The Science of Prediction
Monitoring Volcanic Activity
www.unavco.org/cws/modules/cws/modules/yellowstone/
Signs of Volcanic Activity
Scientists look for five signs that volcanic processes
are at work
• Eruption History
• Volcanic Gases
• Heat and Hydrothermal Activity
• Earthquake activity
• 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/
Monitoring
• These tools usually use radio signals to transmit data
to a field office or “Volcano Observatory”
• There are five volcano observatories in the US
operated by partnerships between the USGS and
other organizations
 Alaska (AVO)
 Hawaii (HVO)
 Cascades WA (CVO)
 Long Valley CA (LVO)
 Yellowstone MT (YVO)
Monitoring
• Mt. St. Helens in
Washington state
erupted May 18th
1980
• Scientists were able
to save many lives by
closely monitoring
the warning signs
that predicted an
upcoming eruption
• By April 1980, Mt. St.
Helens was covered
with monitoring
equipment
Image from Smithsonian National Museum of Natural History (n.d.) Global Volcanism Program: St. Helens Index of Monthly
Reports http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05-&volpage=var#sean_0509
Eruptions
• “The Past is the Key to the
Present” Scientists can learn a
lot about how a volcano erupts
by looking at it’s past eruptions
• Ash, gas and steam eruptions
 Occur when hot, pressurized,
trapped gases or steam escape
 Usually detected by surface
earthquakes, elevated volcanic
gas levels and visual plumes
 Before erupting May 1980, Mt.
St. Helens had many gas and
steam eruptions
 Since 1980, Mt. St. Helens has
continued to have periodic steam
eruptions
Image from Haselhorst, C (1980) Yellowstone Digital
Slide File “Volcanics, Igneous”
http://www.nps.gov/archive/yell/slidefile/geology/volca
nicsigneous/Page-4.htm
Eruptions
• Lava flows
 Occur when magma rises to the surface and “leaks” out of
cracks/fissures or vents
 Usually detected by shallow earthquakes followed by
elevated gas levels and heat measurements
 In September 2004 Mt. St. Helens began erupting lava into
its crater slowly building a dome
Image from Yellowstone Digital Slide File “Volcanics,
Igneous”
http://www.nps.gov/archive/yell/slidefile/geology/volca
nicsigneous/Page-8.htm
Eruptions
• Pyroclastic flows
 Occur when superheated gases “flow”
down the flanks of a volcano
 Can be preceded by earthquakes and
elevated gas levels however Mt. St.
Helens’ pyroclastic flow was initiated
by a landslide
 On May 18th 1980, Mt. St. Helens
devastated the local ecology when a
pyroclastic flow descended the north
flank, destroying everything in its path
• Hydrothermal explosions
 Occur when superheated, pressurized
and trapped steam escapes blowing a
crater in the ground
 May happen even when magma is not
rising
Image from Yellowstone Digital Slide File “Volcanics,
Igneous”
http://www.nps.gov/archive/yell/slidefile/geology/volca
nicsigneous/Page-3.htm
Volcanic Gases
• Gases dissolved in magma
provide the energy for volcanic
eruptions
• Volcanic gases are the result of
chemical reactions and physical
changes in the magma as it rises
and cools
• Gases can be released as magma
rises, as it erupts to the surface
and even as magma cools below
the surface
• THE PRIMARY GAS IN AN
ERUPTION IS WATER VAPOR!
Image from Driedger, C., Doherty, A., and Dixon, C. (Project Coordinators),
2005, Living with a Volcano in your Backyard -- An Educator's Guide with
Emphasis on Mount Rainier: U.S. Geological Survey and National Park Service,
General Interest Publication 19.
http://vulcan.wr.usgs.gov/Outreach/Publications/GIP19/framework.html
Volcanic Gases
• Volcanic gases often get trapped underground
where pressure builds up causing pyroclastic,
steam or ash eruptions or hydrothermal
explosions
• Monitored gases include
Carbon dioxide
Sulfur dioxide
Hydrogen sulfide
Image by S.R. Brantley accessed 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
Post 1980 Steam plume
from Mt. St. Helens
Volcanic Gases
• Volcanic gases are hard to sample and
measure because they are found in hazardous
places and are toxic to living things
• Volcanic gases are detected using
Spectrometers on the ground or mounted on an
airplane
Samples collected by hand and analyzing in a
laboratory
A scientist collects gas
samples for analysis. Notice
the protective equipment that
he is wearing.
