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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Volcanism and Volcanic Hazards
Geology 11 Principles of GeologyA. M. P. Tengonciang & D.D. N. javier
Department of Physical SciencesUniversity of the Philippines, Baguio
Volcanism
Encompasses all processes associated with the transfer of molten rock and gases from the interior of the Earth to its surface
Volcano an opening in the crust through which molten lava and gases erupt
Eruption when magma rises from its source or from a storage reservoir and reaches the Earths surface
Why does magma rise?
Physical properties (temperature, composition, viscosity, relative buoyancy)
Input of fresh magma into magma reservoir Pushes magma upwards
Can cause magma chamber to expand/break
Degassing Magma becomes less dense
The gas exerts pressure on overlying & surrounding rocks
Squeezed out by overlying & surrounding rocks
Eruption styles
Effusive dominated by the outpouring of lava onto the ground
http://mail.colonial.net/~rpavlik/pavlikweb/images/geohazitem_143.jpghttp://www.nrcan.gc.ca/sites/www.nrcan.gc.ca.earth-
sciences/files/images/whitehorse/images/img74.jpg
Lava fountain
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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2006 effusive eruption, Mayon volcano, Albay
Eruption styles
Effusive dominated by the outpouring of lava onto the ground
Explosive fragmentation of magma caused by exsolution & expansion of magmatic gases
Eruption mechanisms
Decompression and exsolution of magmatic gas
Interaction of water with ascending magma explosive!!!
Explosivity of eruptions is affected by
Composition (silica content)
Temperature
Dissolved gases
SiO2 MAGMATYPE
TEMP. (oC) VISCOSITY GASCONTENT
ERUPTION STYLE
~50% mafic ~1100 low low nonexplosive
~60% intermediate ~1000 intermediate intermediate intermediate
~70% felsic ~800 high high explosive
Ref: http://www.geology.sdsu.edu/how_volcanoes_work/Controls.html
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Magma viscosity
Viscosity
the degree to which a substance resists flow
depends on T, composition, & gas content (H2O, CO2, SO2, H2S, SO3, CO, COS, CH4, HCl, HF, H2, O2, N2, CS2, NH4, B, Br)
In silicate magmas, SiO4
4- tends to polymerize by sharing oxygens, forming irregularly-shaped groupings
silica content, T, gas content = viscosity
http://upload.wikimedia.org/wikipedia/commons/b/b7/Viscosity.gif
Products of eruption1. Lava
Aa -characterized by a rough or rubbly surface composed of broken lava blocks called clinker
Pahoehoe -smooth, billowy, undulating, or ropy surface
Pillows
2. Pyroclastic material (Tephra)
ash (64 mm)
3. volcanic gases
water vapor, H2O
carbon dioxide, CO2sulfur dioxide, SO2 and others
Aa lava Pahoehoe lava
Pillow lava
- typically formed when lava emerges from an underwater volcanic vent or a lava flow enters the ocean
http://farm4.static.flickr.com/3154/2882768195_fefd780424_o.jpghttps://en.wikipedia.org/wiki/File:Nur05018.jpg
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Products of eruption
2. Pyroclastic material (Tephra)
ash (64 mm)
Volcanic ash shards from Mt Erebus, AntarcticaField of view = 400 microns
http://geoinfo.nmt.edu/labs/microprobe/images/bit161-big.jpg
Mount Pinatubo ash
http://volcanoes.usgs.gov/ash/build/32923351-028_large.jpghttp://www.uwec.edu/jolhm/EH2/Lennon/ash.jpg
Lapilli (also called cinders)Andesitic lapilli scoria from Mt St Helenshttp://eiu.edu/~cfrbj/parks/MSHE/lapilli.jpg
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Volcanic bombs
http://volcanoes.usgs.gov/Imgs/Jpg/Photoglossary/30410914-028_large.JPG
Volcanic bombs are usually expelled while molten
http://www.sfll.bnu.edu.cn/default///Unit%209%20of%20HW/Volcanic%20Bombs.files/cowpieB.jpg
http://www.sfll.bnu.edu.cn/default///Unit%209%20of%20HW/Volcanic%20Bombs.files/brdcrst2.jpg
http://www.sfll.bnu.edu.cn/default///Unit%209%20of%20HW/Volcanic%20Bombs.files/fusiform3.jpg
Volcanic block- solid rock fragment greater than 64 mm in diameter that was ejected from a volcano during an explosive eruption
http://volcanoes.usgs.gov/images/pglossary/block.php http://www.volcano.si.edu
Volcanic gases
water vapor, H2O
carbon dioxide, CO2 sulfur dioxide, SO2 hydrochloric acid, HCl
hydrogen fluoride, HF
hydrogen sulfide, H2S
carbon monoxide, CO
hydrogen gas, H2 ammonia, NH3 methane, CH4 tetrafluorosilane, SiF4
Gases in Magmas
Major gases
Water vapor (H2O)
Carbon dioxide (CO2)
Nitrogen (N2)
Minor gases
Sulfur compounds (SO2, H2SO4, etc.)
