1. Volcanoes
Katelyn Kilgore

2. What volcanoes are…
• An opening in the
planet’s crust
• Causes volcanic
ashes and gases to
escape
• Found where plates
are diverging or
converging

3. Vulcanism
• Magma is expelled
onto the surface (still
molten)
• Magma solidifies on
the surface
• Magma solidifies far
below the surface

4. Volcanism
• Lava- magma that has
departed and has
contacted with the
surface
• Rock fragments
• Solidified lava blobs
• Ashes
• Dust
• Gas
• steam

5. Distribution
• About 550 active
volcanoes
• Surface and
underwater eruptions
• Associated with plate
boundaries

6. Factors of an eruption
• Surface crust strength
• Pressure
• Chemicals
– Silica (SiO2) is believed
to be the main source of
very explosive eruptions
– Low silica content
usually produces more of
a fluid explosion

7. Classifications
• Broad
• Sloping gently
• Layers of lava flow
• “quiet” eruptions
• Examples: Hawaiian
Islands and Tahiti

8. Classifications
• Large and steep
• Lava flows,
pyroclastics, hardened
mud flow deposits
• Both “quiet” and
explosive eruptions
• Examples: Mt. Fuji, Mt.
Rainier, Mt. Shasta, Mt.
Vesuvius, Mt. St.
Helens

9. Classifications
• Small and sometimes an
irregular shape
• Plug of lava that is
covered by pyroclastics
(frequently occurs in the
crater of Composite
Volcano)
• Examples: Lassen Peak,
Mono Craters

10. Classifications
• Small and steep sided
• May be composed of
ash or cinder-sized
pieces
• Produces “quiet” and
explosive eruptions
• Examples: Paricutin,
Sunset Crater

11. Other Classifications
• Caldera- produced
when volcano
explodes and/or
collapses
• Volcanic Neck-
small, sharp spire
that rises abruptly
above the
surrounding land

12. Hazards
• Lava Flows
– Rarely cause loss of life
– Does damage to the area
around it
– Either moves fast or
slow
– Flow on predictable
paths

13. Hazards
• Eruption Column and
Clouds
– Consists of pyroclastic
material and gases
– Volcanic ash and dust
form a cloud
– Volcanic bombs
– Can damage crops and
collapse buildings

14. Hazards
• Pyroclastic Flows
– Avalanche of hot gases,
ash, and rock fragments
– Also called nuée ardente
– Burns and buries
anything in its path

15. Hazards
• Volcanic Mudflows
– Caused by heavy rain or
melting of snow and
glaciers
– Water combined with ash
and pyroclastic flow
– Fast-moving slurry of
mud and boulders
– Buries the valley floor
– Also known as Lahars

16. Can it be prevented?
• Unfortunately no,
because it is a natural
occurrence all we
can do is be prepared
for when a volcano
blows its top.

17. Works Cited
Fisher, Richard V. "The Volcano Information Center." Volcano Information
Center (VIC). Web. 07 Dec. 2011. <http://volcanology.geol.ucsb.edu/>.
McKnight, Tom L., and Darrel Hess. "Chapter 14 The Internal Processes.“
Physical Geography: a Landscape Appreciation. Eighth ed. Upper
Saddle River, NJ: Prentice Hall, 2005. Print.
Topinka, Lyn. "CVO Menu - Volcanic Hazards, Features, and Phenomena.“
USGS Cascades Volcano Observatory (CVO). 30 Jan. 2003. Web. 07
Dec. 2011. <http://vulcan.wr.usgs.gov/Glossary/framework.html>.
"Volcano - Credo Reference Topic." Credo Reference Home. Web. 07 Dec. 2011.
<http://www.credoreference.com/topic/volcano>.
"Volcano | Define Volcano at Dictionary.com." Dictionary.com | Find the Meanings
and Definitions of Words at Dictionary.com. Web. 07 Dec. 2011.
<http://dictionary.reference.com/browse/volcano>.
"Volcano." Wikipedia, the Free Encyclopedia. Web. 07 Dec. 2011.
<http://en.wikipedia.org/wiki/Volcano>.