Transcript U4-T5.1-Types of Volcanoesx

Earth Systems 3209
Unit: 4
The Forces Within Earth
Reference:
Chapters 4, 15, 16, 19; Appendix A & B
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Unit 4:
Topic 5.1
Types of Volcanoes
Focus on . . .
 define volcano.
 describe the three types of volcanoes based on the following
criteria; width, slope, type of material, size and rock type.
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Types of Volcanoes
Volcano
 is an opening in Earth’s crust through which
igneous materials (lava, ash, cinder, and gases)
are erupted.
 Three different types of volcanoes exist;
1) Composite
2) Sheild
3) Cinder
Text Reference
Pages 96 - 101
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1. Composite or Stratovolcano
Characteristics:
 Large, nearly symmetrical structure formed from
alternating lava flows and pyroclastic debris.
 Most active composite cones are in a narrow zone
that encircles the Pacific (Pacific Ring of fire).
 These volcanoes are produced by very viscous
(thick) lavas mainly andesitic in composition.
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1. Composite or Stratovolcano
Characteristics:
 Display the most violent type of volcanic activity.
Erupting lava and pyroclastic material.
 Form a steep sided and relatively narrow base volcano
(up to 20 km wide) compared to shield.
 These volcanoes are found in mountainous environments
where oceanic – continental convergence occurs.
Ex. Andes Mountains.
 Examples of these volcanoes include;
Mount Mayon in the Phillipines, Mount Fuji in Japan, and
Mount St. HelensCopyright
In the
USA.
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Mt. St. Helens – a typical
composite volcano
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Mt. St. Helens following
the 1980 eruption
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2. Shield Volcano
Characteristics:
 Broad, slightly domed structure formed from fluid lava flows.
 These volcanoes are produced by lavas that display a
low viscosity and are mainly basaltic in composition.
 Form relatively wide base volcanoes compared to its
height and are the largest of the three types of volcanoes.
 These volcanoes are mainly found on the ocean floor along
divergent boundaries and hot spots.
 Examples of these volcanoes include;
Hawaiian Islands (Mauna Loa and Kilauea), & Midway Islands.
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2. Shield Volcano
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3. Ash & Cinder Volcano
Characteristics:
 Built mainly of ejected pyroclastic materials, such as,
ash and cinder.
 Volcanic cone has a very steep slope that is
usually less than 300 meters high.
 Form on the base of larger volcanoes and are
the smallest of the three types of volcanoes.
 Example: Paricutin in Mexico.
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A size comparison of the three
types of volcanoes
Shield volcanoes
are the largest reaching up to 100’s of
kilometers wide and up to 4 km above
sea level.
Composite volcanoes
are the second largest ranging in size
from 10’s of kilometers wide and up to
3 km high.
Cinder volcanoes
are the smallest approximately 1 – 2 km
wide and up to 300 meters (1000 ft) high.
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Volcano Type Characteristics
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Example 1:
Which is a characteristic of a shield volcano?
(A)
(B)
(C)
Width of Base
narrow
narrow
wide
Slope
gentle
steep
gentle
(D)
wide
steep
Which type of volcano can be found associated
with oceanic ridges?
(A) cinder
(C) shield
(B) composite
(D) strata
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Example 2:
What are small, steep-sided volcanoes made
of pyroclastic debris called?
(A) calderas
(B) cinder cones
(C) composite volcanoes
(D) shield volcanoes
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Your Turn . . .
Take the time and complete the following questions . . .
(Solutions to follow)
Questions:
Which type of volcano is the smallest with the steepest slope?
(A) cinder
(C) composite
(B) shield
(D) strato
At which location is a composite volcano formed?
(A) convergent plate boundary
(C) hot spot
(B) divergent plate boundary
(D) mid-ocean ridge
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Solutions . . .
Questions:
Which type of volcano is the smallest with the steepest slope?
(A) cinder
(C) composite
(B) shield
(D) strato
At which location is a composite volcano formed?
(A) convergent plate boundary
(C) hot spot
(B) divergent plate boundary
(D) mid-ocean ridge
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Summary . . .
Overview of Points covered:
Volcano
 is an opening in Earth’s crust through which igneous are erupted.
3 types of Volcanoes:
1) Composite
2) Shield
3) Cinder
 large, symmetrical
 alternating lava flows
& pyroclastic deposits
 broad
 slightly domed
 basaltic lava
 ejected pyroclastic materials
 steeply angled sides
 relatively small
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