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
Volcanic Gases
• Scientists look for
changes to living things
such as trees and animals
to detect and trace
emissions of gases
• Trees and animals can be
effected by gasses
• These trees at Mammoth
Mountain, CA died when
carbon dioxide 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/
Volcanic Gases
• Following Mt. St. Helen’s eruption in 1980, Sulfur
dioxide levels fell dramatically
Notice that the vertical scale is in TONS per DAY!
AFTER the May 18th eruption, Mt. St. Helens still
released nearly 500,000 metric tons of sulfur dioxide
gas into the atmosphere
Image from USGS (2002) Volcano Hazards
Program: Strategy for reducing volcanic risk
“SO2 gas emission rates of Mount St.
Helens, 1980-1988
http://volcanoes.usgs.gov/About/What/Monit
or/Gas/MSH1980-88.html
Heat and Hydrothermal Activity
1. Water from precipitation and snowmelt seeps into the ground by
following fractures and cracks in the
bedrock.
2. This water is then warmed by heat
(800 degrees C or more) from the
magma chamber or hot rock causing
it to rise back to the surface.
1
4
5
3. As heated water rises, the pressure
from rocks above decreases and the
liquid expands.
4. If this expanded water gets trapped
then it becomes pressurized by
gases and may lead to geysers,
steam eruptions or hydrothermal
explosions.
5. If the gas is allowed to escape then
the heated water bubbles to the
surface as a hot spring or bubbling
mudpot
3
2
Image from Clynne, M., Janik, C., and Muffler, L. (n.d.) “Hot Water” in Lassen
Volcanic National Park— Fumaroles, Steaming Ground, and Boiling Mudpots.”
USGS Fact Sheet 101-02
pubs.usgs.gov/fs/2002/fs101-02/
Heat and Hydrothermal Activity
FLIR image of Mt. St. Helens’
new dome June 26th 2007
• Hydrothermal Activity
results from a magmatic
heat source, so it
demonstrates the
presence of magma, not
necessarily that the
magma is moving to the
surface
• Thermal features can be
monitored by
Image from (2007) USGS Mount St.
Helens, Washington Forward Looking
Infrared Images
http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/M
SH07/MSH07_area_new_growth_on_dom
e_06-26-07_FLIR_med.jpg
 Night time aerial
observations
 Thermal Infrared imaging:
FLIR (Forward Looking
Infrared) thermal imaging
- photographs of features
in infrared wavelengths of
light
 Direct temperature
measurements
Earthquakes
• Moving magma and volcanic fluids cause earthquakes
• Earthquake activity always increases before an eruption
because liquid magma, hot fluids, and gases are less dense
than the surrounding rocks so they force their way through
the crust to reach the surface.
• Most volcanic earthquakes are:
• <3 Magnitude
• Shallower than 10 km
• Occur in swarms (lots of earthquakes, close together)
Magma rises into
reservoir
beneath volcano
Rising magma
and volcanic
gases exert
pressure
High pressure
causes rocks to
break, triggering
earthquakes
Image from USGS
Volcano Hazards
Program “Monitoring
Volcano Seismicity.”
http://volcanoes.usgs.go
v/activity/methods/seism
ic/index.php
Earthquakes
• Earthquakes are measured by
seismometers that detect
ground vibrations
• Different sources of vibrations
cause different patterns on a
seismometer
• Scientists can detect magma on
the move by looking for the
pattern of magmatic
earthquakes called volcanic
tremors (VT’s)
Seismographs record seismic signatures,
Mount Pinatubo, Philippines
Image from USGS Volcano
Hazards Program “Monitoring
Volcano Seismicity.”
http://volcanoes.usgs.gov/acti
vity/methods/seismic/signatur
es.php
Earthquakes
• Scientists can tell where Mt. St. Helens’ magma source
is by looking at it’s pattern of earthquakes (many
earthquakes occurring close together)
Earthquakes
Image from Smithsonian National Museum
of Natural History (n.d.) Global Volcanism
Program: St. Helens Index of Monthly
Reports
http://www.volcano.si.edu/world/volcano.cf
m?vnum=1201-05&volpage=var#sean_0509
• Between March 1980
and May 1980 an
average of 10
magnitude >3.5
earthquakes were
recorded per day at
Mt. St. Helens
• Swarms of hundreds of
smaller earthquakes
occurred daily
• Earthquakes continue
to be common at Mt.
