Provided to the METSAT Element of the Weather Intelligence flight, to help the analysts get a better understanding of volcanoes.

1. Volcano
A naturally occurring opening
in the surface of the Earth
through which molten,
gaseous, and solid material is
ejected.
~Encarta
EXPLORE
CHAPTERS
Introduction
Etymology
Plate Tectonics & Hotspots
Types of Volcanoes
Lava Composition
Lava Behavior
Types of Eruptions
Ring of Fire
2009 AFWA Issued volcano products
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2. IntroductionIntroduction
As a METSAT analyst, it is your job to explore
all available information tools to help
determine the location of a volcanic eruption
of ash and the extent of the height and
direction of where the ash will travel.
*It is important to note that while it is
important to observe where lava is flowing,
advisory products will only be issued
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3. HOME
Make note of everything that can eject from a volcano and think about how each
can impact the local population and aircraft flying near or through the eruption
cloud.
INTRODUCTION

4. EtymologyEtymology
• The word volcano is derived from the name of
Volcano, a volcanic island in the Aeolian
Islands of Italy whose name in turn originates
from Vulcan, the name of a god of fire in
Roman mythology.
• The study of volcanoes is called volcanology.
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5. Plate Tectonics & Hotspots
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Divergent plate
boundaries
Convergent plate
boundaries
Hotspots
The pulling apart
of plates, causing
molten rock to
come to the top of
the mantle.
Causes mainly
submarine
volcanic activity
and creates new
oceanic crust.
The collision of
plates, causing
Subduction or
one plate to
submerge
beneath the
other.
Located away
from tectonic
plates, over
mantle plumes
where pipes vent
magma.
Volcanoes formed
over hotspot go
dormant and new
ones are formed
when plates move
overhead.

6. Divergent Plate Boundaries
Most divergent plate boundaries are at the bottom of the
oceans, causing most of the volcanic activity to be submarine,
thus forming new seafloor.
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PLATE TECTONICS

7. Convergent Plate Boundaries
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When two plates (usually an oceanic and continental plate) collide, causing
the one plate to submerge under the other plate (called subducting). In the
case of oceanic-continental, a deep trench just off shore is formed.
When the viscous magma, high in silica content, reaches the surface, a
volcano is formed.
*This is what caused the typical Ring of Fire volcanoes.*
Oceanic - Oceanic convergenceContinental - Continental convergenceOceanic - Continental convergence
PLATE TECTONICS

8. How Plate Tectonics Work
1 – Lithosphere: Continental & Oceanic
2 – Asthenosphere
3 – Softened, dense rock flows slowly
4 – Convection currents bring hot material
up toward the surface
5 – Convection currents diverge at base of
lithosphere; pulls on the solid plate. Tension
causes solid plate to break apart (divergent
plate boundary)
6 – Space fills with molten rock (magma).
Seawater cools magma and solidifies,
forming new oceanic lithosphere. Over time
mid-ocean ridge gets larger.
7 - The older part of plate moves away from
the ridge, where the new lithosphere has
been added.
8 – The further away the plate moves from
the spreading ridge, it cools. The colder the
plate, the heavier it becomes. The furthest
edge from the ridge becomes denser than
asthenosphere beneath it.
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PLATE TECTONICS

9. How Plate Tectonics Work
Cont’d
9 – The dense plate sinks beneath another,
causing a subduction zone to form.
10 – The sinking edge pulls the rest of the
plate behind it.
11 – Subduction zones are a form of
convergent plate boundary. The less dense
continental plate floats above the more
dense asthenosphere.
12 – Extreme heat and pressure at depth of
the subducting plate cause fluids to sweat,
which percolate upward and melts overlying
solid mantle above the plate to form pockets
of magma.
13 – The new magma is less dense than
surrounding rock and rises toward surface. It
cools and solidifies as large intrusive rocks.
When exposed by erosion, forms the cores
of great mountain ranges (i.e. Sierra Nevada
& Andes)
14 – Some molten rock reaches Earth’s
surface to erupt , forming volcanic rocks.
Accumulation of layers over time construct
volcanic mountain ranges (i.e. Cascade
range)
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PLATE TECTONICS

