Rock _____________ when excess _______________ is removed from rock
already above its ______________________________
c. Adding _________________________ may decrease the melting point of some
minerals in the rock and cause it ____________________
C. _______________________
1. Any activity that includes the _________________________ toward or onto
____________________________
2. __________ - _______________ that flows _________ Earth’s surface
3. _______________ - a ____________________ in Earth’s surface through which
_______________________________ are expelled
4. Magma rises upward through the crust because the magma is _________________
that the surrounding rock
a. As bodies of magma rise toward surface, they become _______________________
1) Because they are ____________, they can ___________ some of the
surrounding rock.
2) As magma rises, it is _________________________________ in the
surrounding rock.
5. As lava flows from opening, or ____________, the material may build up as a _______
or may eventually form ________________________
D. Major Volcanic Zones
1. Most active volcanoes and earthquakes occur in ______________________________
_______________________________________________
2. ______________________ - major zone of active volcanoes encircling the _________
a. Formed by the _____________________________ along the Pacific coasts of
North America, South America, Asia, and the islands of the western Pacific
E. Three Types of Volcano Formation
1. Many volcanoes located along __________________________ where one tectonic
plate moves _________________________________
a. When ____________________ lithosphere plate meets _____________________
lithosphere plate, the __________________ oceanic lithosphere moves
_______________________ the continental lithosphere.
b. A _______________________ forms on the ocean ___________ where the plate is
________________________
c. Continental plate ___________________________ to form a line of ____________
along _______________________
d. Sinking rocks ____________ to form ____________________
e. Sometimes some magma breaks through overriding plate ____________________
and form _________________________________
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1) ex. Coast Range (_____________________________)
f. If _________________________ edges collide, a string of volcanic mountains called
an ___________________________ forms on the overriding plate.
1) As more magma reaches the surface, islands may become _____________
+ join to __________________________________
2) ex: _________________, Aleutian Islands
2. ___________________________________________
a. The ____________________________ of magma erupts where plates __________
b. Forms __________________________________________.
1) Most eruptions _________________________________ because they are
__________________________________________
2) ex. Surtsey Island in Iceland (1963)
3. __________________________
a. Volcanically active area of Earth’s surface ________________________________
b. Most form where columns of _______________________________ from
_____________________________mantle called ______________________
rise + reach lithosphere
1) The magma breaks through ________________________________
c. Volcanoes form _________________________________ of tectonic plate
d. __________ over mantle plume keeps ________________________ so surface
volcano is eventually ______________________________ from mantle plume
1) Volcano’s activity ___________ as it moves _____________ from hot spot
e. ____________________________________ over mantle plume
1)Volcanoes increasingly _________________________ they are from hot spot
f. ex. _____________________________________________
F. _______________________ Activity
1. As magma moves upward, it _____________________________________ overlying
rock
2. Because of magma’s high temperature, magma affects ________________________
in a variety of ways
a. It may __________________________________ rock.
b. Rock falling into magma may _____________, or rock may combine with the new
___________________ rock (rock formed from cooled magma)
c. Magma may cool + solidify ______________ crust to form __________________
igneous rocks
G. _______________________ Volcanoes
1. ____ Volcanic Regions
a. ___________________ in hazard area
1) _________________________
2) ___________________________________________
3) ___________________________________________
b. Many _______________________________ in area
2. ____________________ volcanoes
a. Both in southern _______________________ in __________________ California
1) Mt. ______________
2) Mt. ______________ – most recent eruption ____________
II. VOLCANIC ERUPTIONS
A. ______________________ of Magma
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1. _________ - rich in ______________________________, generally ________ in color
a. made of ___________________ or upper _______________ rock
b. make _____________ lava that cover _____________ areas
2. __________ - rich in ____________________________, generally _________ in color
a. made of _______________________ rock
b. forms _________________ lava that flows easily but ______________________
3. Most ____________________ crust – ____________
4. Most ____________________ crust - _________________________________ rock
B. Types of _______________________
1. Force of eruption depends on _________________, or resistance _____________, of
magma
a. Viscosity determined by amount of _____________________________
2. _______________________ eruptions caused by _______________________ magma
a. Large amounts of trapped, __________________________ which build up
___________________ (shaking can of soda)
b. ______________ temperatures and high silica content (_____________) magma
c. Throw volcanic fragments and ___________ widely
d. ________________ doesn’t flow very far
1) Builds ______________________________ volcanoes
2) Often at _________________zones or where only continental crust involved
a) ex. Yellowstone Caldera
3. ______________ eruptions caused by ______________________________ magma
a. __________________ escape easily (glass of soda going flat)
b. Hotter magma, __________ rich (____________________ magma)
c. _______________________________ that build gentle slopes
1) _____________________ volcanoes
d. ______________________ volcanoes like midocean ridge and those in Hawaii
C. Types of Lava Flows
1. When mafic lava ______________________________, a crust forms on the surface
a. Pahoehoe forms if ___________________ lava continues to flow after crust forms
causing wrinkled rocks
1) Has _______________________________ texture
2. Aa - _____________________________ forms if crust deforms rapidly or grows too
thick to form _______________________ and breaks
a. Lava has same composition as pahoehoe
b. Texture results from differences in _______________________ and the rate and
slope of the ______________________________
D. Pyroclastics
1. ___________________________________ that form during a volcanic eruption
a. Formed from ____________________ lava
b. Some form as magma breaks because of rapidly expanding _______________
during an eruption
c. Others form as fragments of erupting lava ________________________ as they fly
through the air
2. Classified according to particle size
a. Volcanic ___________ - __________________ 0.25 mm in diameter
b. Volcanic ___________ - __________________ 2 mm in diameter
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c. Volcanic ____________ - large clots of lava which are thrown out of an erupting
volcano while they are red-hot, then cool and develop a round or spindle shape
d. Volcanic ___________ - the largest pyroclastic materials which form from solid rock
blasted from the vent
E. Volcano Anatomy
1. ________________ - funnel-shaped ______ at the top of a volcanic vent
a. Becomes wider as weathering + erosion break down crater walls
1) Loose materials sometimes ____________________________________
2. ________________ - a large, circular depression that forms when the magma
chamber below a volcano partially ________________ and causes the ground above
to __________________
a. May later fill with water to _________________________
3. Types of volcanoes
a. ____________________________ – __________________, not very wide, made
of felsic lava, ____________________ eruptions
b. _______________________ – ________________________, made of mafic lava,
_______________________ eruptions
c. ________________________ – in between shape, fairly large, ________________
explosions and quiet lava flows, also called stratovolcanoes
F. Predicting Eruptions
1. Strength + frequency of ____________________________ may increase
2. Upward movement of magma beneath surface may cause surface of volcano to
_________________________________________
3. Study previous eruptions of a __________________________ volcano
a. _____________________________________ volcanoes have been studied long
enough to establish any patterns
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