8.3 TYPES OF VOLCANOES
Where the rock cycle begins
Learning Targets
1. Describe the basic shapes of volcanoes
2. Compare the features of volcanoes
3. Describe the stages in the formation of
volcanoes
How do volcanoes form?
1. Many layers of lava and ash mix together to
make a volcano
2. Different types of volcanoes form from
different mixes of ash, gas, and lava
Types of volcanoes
1. What are the 4 main types of
volcanoes?
a)
b)
c)
d)
Composite/Stratovolcano
Shield
Cinder cone
Supervolcano
2. Determined by type of magma and
type of eruption
Composite volcano Stratovolcano
1. Most famous type of volcano
2. Tall mountain with volcanic vent running
through the center
3. Viscous lava mixed with pyroclastic material;
i.e. composite
4. What does strata- mean?
a) Layer
5. Each eruption = one layer
Pyroclastic material held together with lava
Composite Volcano Eruption
Shield Volcano
1. Shaped like a shield laid flat
2. Wide, low volcanoes
a) Can be 100 miles wide
3. What type of eruption?
a) Effusive eruptions
4. What type of lava?
a) Low viscosity lava
5. No pyroclastic material
Shield Volcano Formation
Cinder Cones
1.
2.
3.
4.
Smallest and most common
Usually only erupt once
Sometimes form around other volcanoes
Formed by lava or pyroclastic material?
a) Only pyroclastic material; no lava
Cinder Cone Formation
Supervolcanoes
1.
2.
3.
4.
Huge volcanic features
Eruptions so powerful only a caldera remains
A caldera is a Volcanic Crater
Eruptions are rare, but can change global climate
and life on earth
5. A lot is unknown due to rarity of eruptions
Caldera of a Supervolcano
Mt. Pinatubo Eruption; not a supervolcano
Last Yellowstone supervolcano supereruption: 640,000 years ago
Yellowstone
Magma Chamber
Mt. Pinatubo
Magma Chamber
Types of volcanoes and causes
1. Composite
a) Subduction zones
2. Shield
a) Hot spots
3. Cinder cone
a) Variable
4. Supervolcano
a) Enormous hot spots under continents
8.4 VOLCANIC LANDFORMS
Where the rock cycle begins
Learning Targets
1. List and describe landforms created by lava
2. Explain how magma creates different
landforms
3. Describe the processes that create hot
springs and geysers.
Volcanic features
1. Lava can form
a) Lava domes: reforming volcanoes
b) Lava plateaus: lava erupted on flat ground
c) Volcanic islands: Island arc or hot spot chain
d) What type of rock is this? Extrusive Igneous
2. Magma can form
a) Intrusive igneous rocks
 Small
pebbles to huge batholiths
Growing Lava Dome
Crater Lake; Caldera with Lava Dome
Cascades Lava Plateau
Lava Plateau: Like a flood that becomes solid rock
Remains of ancient magma (intrusive)
Hot springs and Geysers
1. Water reacts with nearby magma to form
a) Hot springs: hot water under normal pressure
b) Geysers: hot water that erupts under high
pressure
2. Why might people think this water has
medicinal properties?
a) Hot water holds a lot of minerals
Edge of Pyroclastic Flow