10. Hotspots
Located over a mantle plume, where
the convection of the Earth’s mantle
creates a column of hot material that
rises until it reaches the crust. Pipes
form in the crust, which vents
magma.
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PLATE TECTONICS

11. Ring of Fire
Result of plate tectonics and the movement and collisions of crustal plates.
Area where large numbers of earthquakes and volcanic eruptions occur in a 40,000km
horseshoe shape. Associated with a nearly continuous series of activity.
Contains 452 volcanoes, with over 75% of worlds active and dormant volcanoes.
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PLATE TECTONICS

12. 4 Main Types of Volcanoes4 Main Types of Volcanoes
Cinder Cones (Volcanic cones)
Composite volcanoes
(Stratovolcanoes)
Shield Volcanoes
Lava domes
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13. Shield Volcanoes
• Named for their broad,
shield-like profiles.
• Formed by the eruption of
low-viscosity lava that can
flow a great distance from a
vent, but usually not a
catastrophic explosion.
• Gradual buildup and near
continuous characteristics.
• More common in oceanic
settings.
VOLCANO TYPES
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14. Lava Domes
• Formed by small, bulbous
masses of lava too
viscous to flow a great
distance.
• Lava piles over and
around its vent, and the
dome grows by expansion
within.
• Commonly found within
craters or on flanks of
large composite
volcanoes.
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VOLCANO TYPES

15. Volcanic (Cinder) Cones
• Built from particles of
congealed lava ejected from
a single vent.
• Gas-charged lava blows
violently into the air, breaks
into small fragments and
fall once solid as cinders
around the vent.
• Most have a bowl-shaped
crater at the summit, and
rarely rise more than 1K
feet above surroundings.
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VOLCANO TYPES

16. Stratovolcanoes (Composites)
• Steep-sided,
symmetrical cones.
Formed by alternating
layers of lava flows,
volcanic ash, cinders,
blocks, and bombs.
• May rise 8K or more
feet above
surroundings.
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VOLCANO TYPES

17. Supervolcanoes
• Occurs when magma in the
Earth rises into the crust
from a hotspot but cannot
break through the crust.
Pressure builds until the
crust can no longer contain
it.
• Can produce devastation on
an enormous scale.
• Most dangerous kind and
can cool global
temperatures for years
after eruptions due to the
volume of sulfur and ash.
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VOLCANO TYPES

18. Submarine volcanoes
• Located on the ocean floor.
• Active ones in shallow
water may shoot steam and
rocky debris into the air.
• Deep eruptions may be
prevented by the weight of
the water.
• Rapid cooling by the water
causes the erupted
materials to solidify, often
creating pillow lava.
• That is how many islands
were developed.
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VOLCANO TYPES

19. Subglacial volcanoes
(glaciovolcano)
• Develop under icecaps.
• During an eruption, the
heat of the lava melts
the overlying ice. The
water cools the lava,
creating pillow lava
shapes.
• Most common in
Iceland & Antarctica
and have a flat top with
steep sides.
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VOLCANO TYPES

20. Lava CompositionLava Composition
Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Magnesium (Mg)
Titanium (Ti)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Phosphorous (P)
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10 elements make up most magmas:
O & Si are the two most abundant elements in magma and are therefore described
by silica content (SiO2). Click on the types of lava below for more information on
each.

