Part 4: Volcanic Hazards & MonitoringPart 4: Volcanic Hazards & Monitoring

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Slide show prepared by Slide show prepared by Dr. Beth Pratt-Sitaula (Central Washington University) and Jenda Johnson (IRIS).Dr. Beth Pratt-Sitaula (Central Washington University) and Jenda Johnson (IRIS).

Volcanoes are…

An opening on the planet’s surface where molten rock, ash, or gases escape from below

Aleutian Islands, AK; International Space Station photo

http://earthquake.usgs.gov/monitoring/anss/regions/hi/

1. Volcanoes are steep-sided and ooze hot runny lava

FALSE FALSE - - ““Hot runnyHot runny”” volcanoes are volcanoes are mostly flat or shield likemostly flat or shield like

Volcano Prior Knowledge SurveyVolcano Prior Knowledge Survey

TRUE/FALSE –> thumbs up OR downTRUE/FALSE –> thumbs up OR down

http://www.imdb.com/media/rm1327600128/tt0445548

Volcano Prior Knowledge SurveyVolcano Prior Knowledge Survey

2. The biggest eruptions flatten topography.

TRUE TRUE – – largest volumelargest volume eruptions eruptions lead to flood basalt plateaus; lead to flood basalt plateaus; most explosivemost explosive eruptions lead to eruptions lead to mountains getting blown to bitsmountains getting blown to bits

TRUE/FALSE –> thumbs up OR downTRUE/FALSE –> thumbs up OR down

http://www.imdb.com/media/rm1327600128/tt0445548

Volcano Prior Knowledge SurveyVolcano Prior Knowledge Survey

3. Magma chambers are…big chambers of liquid rock

FALSE - Magma FALSE - Magma ““chamberschambers”” form form when lava is injected in cracks and when lava is injected in cracks and crevasses and pushes against crevasses and pushes against existing rock. They are usually existing rock. They are usually more of a plumbing system than a more of a plumbing system than a chamber.chamber.

TRUE/FALSE –> thumbs up OR downTRUE/FALSE –> thumbs up OR down

SHOW ANIMATION “Mesozoic Subduction” from URL below.http://emvc.geol.ucsb.edu/2_infopgs/IP1GTect/cSubduction.html

• How many active volcanoes on Earth?

• How many volcanoes erupt per year?

• How many people are killed by volcanoes?

~1,500 active volcanoes~1,500 active volcanoes

~60 volcanoes erupt per year~60 volcanoes erupt per year

~200,000 in the last 200 years~200,000 in the last 200 years

Some volcano statsSome volcano stats

Where does molten rock come from?

Modified from USGS Graphics

Where do volcanoes form?

• Subduction zones

• “Hot spots”

• Mid-ocean ridges

• Continental rift zones

Rocks melt under certain circumstances

1. Heating

2. Decompression

3. Reducing melting temp by adding water

Types of Volcanoes

Flood Basalts

Millions km3 of horizontal

basalt layers

Columbia Flood Basalts Photo by Thor Thordarsson

Why do different magmas behave differently & make very different volcanoes?

• VISCOSITY

• VOLATILES

• VOLUME

“3 Vs” •WATER

•CARBON DIOXIDE

•Sulfur dioxide

•Hydrogen sulfide

Viscosity determines:

1. The flow rate of magma

2. VOLATILE trapping

vs

Viscosity depends on chemical composition

http://volcanoes.usgs.gov/images/pglossary/VolRocks.php

Types of Volcanoes

Flood Basalts

Millions km3 of horizontal

basalt layers

Columbia Flood Basalts Photo by Thor Thordarsson

Flood basalts

• Extremely low viscosity

• Few volatiles (non-explosive)

• Very very large volume

http://www.fas.org/irp/imint/docs/rst/Sect17/Sect17_3.html

Flood basalts - HAZARDS

• Bury your state in lava

• Huge green house gas release

• Geologic ennui (if you find basalt dull)

http://www.fas.org/irp/imint/docs/rst/Sect17/Sect17_3.html

Columbia River Flood Basalts

• Over 300 separate flows averaging 580 km3 EACH• 3.5 km thick in places• Erupted 17.5-6 Ma• ~90% erupted 16-15 Ma http://geosphere.gsapubs.org/content/4/3/480.full.pdf+html

