Science of Natural Disasters-Week 2-Volcanoes - … of Natural Disasters: Volcanoes! ... Indonesia 1772 Ash flows. ... Science of Natural Disasters-Week 2-Volcanoes Author:

Science of Natural Disasters: Volcanoes!

13 April 2016

Rebecca ClottsDepartment of Geology, University of St Thomas

What is a volcano?

“…and it was then I saw how, in the hole, the ground swelled and raised itself 2 or 2.5 meters high, and a kind of smoke or fine dust -- grey, like ashes -- began to rise up in a portion of the crack that I had not previously seen . .”-Dionisio Pulido, 1943

Volcano Types: CINDER CONE

Volcano Types: DOME

Lassen Peak (USGS photo)

Volcano Types: SHIELD

Mauna Loa (USGS photo)

Volcano Types: Fissure Eruptions

Kilauea, USGS photo 1983

Volcano Types: COMPOSITE

Mt Rainier (NPS photo)

Volcano Types: CALDERA

Volcano Types: SUPERVOLCANOES

Volcano Types: SUPERVOLCANOES

5 Misconceptions about YELLOWSTONE

1) When Yellowstone erupts, it will be a catastrophe.

2) The magma chamber is growing.3) It’s overdue for a SUPER eruption.4) The land is rapidly rising.5) Earthquakes mean moving magma.

https://volcanoes.usgs.gov/volcanoes/yellowstone/faqs_misconceptions.html

But… What IF?!

Check out the docu-drama “Supervolcano” by BBC

and the Discovery Channel (2005)

• http://www.npr.org/2013/09/13/222101240/worlds-largest-volcano-discovered-on-pacific-seafloor (5.5 minutes) 13

Largest Volcano!

Eruption Hazards

Which is most dangerous?

Volcanic Hazards: Volcanic Gas

• Mainly water vapor (H2O) and carbon dioxide (CO2)

• Also sulfur dioxide (SO2), hydrogen sulfide (H2S)

15

The Importance of Volcanic Outgassing…16

Lake Nyos Cameroon

• Aug 1986• ~1,700 people died from

CO2 asphyxiation

Volcanic Hazards: Lava Flows

18Photo from Reuters 2014

Oceanic CrustLow Silica content (MAFIC)

Continental CrustHigh Silica content (FELSIC)

1) Mafic

Pahoehoe – ropey, fast flowing

• Low viscosity = flows freely• Low amount of Silica (Si)• Very hot (>950°C or ~1700°F)• http://www.youtube.com/watch?v=eoPz5O6_-d0

1) Mafic

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

A’a’ – crumbly, slow flowing

2) Intermediate

• Higher viscosity = poor flow (erupts more explosively)

• More of Silica (Si)• Hot (>750°C or ~1400°F)

3) Felsic

• High viscosity = does not flow• High Silica (Si) content• “Cool” Temperature (>650°C or ~1200°F)

Lava Flows

• Typically less than 1km/hour on gentle terrain• Basaltic lavas tend to be faster:

– Fastest ever• 30-60 km/hr Hawaii (18 to 40 mph)• 8-75 km/hr Vesuvius (5 to 47 mph)

• Siliceous lavas are typically slower:– 10’s to 100’s of m/hr (<1 mph)

24http://volcanoes.usgs.gov/vhp/lava_flows.html

Hawaii Kilauea Volcano Lava Flow Destroys 1st House:https://www.youtube.com/watch?v=U-3B7vO3tRI

Pyroclastic Debris

25

Volcanic Ash & Tephra

26http://gallery.usgs.gov/videos/625#.VK3Y-c8tHIV

28

Pyroclastic Flow orNuee ardente

https://www.youtube.com/watch?v=LRv-qDFSgV4

Geology

in

Can this happen?

https://www.youtube.com/watch?v=vfIUYDjo8WM

1997

Pyroclastic flows

• High-density mixture of hot, dry rock

fragments and hot gases, maybe water

– Density

– Gravity

What is it REALLY like?http://www.youtube.com/watch?v=Cvjwt9nnwXY1:12 minutes

Destroys by direct impact Melt snow and ice to form lahars

Burns forest, crops and buildingsBuries sites with hot rock debris

Pyroclastic flows

• How fast? Speed depends on: gradient and size

– >80 km/hr; max 700km/h (450 mph)

• How hot?

– 200-1,000°C (1,830°F)

• How far?

– Gravity, most follow topography

– 8 km, max=10-20 km (12 mi)

http://www.arch.virginia.edu/struct/pompeii/pyroclastic-6.html

http://volcanoes.usgs.gov/

How bad?

• 1902 eruption of Mont PeléeMartinique, West Indies

• 4 mi to St. Pierre

– killing ~30,000 inhabitants

How recent?

The good news?