St. Helens since dome
rebuilding began in
2004
Ground Deformation
• Volcanoes change shape before,
during, and after eruptions
• Volcanoes inflate (bulge) and
deflate (sink)
Upward pressure from rising
magma
Illustration by
B. Myers and S. Brantley
• Deformation is caused by trapped
and pressurized gases or fluids.
• Deformation can be detected by
monitoring gas emissions
• Deformation can also be a sign of
rising magma
• Usually accompanied by swarms of
shallow earthquakes
Image from USGS Volcano
Hazards Program “Monitoring
Volcano Seismicity”.
http://volcanoes.usgs.gov/acti
vity/methods/seismic/index.ph
p
Ground Deformation
• Deformation is measured using
Tiltmeters which work like a
carpenter’s level and can be
left in place
Global Positioning System
which uses satellites to
triangulate the position of a
GPS receiver unit
Leveling Survey where
scientists use survey
equipment to measure
position and then return
periodically to make
additional measurements
Tiltmeter site on crater floor of Mount St. Helens
Photograph by S.R. Brantley on 9 June 1982
GPS site on
Augustine Volcano,
Alaska
Image from USGS Volcano
Hazards Program “Monitoring
Volcanic Ground
Deformation.”
http://volcanoes.usgs.gov/acti
vity/methods/deformation/ind
ex.php
Ground Deformation
• Between March 1980
and May 1980, Mt. St.
Helens’ north flank
bulged up to 60 meters
• This deformation lead to
the huge landslide that
induced the pyroclastic
flow, volcanic mudflow
and ash eruption on
May 18th 1980
Image from Smithsonian National Museum
of Natural History (n.d.) Global Volcanism
Program: St. Helens Index of Monthly
Reports
http://www.volcano.si.edu/world/volcano.cf
m?vnum=1201-05&volpage=var#sean_0509
The 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. Four-tiered Volcano Alert Levels
NORMAL
Volcano is in typical background, noneruptive
state
or, after a change from a higher level, volcanic
activity has ceased and volcano has returned to
noneruptive background state.
ADVISORY
Volcano is exhibiting signs of elevated
unrest above known background level
or, after a change from a higher level,
volcanic activity has decreased
significantly but continues to be closely
monitored for possible renewed increase.
WATCH
Volcano is exhibiting heightened or
escalating unrest with increased potential
of eruption, timeframe uncertain,
OR eruption is underway but poses limited
hazards.
WARNING
Hazardous eruption is imminent,
underway, or suspected.
Table from USGS Volcano Hazards Program “USGS Volcanic
Activity Alert-Notification System”
http://volcanoes.usgs.gov/activity/alertsystem/
Sources
•
Driedger, C., Doherty, A., and Dixon, C. (Project Coordinators), (2005), “Living with a Volcano in your Backyard -- An
Educator's Guide with Emphasis on Mount Rainier”. U.S. Geological Survey and National Park Service, General Interest
Publication 19. http://vulcan.wr.usgs.gov/Outreach/Publications/GIP19/framework.html
•
Smithsonian National Museum of Natural History (n.d.) Global Volcanism Program: St. Helens Index of Monthly Reports
http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05-&volpage=var#sean_0509
•
USGS (2007) Volcano and Hydrologic Monitoring Techniques
http://vulcan.wr.usgs.gov/Monitoring/techniques.html#seismic_monitoring
•
USGS (2002) Volcano Hazards Program: Strategy for reducing volcanic risk http://volcanoes.usgs.gov/
•
USGS (2004) Tracking Changes in Yellowstone's Restless Volcanic System http://pubs.usgs.gov/fs/fs100-03/