Download What are Volcanoes?

Plutonic and
Volcanic Activity
Intrusive Igneous Bodies
What are Plutons?
Concordant plutons 
Laccoliths are _______________________.
Discordant plutons 
Batholiths 
Stocks 
Volcanic pipes 
What is Volcanism?
What are characteristics of the 3 Categories of Volcanoes?
Active volcanoes 
Dormant volcanoes 
Extinct volcanoes 
Kilauea, Hawaii
What are Volcanoes?
What is a Crater?
What is a Caldera?
Crater Lake, Oregon
What is Viscosity?
What influences viscosity?
Magma
Type
Silica
Content
Mafic
45 - 52%
Intermed.
53 - 65
Felsic
> 65
Na, K Al
Ca, Fe, Mg
Increase
Viscosity
low
medium
Increase
high
Composite Volcanoes (Stratovolcanoes)
Mt. St. Helens, WA
Characteristics of Lava Domes
(Mt. Lassen, CA = world’s largest)
Characteristics of Shield volcanoes
Characteristics of Cinder Cones
SP Crater, Arizona
What is
Pahoehoe?
What is
A'a?
What are
Lava Tubes &
how do they form?
What is Pillow lava &
how does it form?
Lava solidifies, contracts, & fractures.
What is Columnar jointing?
Oregon
What are Pyroclastic sheets?
Marella River valley, Philippines
Characteristics of Pyroclastic material
Ash =
Lapilli =
Bombs =
lapilli
bomb
ash
Mt. Lassen, Calif.
Volcanic Gases
________ of gas emitted is
water vapor.
Lesser amounts of CO2, N,
SO2, & H2SO4 are released.
Most gases quickly dissipate.
What 4 things must you have to predict eruptions?
What are Volcanic tremors?
What do they indicate?
1. Swelling (magma moves into reservoir)
2. Shape change (increases in slope & distance b/w surface points)
3. Volcanic tremors are produced.
4. Eruption occurs.
5. Volcano deflates & regains its original shape.
Where are volcanoes found?
Divergent Margins
Mafic magma forms oceanic crust
Quiescent eruptions
Shield volcanoes form along
Mid-Ocean Ridges.
Convergent Margins
Intermed. to Felsic magma
Explosive eruptions
Composite volcanoes & lava
domes comprise volcanic arcs
What is Intraplate Volcanism?
What type of magma is associated with this type of
volcanism?
Where are two
locations of intraplate
volcanism?