Thor Thordarsson

Shield Volcanoes

• Low viscosity

• Few volatiles (non-explosive)

• Large volume

Mauna Loa, Hawaii USGS

Shield Volcanoes - HAZARDS

• Lava flows

• Volcanic gasses (esp. CO2)

Medicine Lake Volcano, CA USGS

Cinder cone (or scoria cone)

• Moderate viscosity

• Some volatiles

• Small volume

Image released to public domain by Q Myers (English Wikipedia)

~600 m

Lava Butte, OR

Stratovolcano

• Mod–high viscosity

• Few-many volatiles (mod-very explosive)

• Mod-large volume

Mt Rainier and Seattle, WA

&

Stratovolcano – multiple types of eruption processes

Lava dome

Ash cloud

Pyroclastic flows

USGS Mt. St. Helens, 1984

USGS Mt Mayon, Philippines, 2006

http://www.tulane.edu/~sanelson/geol111/igneous.htm

Stratovolcano - Mt St Helens

Before 1980 eruptionbuilt up

USGS

USGS

After 1980 eruptionblown to bits

Stratovolcano - HAZARDS• Pretty much all types of volcanic hazards

USGS

Stratovolcanoes – PACIFIC NW

Most Cascade volcanoes are stratovolcanoes (typical for subduction zones)

Stratovolcano

shield vs composite

Mauna Loa’s full height = 19,000 ft + 13,000 ft = 32,000 ft

below sea level

above sea level

Mt Rainer = 14,400 ft

Caldera formation

Magma chamber partially emptied during eruption

Center collapses down and forces out more magma

Caldera is formed

Coke w/dry ice

• High viscosity• Many volatiles (very explosive)• Large volume

http://pubs.usgs.gov/fs/2002/fs092-02/

Caldera formation - HAZARDS• Ash falls• Pyroclastic flows• Volcanic landslides• Volcanic gasses

http://pubs.usgs.gov/fs/2002/fs092-02/

Crater Lake Caldera, OR

Continental Hotspot CalderaYellowstone, WY

http://pubs.usgs.gov/fs/fs100-03/

Yellowstone Eruptions

http://www.nps.gov/yell/naturescience/eruptions.htm

http://pubs.usgs.gov/fs/2005/3024/

Snake River Plain, IdahoPossible Hot Spot Trail from SW to NE over last 16 Ma

16 Ma

10 Ma

5 Ma 2 Ma1.3 Ma

0.6 Ma

ID

UT

WY

NV

OR

Image after Smith & Siegel (2000), Windows into the Earth: the Geological Story of Yellowstone and Grand Teton National Parks

80 km

Proposed relationship between flood basalts & hotspots

Columbia Flood Basalts

Yellowstone hotspot track~16 Ma

Cascade Volcanoes

Show real roll-over

Below Cascade volcanoes

Major rock types

CLASSIFICATION OF INTRUSIVE ROCKS

Gabbro Diorite Granodiorite Granite

Volcanic Hazards

• Pyroclastic flow (a.k.a. ash flow)

• Lahar (a.k.a. mud flow or debris flow)

• Gases

• Ash falls

• Volcanic Landslides

• Lava Flows

• Tsunamis USGS

Show Understanding Volcanic Hazards clips

Mt Rainier Lahar Hazard

Ash fall hazard

USGS

The Science of PredictionMonitoring Volcanic Activity

Signs of Volcanic Activity

Scientists look for five signs that volcanic processes are at work

• Eruption History

• Volcanic Gases

• Heat and Hydrothermal Activity

• Earthquakes

• Ground deformation

Monitoring

Scientists use many tools to monitor volcanoes

Since erupting volcanoes are dangerous, they prefer tools that can be set up and left

Image from USGS (2002) Volcano Hazards Program: Strategy for reducing volcanic risk http://volcanoes.usgs.gov/