• Reinforced concrete shelters

• Occasional survivors

• Instant death

• Active volcanoes

Th

e b

ad

ne

ws?

• Determining Run Out distance?

– Run-out distance: ∆H/L = 2.03V-0.15

• L= run-out distance

• ∆H = change in elevation

• V = volume of pyroclastic flow

• Determining Maximum Potential Velocity?

– Max potential vel: v = 0.38∆h0.68

• v = velocity

• ∆h = change in elevation

The really bad news?

Doyle et al., 2011http://rspa.royalsocietypublishing.org/content/467/2129/1348

Will they really make it?

http://spikedmath.com/math-games/challenge-games/pyroclastic-flow.html

Photo by Robin Holcomb USGS

Lahar

40https://www.youtube.com/watch?v=kznwnpNTB6k

What comes out of a volcano? Or…What are volcanic hazards?

What is the worst volcanic hazard?

44

Deaths Volcano When Major Cause of Death

92,000 Tambora, Indonesia 1815 Starvation

36,417 Krakatau, Indonesia 1883 Tsunami

29,025 Mt. Pelee, Martinique 1902 Ash flows

25,000 Ruiz, Colombia 1985 Mudflows

14,300 Unzen, Japan 1792 Volcano collapse, tsunami

9,350 Laki, Iceland 1783 Starvation

5,110 Kelut, Indonesia 1919 Mudflows

4,011 Galunggung, Indonesia 1882 Mudflows

3,500 Vesuvius, Italy 1631 Mudflows, lava flows

3,360 Vesuvius, Italy 79 Ash flows and falls

2,957 Papandayan, Indonesia 1772 Ash flows

Long Term Volcanic Hazards: Global Cooling

46

Long Term Volcanic Hazards: Global Warming

Eruption Styles

VISCOSITY (Composition and Temperature) help determine how violently the molten material will erupt

http://libraryphoto.cr.usgs.gov/cgi-bin/show_picture.cgi?ID=ID.%20HVO%20140ct

Will it FLOW?

http://libraryphoto.cr.usgs.gov/cgi-bin/show_picture.cgi?ID=ID.%20CVO-A.%20%20%204ct

Will it BLOW?

Different eruptive styles!

Eruption Styles

Eruption Styles

1. Molten material viscosityViscosity depends ona) Temperatureb) Composition (amount of Si)

49

Oceanic Crust

(Low Silica

content)

Continental

Crust (High Silica

content)

Depends on:2. Gas Content

http://w3.salemstate.edu/~lhanson/gls110/images_GLS110/Cascades_images/VocanClasses.gif

http://science.uniserve.edu.au/school/virtexps/vftkiama/pheasant/gasholes.jpg

Eruption Styles

What type of lava would you associate with a violent eruption?

33%

33%

33%

30

A. AndesiteB. BasaltC. Rhyolite

Based on:– Volume of

erupted material

– Plume Height

52

Volcanic Explosivity Index (VEI)

Eruption Styles

What’s so good about volcanoes?


Fertile Land: Nutrients in soil: N, K, and more

55


Energyhttp://www.npr.org/templates/story/story.php?storyId=16780339


Economic Deposits• Bauxite,

Diamonds, Gold, Nickel

• Base Metals: Lead, Zinc, and Copper


Where are the volcanoes?

Lithospheric Plates

Where are the volcanoes?

Why are there volcanoes?

6262

6363

Why are there volcanoes? Hot Spots




• The USGS monitors US Volcanic Hazards: http://volcanoes.usgs.gov/

• There are over 160 US volcanoes that have erupted in the past 10,000 years

• http://volcanoes.usgs.gov/about/volcanoes/volcanolist.php

• 57 are Priority, including:– Mt Rainier, Mt St Helens in Washington– Kilauea, Mauna Loa in Hawaii– Others in California and Oregon 70

http://volcanoes.usgs.gov/index.html

NYT 1/12/2016The 40,000-mile Volcano

Vol

cano

es in

the

New

s

http://www.nytimes.com/2016/01/12/science/midocean-ridges-volcano-underwater.html

Vol

cano

es in

the

New

s

Olympus Mons, MARS (NASA photo)

Recent World News 3/3/2016Volcanic Activity TIPPED Mars

Tharsis dome

http://recentworldnews.org/news/science/649491/mars-mega-volcano-red-planet

7474

Volcanoes in Minnesota?!

75

Midcontinent rift – a divergent margin –started to form, then failed

75

But a long, long time ago……about 1.1 BILLION years ago…

7676

What’s left?

77

Lake Superior Agates

Vesicles

Amygdaloids

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Science of Natural Disasters-Week 2-Volcanoes - … of Natural Disasters: Volcanoes! ... Indonesia 1772 Ash flows. ... Science of Natural Disasters-Week 2-Volcanoes Author: