Download Volcano Types

Volcanoes
Volcano
An opening in Earth’s crust through which igneous
matter (lava, ash, cinder, and gases) are erupted.
Three different types of volcanoes exist;
Reference:
Pages: 95 - 101
Volcanoes
a. Composite cones  large, symmetrical
 alternating lava flows
& pyroclastic deposits
b. Shield volcanoes  broad
 slightly domed
 basaltic lava
c. Cinder cones
 ejected pyroclastic stuff
 steeply angled sides
 relatively small
Volcanoes
A) Composite or Stratovolcano
 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.
 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.
A composite volcano
Volcanoes
A) Composite or Stratovolcano
 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. Helens In the USA.
Volcanoes
Mt. Fuji, Japan
Mt. Mayon, Philippines
 large, symmetrical
 alternating lava flows
& pyroclastic deposits
Mt. St. Helens
Cascade volcanic range: NW US
•Result of past/present subduction of oceanic crust
•Many volcanoes still active
Mt. St. Helens
9500’
 Ejected nearly a
cubic kilometer of ash
& rock debris
 59 deaths
8150’
 ash blown over 11
miles high!
(1350’ shorter!)
Mt. St. Helens – a typical
composite volcano
Mt. St. Helens following the
1980 eruption
Volcanoes
B) Sheild Volcano
 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.
Volcanoes
B) Sheild Volcano
 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.
Volcanoes
MidWay
Hawaii
Hawaiian Islands
T&L Fig 4.C
Volcanoes
Key terms: magma chamber
vent/pipe
caldera
flank eruption
Volcanoes
C) Ash and Cinder Volcano
 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.
Sunset Crater – a cinder cone near
Flagstaff, Arizona
1000 feet tall
(900 years old)
Volcanoes
Comparison of Volcano Types
Composite volcanoes are the second largest ranging in size from
10’s of kilometers wide and up to 3 km high.
Shield volcanoes are the largest reaching up to 100’s of kilometers
wide and up to 4 km above sea level.
Cinder volcanoes are the smallest approximately 1 – 2 km
wide and up to 300 meters (1000 ft) high.
Relative Sizes
Shield Volcano
5km
Composite Volcano
Cinder Volcano
5km
Volcanoes
A size comparison of the three
types of volcanoes
Volcano Type Characteristics