Download Chapter 9: Volcanoes

Chapter 9: Volcanoes
9.1: How and Where Volcanoes Form
 Volcano
a. Opening in Earth’s crust through which _______________, gases, and ash __________
b. The ____________________ that develops around this __________
A. Magma Formation
1. Magma = __________ rock, formed deep within Earth
2. Volcanic __________ occur when magma rises to the surface
3. Three conditions allow __________ to form:
a. __________ in pressure __________ melting temperatures (mid ocean ridge rift
valleys)
b. __________ in temperature (hot spot—Hawaiian Islands)
c. __________ in amount of water in asthenosphere, __________ melting
temperatures (subduction boundaries)
4. Magma formation can occur at __________ and ____________________ boundaries
5. Once magma forms, it __________ to the surface because its density is __________ than
____________________ materials
6. Characteristics and rising rates depend on __________ content.
B. At Subduction Boundaries
1. Volcanoes always form on the __________ plate
2. Oceanic-__________ collision = volcanoes form on __________
3. Oceanic-__________ collision = volcanic ____________________
C. At Divergent Boundaries
1. Lower __________, lower __________ point, and high __________ cause large amounts
of magma to form.
2. Most magma reaches Earth’s surface at __________ boundaries (mid-ocean ridges)
3. Mid-ocean ridges are locations of most __________ activity
4. ____________________ Mid-Atlantic ridge is above water
D. Over Hot Spots
1. Areas of volcanic activity that result from __________ of hot material that have risen from
deep in Earth’s __________
2. Sources may be 670 to __________ beneath the surface
3. Hot spots remain in the same place as the ____________________ plate moves across it
4. __________ Islands formed as the Pacific Plate moved northwest over a ______________
5. __________ volcanoes lie directly over the hot spot, __________ volcanoes or seamounts
indicate past location of plate over hot spot
6. __________ is the newest volcanic island forming off the coast of __________
9.2: Magma and Erupted Materials
A. Types of Magma
1. __________ determines a magma’s viscosity (__________ to flow)
2. __________ silica content magmas __________ flow (__________ viscosity)
 Andesitic and rhyolitic __________
Chapter 9 Student Notes
Volcanoes
Page 1 of 3
3. __________ silica magmas flow more __________ (__________ viscosity)
 Basaltic __________
4. __________ (water vapor and carbon dioxide) dissolve in magmas at depths where they
form and may ____________________ as the magmas rise
5. Gases escape __________ from basaltic magmas, but are more __________ released from
more __________ magmas
6. Basaltic magmas form at __________ and oceanic ____________________
7. Andesitic magmas tend to form at ____________________ boundaries
8. Rhyolitic magmas form where ____________________ underlie __________ plates
B. Lava Flows
1. Magma that reaches Earth’s surface is called __________
2. The composition of __________ may differ from magma due to materials being
__________ or ____________________ the magma as it rises
3. Lava Flows on Land
a. Basaltic flows are associated with ____________________ eruptions and form
__________ rocks as they cool
b. Pahoehoe (formed by basaltic lava at high temperatures flowing quickly out of
vents) has __________, ropelike surfaces
c. Aa (formed by cooler basaltic lava that moves more slowly) has __________,
jagged surfaces
4. Underwater Lava Flows
a. Forms ___________ shape—rounded, _______________ form with a hard crust
b. Results in __________ of rounded lumps called __________ lava
C. Ash and Rock Fragments
1. When trapped __________ are released, solid fragments (pyroclastic material) may be
__________
2. Pyroclastic __________ are classified by __________
a. __________ —diameters less than 2 mm
b. __________ —diameters from 2 to 64 mm
c. ____________________ —diameters greater than 64 mm
3. Violent eruptions can create pyroclastic __________ (combination of pyroclastic material
and ____________________)
a. Mount ________________ eruption buried Pompeii under a pyroclastic flow of
__________ and __________
9.3: Volcanic Landforms
A. Shield Volcanoes
1. __________ bases and __________ sloping sides
2. __________ lava, __________ explosive, frequent and copious
B. Cinder Cones
1. Forms when __________ lava is thrown into the ___________ from a vent
2. Lava breaks into _______________, hardens, hits the ground
3. Fragments accumulate, forming a ________________ mound with an __________ base
4. ___________ than other types of volcanoes, form in groups on sides of __________
volcanoes
Chapter 9 Student Notes
Volcanoes
Page 2 of 3
C. Composite Volcanoes
1. Develop when __________ of materials from successive explosions accumulate around the
__________
2. Composed of __________ lava flows and pyroclastic __________
3. Mount _____________ 1980 eruption illustrates forces that shape __________ volcanoes
4. Most _______________ volcanoes have __________ eruptions followed by long periods
of time remaining relatively __________
D. Calderas
1. Large ___________________ basins formed after the top of a volcano __________
2. ____________________ in Oregon is an example of a ____________
3. The caldera in _______________ National Park is still active
i. Magma _______________ water feeding __________ springs and __________
ii. Estimates indicate the eruption that created Yellowstone caldera was __________
times more powerful than the _________ Mount St. Helens eruption
E. Lava Plateaus
1. Formed when __________ lava pours from a ___________ in the Earth’s surface
2. Lava spreads across the land, forming the ___________________
3. __________ Plateau (NW United States) is over _________ thick and covers 164,000 km2
9.4: Extraterrestrial Vulcanism
A. The Moon
1. __________ consist of __________ lava flows that occurred 3-4 __________ years ago
2. Photographs of an ______________ crater filled with lava indicate that the lava is
_______________ than the crater
3. ____________ rock samples of lunar lava are __________ billion years old
4. ____________ lava rock samples are __________ billion years old
B. Mars
1. Has numerous __________ volcanoes
2. Olympus Mons is the __________ known volcano in the ________________
i. __________ across the base
ii. __________ above the surrounding terrain
3. Large size indicates that Mars ________________ have ______________ plates
4. Are volcanoes on Mars still __________?
5. Could volcanoes on Mars __________ in the future?
C. Venus
1. More than 1600 large ________________, most are ____________ volcanoes
2. ____________________ and ____________ are also found on the surface
3. Volcanic ____________ could account for __________ surface temperature and
accumulated ___________ in the atmosphere
D. Io
1. One of the most volcanically __________ places in the _______________
2. Caught in ______________ tug of war between ____________ and two other moons
i. Results in parts of Io’s _________ moving up and down by as much as _________
ii. Resulting ____________ is the source of heat that powers ____________ activity
3. __________ temperatures at Pillan Patera volcano may be as high as __________
Chapter 9 Student Notes
Volcanoes
Page 3 of 3