Three different types of volcanoes exist; Volcano An opening in Earth’s crust through which igneous matter (lava, ash, cinder, and gases) are erupted. Reference: Pages: Volcanoes

a. Composite cones b. Shield volcanoes c. Cinder cones u broad u slightly domed u basaltic lava u ejected pyroclastic stuff u steeply angled sides u relatively small u large, symmetrical u alternating lava flows & pyroclastic deposits Volcanoes

A) Composite or Stratovolcano Large, nearly symmetrical structure formed from alternating lava flows and pyroclastic debris.  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.  Most active composite cones are in a narrow zone that encircles the Pacific (Pacific Ring of fire).  Volcanoes

A composite volcano

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 A) Composite or Stratovolcano

Mt. Fuji, Japan Mt. Mayon, Philippines u large, symmetrical u alternating lava flows & pyroclastic deposits u large, symmetrical u alternating lava flows & pyroclastic deposits Volcanoes

Cascade volcanic range: NW US Result of past/present subduction of oceanic crust Many volcanoes still active Mt. St. Helens

9500’ 8150’ (1350’ shorter!) Mt. St. Helens l Ejected nearly a cubic kilometer of ash & rock debris l 59 deaths l ash blown over 11 miles high!

Mt. St. Helens – a typical composite volcano

Mt. St. Helens following the 1980 eruption

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

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 B) Sheild Volcano

Hawaii Volcanoes MidWay

T&L Fig 4.C Hawaiian Islands

magma chamber Key terms: magma chambervent/pipecaldera 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.  Volcanoes

Sunset Crater – a cinder cone near Flagstaff, Arizona 1000 feet tall (900 years old)

Comparison of Volcano Types Composite volcanoesare the second largest ranging in size from 10’s of kilometers wide and up to 3 km high. are the largest reaching up to 100’s of kilometers wide and up to 4 km above sea level. Shield volcanoes are the smallest approximately 1 – 2 km wide and up to 300 meters (1000 ft) high. Cinder volcanoes Relative Sizes 5km Shield Volcano Composite Volcano Cinder Volcano Volcanoes

A size comparison of the three types of volcanoes Volcanoes

Volcano Type Characteristics