Volcanoes
Liquid Hot Magma.
Tungerahua Volcano, Ecuador
Picture by Alcinoe Calahorrano
Volcano Stats
• Definition of Volcano
– Mountain that forms when molten rock
(magma) is forced to the Earth’s surface
• Number of active volcanos = ?
– 20 erupting right now
(50-60/year) (160/decade)
• Number of volcanologists = 1,500
Lava flow
Volcanic Eruptions
• Nonexplosive Eruptions
Lava fountain
• Explosive Eruptions
What is Lava?
-magma that flows onto
the Earth’s surface
1. What did you learn?
Write/draw this in your
science journal.
Volcanoes
form around
Vents
Lava
vents that
release magma
onto the Earth’s
surface.
Magma chamber
The Composition of Magma Determines
whether it is explosive or not!
• High water content
– More likely to be
• High
!!!
content
– More likely to be
– Why?
!!!
• Silica has a thick, stiff consistency
– Flows slowly
– Tends to Harden in the volcano’s vent
2. What did you learn?
Write/draw this in your
science journal.
a. What physical event causes explosive
eruptions?
b. Would high water content increase the
likelihood of having an explosive eruption?
c. Would high silica content increase the
likelihood of having an explosive eruption?
What Erupts from a
Volcano?
Blocky lava
Lava can be
thick or thin.
Pahoehoe
Aa
Pillow lava
1. Loosen the gelatin volcano from the cups by dipping the cups briefly
in the bowl of hot water.
2. Lay the pegboard on top of a food serving tray to collect drips.
3. Weave the airline tubing into the pegboard from the top and back up
through the bottom so that 2” or so of tubing is sticking up out of the
pegboard. Remove the plunger.
4. Fill the syringe with your prepared “magma.” Remove any air
bubbles from the syringe and tubing by holding the syringe upright
and squirting out a small amount of the liquid. Air tends to fracture
the gelatin.
5. Unmold the gelatin by tipping the bowl over onto the center of the
pegboard on top of the tubing and lifting the bowl. Do this VERY
CAREFULLY so that the gelatin cast won’t develop cracks; a few
small cracks are acceptable. The gelatin cast will spread and settle.
It should resemble a colorless to milky volcano.
6. Inject the red water VERY SLOWLY, at a rate of about 20 ml/min.
Each student should inject about 10mL into the volcano with the
other students watching carefully.
7. What do you observe?
8. Use a plastic knife to slice open the volcano, and view the crosssection.
3. What did you learn?
Write/draw this in your
science journal.
a. Where did the lava flow in your model?
b. Did the lava choose the path of least
resistance (weakest places), like cracks?
c. Did the lava deepen the existing cracks or
make new cracks?
What Erupts from a Volcano?
Pyroclastic material
• Rock fragments created by
eruptions
•magma explodes from volcano and solidifies in the air
•existing rock is shattered by powerful eruptions
Lapilli
Volcanic bombs
Volcanic blocks
Volcanic ash
How do volcanoes affect the Earth?
Flows and Fallouts
• hot ash can flow really
quickly
•Knock down buildings
•Dam rivers (flooding/drought)
•Kill crops and livestock
Climatic Changes
•Ash & Gases can block sunlight
•Drop average global temperature
noticeably
Types of Volcanoes
Shield volcano
Cinder cone volcano
Composite volcano
Craters, Calderas, and Lava
Plateau
Crater
• From explosions of material out of
the vent and the collapse of material
back into vent
Caldera
• Much larger depression that
forms when magma chamber
empties and its roof collapses
Lava Plateau
• Forms when lava erupts from long cracks, or fissures,
and spreads out evenly (thousands of km)
What causes volcanoes?
The Formation of Magma
• Mantle rock melts when the
temperature increases
or the pressure decreases.
What causes volcanoes?
Where Volcanoes Form
• Tectonic Plate Boundaries!!!
~75% world’s active volcanoes in Ring of Fire
What causes volcanoes?
What causes volcanoes?
Hot Spots
How do volcanologists predict
eruptions?
• Measuring Small Quakes
– Before eruption, increase in number & intensity
• Measuring Slope
– Bulges may form with magma (tiltmeter)
• Measuring Volcanic Gases
– Outflow of volcanic gases
• Sulfur dioxide, carbon dioxide
• Measuring Temperature from Orbit
– Measure changes in temperature over time
You should not be a
Volcanologist if….
Robert
McGimsey
USGS
A. Ozerov
• You don’t like
hiking,
backbacking,
rockclimbing, etc.
• You are not
interested in
experiencing
extreme
temperatures
and heights.
• If you don’t like
to travel to
incredible places
and see
breathtaking
views of the
world.
1. Place 10mL of baking soda in center of a sheet of
bathroom tissue. Fold the corners over the baking soda
and crease the edges so that they stay in place. Place
the tissue packet in the middle of a large disposable
pan.
2. Put modeling clay around the top edge of a funnel.
Turn the funnel upside down over the tissue packet.
Press down to make a tight seal.
3. Put safety goggles on and add 50mL of vinegar and
several drops of liquid dish soap to a 200mL beaker,
and stir.
4. Predict how much time will elapse before your volcano
erupts. WRITE THIS DOWN!
5. Pour the liquid into the upturned funnel. Using a
stopwatch, record the time you began to pour and the
time your volcano erupts.
6. How close was your prediction?
4. What did you learn?
Write/draw this in your
science journal.
a. Was your time prediction close to the real
time of eruption?
b. Are the eruption times similar for every
group? If not, give at least one reason why
this might be.
c. How is our experiment different from
predicting the eruption of a real volcano?