Volcanic Gases

Volcanic gases are hazardous and hard to sample – they can be detected using :

• Spectrometers mounted on ground or airplane

• Samples collected by hand and analyzing in a laboratory

Image from USGS Volcano Hazards Program “Measuring volcanic gases: emission rates of sulfur dioxide and carbon dioxide in volcanic plumes.” http://volcanoes.usgs.gov/About/What/Monitor/Gas/plumes.html

A scientist collects gas samples (Note the protective equipment)

Volcanic Gases

• Trees and animals can be effected by gasses and aid detection

• Trees at Mammoth Mt, CA died when CO2 suffocated their roots

Image from USGS Fact Sheet 172-96 “Invisible CO2 Gas Killing Trees at Mammoth Mountain, California” http://pubs.usgs.gov/fs/fs172-96/

Heat & Hydrothermal Activity

Hydrothermal activity demonstrates presence of magma, not necessarily magma movement

Thermal features can be monitored by:• Night aerial observations

• Thermal (infrared) imaging

• Direct temperature measurements

Image from (2007) USGS Mount St. Helens, Washington Forward Looking Infrared Images http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/MSH07/MSH07_area_new_growth_on_dome_06-26-07_FLIR_med.jpg

Infrared image of Mt. St. Helens’ new lava

dome June 26th 2007

Earthquakes

• Moving magma and volcanic fluids cause quakes

• Most volcanic earthquakes are:• <3 Magnitude• Shallower than 10 km• Occur in swarms

Magma risesMagma and gases exert pressure

Rocks break, triggering earthquakes

Image from USGS Volcano Hazards Program “Monitoring Volcano Seismicity.” http://volcanoes.usgs.gov/activity/methods/seismic/index.php

Earthquakes

Scientists can tell where Mt. St. Helens’ magma source is by looking at earthquake pattern.

Ground Deformation

• Volcanoes change shape before, during, and after eruptions

• Deformation is caused by trapped and pressurized gases or fluids (monitor gas emissions too!)

• Usually accompanied by swarms of shallow earthquakes (monitor seismicity too!)

Image from USGS Volcano Hazards Program “Monitoring Volcano Seismicity.” http://volcanoes.usgs.gov/activity/methods/seismic/index.php

Ground Deformation

Deformation is measured using:

•Tiltmeters (big, underground carpenter’s level)

•Global Positioning System (satellites triangulate position)

•Leveling Survey (periodic repeat measurements)

GPS site Augustine Volcano, Alaska

Mt St Helens image from USGS Volcano Hazards Program “Monitoring Volcano Ground Deformation.” http://volcanoes.usgs.gov/activity/methods/deformation/tilt/msh.php

Tiltmeter at Mt St Helens’ crater floor

Science of Prediction

Even though scientists could not predict the exact moment when Mt. St. Helens would erupt, they were able to save many lives by predicting that it would erupt.

Table 1. SUMMARY OF VOLCANIC-ALERT LEVELS

NORMAL Typical background activity of a volcano in a non-eruptive state After a change from a higher level: Volcanic activity considered to have ceased, and volcano reverted to its normal, non- eruptive state.

ADVISORY Elevated unrest above known background

activity After a change from a higher level: Volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCH Heightened/escalating unrest with increased potential for eruptive activity (timeframe variable) OR a minor eruption underway that poses limited hazards

WARNING Highly hazardous eruption underway or imminent

Table from USGS Volcano Hazards Program “USGS Volcanic Activity Alert – Notification System” http://volcanoes.usgs.gov/activity/alertsystem/

Volcanic monitoring animations by

http://www.iris.edu/hq/programs/education_and_outreach/animations#CC

Mt St Helens erupted a lava dome 2004-2008

What direction did the GPS stations move during this eruption?

– Outwards?

– Inwards?

http://vulcan.wr.usgs.gov/Volcanoes/MSH/Eruption04/Monitoring/February2008/

Mt St Helens GPS data 2004-5

Lisowski et al, UNAVCO proposal, 2008