21. Felsic
• High percentage of silica
(>63%)
• Highly viscous
• Erupted as domes or short,
stubby flows.
• Typically forms
stratovolcanoes or lava domes.
• The viscosity traps gases,
which cause more catastrophic
eruptions .
• Spurs pyroclastic flows and
leaves thick layers of deposits,
sometimes several meters
deep.
LAVA COMPOSITION
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22. Pyroclastic flows
• Temperatures as high
as 1,200 ⁰C
• Will incinerate anything
flammable in their path,
while leaving a thick
layer of pyroclastic flow
deposit.
LAVA COMPOSITION
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23. Andesitic
• Lower in aluminum and silica, usually richer in magnesium
and iron.
• Form andesite domes and block lavas.
• Temperatures between 750 and 950 ⁰C and are less viscous.
LAVA COMPOSITION
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24. Mafic
• Erupt at
temperatures above
950 ⁰C.
• High in iron and
magnesium, with
lower aluminum and
silica.
• Low viscosities.
• Typically forms low-
profile shield
volcanoes.
LAVA COMPOSITION
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25. Lava BehaviorLava Behavior
Highly viscous
• Flows slowly, clogs, and
forms semi-solid blocks
which resist flow.
• Tends to entrap gas, which
forms bubbles within the
rock.
• Correlates to explosive
eruptions and is associated
with pyroclastic flows.
Low viscous
• Tends to flow easily,
forming puddles, channels
and rivers of molten rock.
• Tends to easily release
bubbling gases as they’re
formed.
• Rarely pyroclastic.
• Tend to form broad shields
rather than steep cones.
Viscosity of lava determines how the lava will behave.
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26. Types of EruptionsTypes of Eruptions
Non-explosive
• Flood lavas
• Hawaiian style
• Mid-ocean ridges
Explosive
• Strombolian
• Vulcanian
• Surtseyan
• Vesuvian/Plinian
• Peléan
• Bandaian
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27. Non-explosive
• Flood lavas: basaltic & can be highly
voluminous
• Hawaiian style: with some tephra and fast-
moving fluid lavas; often channelized.
• Mid-ocean ridges: largely restricted to
spreading center rifts as small cones and sheet
flows.
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ERUPTION TYPES

28. Explosive  Strombolian
• Low-level eruptions, consists of ejection of
incandescent cinder, lapilli and lava bombs to
altitudes of tens to hundreds of meters.
• Small to medium in volume, with sporadic violence.
1 – Ash plume
2 – Lapilli
3 – Volcanic ash rain
4 – Lava fountain
5 – Volcanic bomb
6 – Lava flow
7 – Layers of lava and ash
8 – Stratum
9 – Dike
10 – Magma conduit
11 – Magma chamber
12 - Dike
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ERUPTION TYPES

29. Explosive  Vulcanian
• Eruption characterized by a dense cloud of ash-laden
gas exploding from the crater and rising high above
the peak.
• Increased silica content of magma (which has
increased viscosity) means increased explosiveness.
1 – Ash plume
2 – Lapilli
3 – Lava fountain
4 – Volcanic ash rain
5 – Volcanic bomb
6 – Lava flow
7 – Layers of lava and ash
8 – Stratum
9 – Sill
10 – Magma conduit
11 – Magma chamber
12 - Dike Sakurajima, Japan
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ERUPTION TYPES

30. Explosive  Surtseyan
• Takes place in shallow seas or lakes.
• Commonly phreatomagmatic (a result of interaction
between water and magma) representing violent
explosions.
1 – Water vapor cloud
2 – Cupressoid ash
3 – Crater
4 – Water
5 – Layers of lava and ash
6 – Stratum
7 – Magma conduit
8 – Magma chamber
9 – Dike
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ERUPTION TYPES

31. Explosive  Vesuvian/Plinian
• Displays as columns of gas and volcanic ash extending
high into the stratosphere and eject large amounts of
pumice.
• Can last less than a day to months. May collapse top of
volcano, resulting in a caldera, and fine ash will deposit
over large areas.
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Redoubt
ERUPTION TYPES

32. Explosive  Peléan
• Characteristics include presence of a glowing
avalanche of hot volcanic ash and formation of lava
domes, short flows of ash or the creation of pumice
cones.
• Collapse of ash columns.
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1 – Ash plume
2 – Volcanic ash rain
3 – Lava dome
4 – Volcanic bomb
5 – Pyroclastic flow
6 – Layers of lava and ash
7 – Strata
8 – Magma conduit
9 – Magma chamber
10 – Dike
ERUPTION TYPES

33. Classification of volcanoes
• Volcanoes that
erupt regularly.
• Actual lifespan can
last from months
to several million
years.
Dormant
• Volcanoes that have
erupted in historical
times, but now quiet.
• Considered when
eruptions have been
historically many
(possibly thousands
or more) years apart
and could erupt
again. (Pompeii and
previously Soufriere
Hills)
Active Extinct
• Volcanoes that
have not erupted
in recorded
historical times
• Scientists consider
them to be
unlikely to erupt
again because
there is no longer
a lava supply.
ERUPTION TYPES
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34. 2009 AFWA Issued2009 AFWA Issued
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