Carbon monoxide (CO)
Chlorine (Cl2)
Fluorine (F2, HF)
High silica (rhyolitic) magmas generally have more gas than low silica (basaltic) magmas
H2O 67.7
CO2 12.7
N2 7.65
SO2 7.03
SO3 1.86
S2 1.04
H2 0.75
CO 0.67
Cl2 0.41
Ar 0.20
Gases from a Hawaiian volcano
Mayon releasing gas
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Volcanic landforms
1. Pyroclastic cones
Small volcanoes that grow from thousands of recurring incandescent jets made of molten-to-plastic lumps of magma (scoria, UK/cinders, US)
Form steep-sided mounds with a small summit crater
Commonly occur in clusters or on the flanks of other volcanoes (e.g. shield volcanoes)
http://www.earthonlinemedia.com/ebooks/tpe_3
e/volcanic_landforms/volcano_types_2.html
Puu Oo cinder cone
http://en.wikipedia.org/wiki/File:Puu_Oo_-_Crater_Lava_pond_1990.jpg
1946 eruption
Paricutin cinder cone, Mexico
http://en.wikipedia.org/wiki/File:Paricutin_30_612.jpg
http://en.wikipedia.org/wiki/File:Paricutin_30_613.jpg
Cinder cone in 1943
http://en.wikipedia.org/wiki/File:Paricutin.jpg
Paricutin in 1994
Sunset Crater
http://volcano.oregonstate.edu/sunset-craters
(Tarbuck, E. J., Lutgens, F.K., & Tasa, D. 2009. GEODe: Earth Science v.3)
http://taaltours.blogspot.com/
http://en.m.wikipedia.org/wiki/Tagaytay_City
Binintiang Malaki, Taal Home on a cinder cone
http://realestate.yahoo.com/promo/the-home-at-the-top-of-a-volcano.html
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Volcanic landforms
2. Composite volcanoes (aka stratovolcanoes)
Made of innumerable layers of:
pyroclastic material
lava flow deposits
rubble derived from the flow & break-up of brittle lava & dome rocks
http://web.gccaz.edu/~lnewman/gph111/topic_un
its/Igneous_Vulcanism/14_23d.jpg
Volcanic landforms
Composite volcanoes (aka stratovolcanoes)
Build a framework that support the growth of volcanoes with great heights
Most stand isolated several tens of km apart in elongate chainshttp://web.gccaz.edu/~lnewman/gph111/topic_un
its/Igneous_Vulcanism/14_23d.jpg
Volcanic landforms
Composite volcanoes (aka stratovolcanoes)
Constructed from multiple eruptions spanning a few hundred to hundreds of thousands of years
http://web.gccaz.edu/~lnewman/gph111/topic_un
its/Igneous_Vulcanism/14_23d.jpg
SE NW
35-4032-40
From A. Tengonciang
Klyuchevskaya volcano, Kamchatka peninsula, Russia
http://www.volcano.si.edu/volcano.cfm?vn=300260
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Mount St. Helens, Washington, USABefore and after eruption
http://www.lethist.lautre.net/mt_st_helens2.jpg
http://pubs.usgs.gov/circ/c1050/fig49.jpg
Mount St. Helens, Washington, USA before and after eruption
Volcanic landforms3. Shield volcanoes
Broad with low slopes, like overturned shields
Constructed of solidified lava that was originally very fluid, moving at speeds up to 12 km/hr
Fast lavas can flow long distances, to construct gentle slopes & broad summits, forming lava plateaus
(Tarbuck, E. J., Lutgens, F.K., & Tasa, D. 2009. GEODe: Earth Science v.3)
http://clasfaculty.ucdenver.edu/callen/1202/Battle/Build/VolcanicEx/Extrusive.html
4. Calderas
Spanish, cauldron
Large craters that form when the ground surface above a partially empty magma chamber collapses into the void
Dimensions may range from a few km to as large as 60 km in diameter
Volcanic landforms
http://en.wikipedia.org/wiki/File:Taal_Volcano_satellite_image.gif
www.volcano.si.edu
Taal Caldera Lake
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Photo credit: A. Tengonciang
Pinatubo caldera lake
http://64.19.142.11/upload.wikimedia.org/wikipedia/commons/thu
mb/1/14/Santorini_Landsat.jpg/280px-Santorini_Landsat.jpg
http://upload.wikimedia.org/wikipedia/commons/0/0c/The_Santorini_Caldera.jpg
Santorini caldera, Greece
http://en.wikipedia.org/wiki/File:Ia_Santorini-2009-1.JPG
http://www.volcano.si.edu/volcano.cfm?vn=212040
View of Santorini caldera walls
Eruption on May 27, 1883
Anak Krakatau, May 17, 1997.
Kaguyak volcano, Alaska
http://en.wikipedia.org/wiki/File:MountKaguyak.jpg
Volcanic landforms
5. Domes
Domes result from the slow extrusion of highly viscous magma
May start as highly explosive eruptions that wane into slow, viscous lava extrusion, forming thick stubby flows or bulbous domes
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Santiaguito volcanic dome complex in Santa Maria volcano, Guatemala
http://www.photovolcanica.com/VolcanoInfo/Santiaguito/Gua07_0528.jpg
http://volcanoes.usgs.gov/activity/methods/deformation/tilt/msh.php
Dome
http://en.wikipedia.org/wiki/File:PaodeAcucar.JPG
Sugarloaf Mountain, Rio de Janeiro
(granite-gneiss dome) Volcanic landforms
6. Maar
A small volcano with a wide crater of diameters ranging from several hundred meters to 1-2 km
Form from steam explosions that occur when rising magma comes into contact and mixes with groundwater or surface water
Seven Lakes of San Pablo, Laguna
http://cdn1.vtourist.com/15/5108108-the_7_lakes_San_Pablo_City.jpg
http://www.pinoymountaineer.com/2008/08/seven-lakes-of-san-pablo.html
Maar de Tazenat, Chane des Puys, France
http://dichamp.pagesperso-orange.fr/englishversion/prinvolce/tazenate.html
Mount Tabaro
http://64.19.142.12/upload.wikimedia.org/wikipedia/commons/thu
mb/a/a2/Taal_volcano_crater.jpg/300px-Taal_volcano_crater.jpg
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Volcanic landforms
7. Lava plateau (e.g. Giants Causeway , Northern Ireland)
http://matadornetwork.com/trips/60-mind-bending-rock-
formations-from-around-the-world-pics/
Flood Basalts
Large volume outpourings of basaltic magma from fissure vents
Examples: Laki (Iceland), Columbia River Plateau (Washington, Oregon), Deccan Traps (India), Siberian Traps (Russia)
Flood Basalt:Laki, Iceland, 1783
Largest basalt eruption in recorded history
Basalt erupted from a 32 km long fissure
Covered an area of 565 km2 with 13 km3 of lava.
http://64.19.142.11/images.intellicast.com/App_Images/Article/175_18.jpg
http://www.geog.cam.ac.uk/research/projects/eruptions/figures.html
Factors that determine the morphology of a volcanic feature
What is a volcanic hazard?
A volcanic hazard refers to any potentially dangerous volcanic process (e.g. lava flows, pyroclastic flows).
What is a volcanic risk?A volcanic risk is any potential loss or damage as a result of the volcanic hazard that might be incurred by persons, property, etc. or which negatively impacts the productive capacity/sustainability of a population.
Volcanic hazards video
Ash falls
Hot ash flows
Mudflows
Volcanic landslides
Volcanic tsunami
Lava flows
Volcanic gases
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Benefits of Volcanism
1. Hot springs2. Geothermal
energy3. Oxygen4. Global cooling5. Fertile soil6. Natural beauty
Hot springs and geysers
Bacon-Manito, Philippines
How do we know if a volcano is active?
Active erupted during the last 10,000 yrs.
Inactive no activity during the last 10,000 yrs.
How many volcanoes are there in the Philippines?
22 active volcanoes and more than 200 inactive
most active is Mayon Volcano with 47 historical eruptions
7 active volcanoes are being monitored by PHIVOLCS
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Geol. 11 Volcanism & Volcanic Hazards
2nd Sem AY 2013-14 U.P. Baguio
1/11/2014
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Global Distribution of Volcanoes
DIGIT, 2002
Some uses of igneous rocks
Basalt - road pavement
Granite and rhyolite decorative stone
Pumice - abrasives
Andesite and diorite - material for retaining walls
Obsidian ornamental stone