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Chapter 9: Volcanoes• Mt. St. Helens in

1963

• Mt. St. Helens just

prior to the 1980

eruption

• Mt. St. Helens 2 years later

• http://www.dartmouth.edu/~volcano/images/DMSHp42.gif

Where is Mt. St. Helens?

http://www.washingtonstatesearch.com/Washington_maps/Potentially_Active_Volcanoes_Western_United_States_map.html

Mt. St. Helens 1980 Eruption

http://www.youtube.com/watch?v=vBJ9xZws7rohttp://www.youtube.com/watch?v=njV9ski1gB4&feature=related

Mt. St. Helens 2004 Eruptionhttp://www.youtube.com/watch?v=xt_nzZ7tL2A

• Subduction boundaries: an oceanic

plate plunges beneath another plate.

www.calstatela.edu/ faculty/acolvil/plates.html

• Occurs between an

oceanic and a continental plate. (Cascade Range)

• Occurs between 2

oceanic plates. (Mariana Islands, Pacific Ocean)

Subduction Boundary:Cascade Range

http://theextinctionprotocol.wordpress.com/2011/06/25/california-omen-rumblings-from-the-san-andreas-fault/

• Divergent boundaries: boundaries

between 2 lithospheric plates that are moving apart.

wrgis.wr.usgs.gov/ docs/parks/animate/

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• Divergent boundaries: boundaries

between 2 lithospheric plates that are moving apart.

http://www.youtube.com/watch?v=sgDM6m0lUGY

http://earth.leeds.ac.uk/dynamicearth/plates_move/hawaii.htm

Hot Spots

http://www.youtube.com/watch?v=bYv6V5EJAKc

Magma Types—BasalticLow silica content; low viscosity

(resistance to flow)

http://www.isd77.k12.mn.us/schools/dakota/kilauea.jpg

http://www.youtube.com/watch?NR=1&v=cPcuFHIVUcIhttp://www.youtube.com/watch?NR=1&v=2jc2fhiRoRQ

Magma Types—AndesiticHigher silica content; higher

viscosity

http://www.nhoem.state.nh.us/mitigation/Mt%20St%20Helens%20wo%20Frame.jpg

Magma Types—Rhyolitichighest silica content; highest

viscosity

http://www.swisseduc.ch/stromboli/perm/yellowstone/icons/gps1.jpg

http://www.youtube.com/watch?v=Ap_YUwdiy8I&NR=1http://www.youtube.com/watch?v=UJAwJeZiDsk&NR=1

Lava Flows--Basaltic

http://www.uib.no/People/nglhe/Musesidecontent/Pahoehoe%20Hawaii.jpghttp://www.calstatela.edu/faculty/acolvil/volcanos/aa.jpg

http://www.youtube.com/watch?v=qTTLYx4Xo2khttp://www.youtube.com/watch?v=iyIV5fd1Aww

aa (ah’-ah)

pahoehoe (pah hoy’ hoy)

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Lava Flows--Basaltic

Pillow lavahttp://www.youtube.com/watch?v=5G8W9sZtBTM

Pyroclastic Material--Ash

http://volcanoes.usgs.gov/Imgs/Jpg/Tephra/30410914-076_large.jpg

http://www.youtube.com/watch?v=tVVKADGYjg8

Pyroclastic Material--Lapilli

http://www.vulkaner.no/v/vulkinfo/pics/lapilli.jpg

Pyroclastic Material--Bombs

http://www.volcano.si.edu/volcanoes/region04/newzeal/whiteisl/2404whi2.jpg

http://www.youtube.com/watch?v=Jav4-GLXecQ

Pyroclastic Flow

http://www.uwiseismic.com/Images/volc_haz1lg.jpg

http://www.youtube.com/watch?v=vPRoTQYXwuY

Pyroclastic Flows

http://www.uwiseismic.com/Images/volc_haz1lg.jpg

http://www.uraniumminerals.com/Notes/Images/Pyroclastic_Flow.jpg

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Pyroclastic Flow: Pompeii, Italy, 79 CE

http://www.youtube.com/watch?v=8P352045O-o&feature=fvwrel

http://www.brandoquilici.com/all/img/volcanoes02_foto3.jpg

http://www.explorevolcanoes.com/Stromboli-volcano-italy.html

Mount Rainier? LaharA landslide of wet volcanic debris on the side of a

volcano

http://www.youtube.com/watch?v=N_cyG2dJPpc

9.3 Volcanic Landforms

http://www.coseti.org/images/hawaii%2099/big%20island/mvc-226x.jpg

http://vulcan.wr.usgs.gov/Imgs/Jpg/Shasta/Images/Shasta84_mount_shasta_with_shastina_1984.jpg

http://science.tjc.edu/Course/BIOLOGY/Colorado/capulin.jpg

Volcano: refers not only to the vent that allows magma to reach the surface, but also the landform

that results from lava hardening.

See p. 202-203 for drawing

Shield Volcano

http://www.cotf.edu/ete/images/modules/volcanoes/typesc.GIFhttp://geoimages.berkeley.edu/GeoImages/Johnson/Images/Large/CD3/051.jpg

http://www.willamette.edu/~mrother/shield%20volcano.jpg

• Low viscosity lava (basalt), so mild

eruptions

• Lots of lava

• Broad bases, gently sloping, massive

Cinder Cone Volcano

http://www.cotf.edu/ete/images/modules/volcanoes/typesc.GIFhttp://www.geo.wvu.edu/~jtoro/geol101/volcanoes/cinder%20cone.JPG

http://www.hawaiihighways.com/mauna-kea-cinder-cone-large.jpg

• Lava is thrown into the air

• Hardens before hitting ground

• Forms cone-shaped mound

Composite Volcano

http://www.cotf.edu/ete/images/modules/volcanoes/typesc.GIFhttp://earth.geol.ksu.edu/sgao/g100/plots/1008_composite_volc_Fujiyama.jpg

http://landslides.usgs.gov/recent/archives/images/mitch/img038.jpg

• Explosive; lava and pyroclastic materials

• Magma, water, & gases build up over time

• Narrow at top, broad base

• Cause lahars--flows of ash & melted snow

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Other Volcanic Landforms

http://volcanoes.usgs.gov/Imgs/Jpg/Aniakchak/dds40-039_med.jpghttp://www.dustydavis.com/blogimages/crater_lake_large.jpg

Caldera: when a volcano collapses, it forms a crater

Sometimes it fills with water…

Some are still active…

Other Volcanic Landforms

http://www.geolsoc.org.uk/photos/self3.jpghttp://image28.webshots.com/28/8/66/76/282586676mylvxG_ph.jpg

Lava plateau: long narrow crack in the Earth’s crust through which lava flows; forms a large flat area.