Transcript Volcano - Muskegon Area ISD

Volcanoes
7.1 Volcanoes and Plate Tectonics
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Magma – hot liquid rock
Volcanism – movement of magma toward suface
Lava – magma on the surface
Vent – structure which magma flows to surface
Volcano – material built up around the vent
Fissures – cracks, Iceland
Hot spots – volcanism in plate
http://www.nationalgeographic.com/forcesofnature/interactive/index.html?section=v
Where are Volcanoes?
P.11
• Subduction zones
• Mid-ocean ridges
• Hot spots
- found within a plate not at a plate
boundary
Magma
p.12
• Magma is a complex high-temperature
fluid substance. Temperatures of most
magmas are in the range 700°C to 1300°C
• May reach as hot as 1600°C.
• Called magma when in the earth and lava
when it is on the surface of the earth.
Felsic Magma
p.13
– SiO2 >70%
– Fe-Mg: ~ 2%
– Temp: < 900°C
– Viscosity: High
– Eruptive behavior: explosive
– Distribution: hot spots in continental crust
(Yellowstone National Park), continental rifts,
island arcs
Yellowstone
• The Yellowstone Caldera is the largest volcanic
system in North America. It has been termed a
"supervolcano" because the caldera was formed
by exceptionally large explosive eruptions.
• The amount of ash and gases released into the
atmosphere probably caused significant impacts
to world weather patterns and led to the
extinction of many species, primarily in North
America.
Gases from Volcanoes p.14
• Water vapor is typically the most abundant
volcanic gas, followed by carbon dioxide
and sulfur dioxide.
• Sulfur dioxide kills vegetation and can
cause acid rain.
Homework
After viewing the video, write a paragraph
that states what fact you found the most
interesting (disturbing) and why?
Eruptions
7.2 Volcanic Eruptions
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A. Kinds of Eruptions
B. Volcanic Rock Fragments
C. Volcanic Features
1. Types of volcanoes
2. Craters and Calderas
D. Predicting Volcanic Eruptions
Volcanic Eruptions
• 2 types of lava chemically, effects eruptions intensity
• 1. mafic lava – dark, rich in Mg and Fe
• From ocean crust
• Less explosive, quiet
• 2. felsic lava – lighter color, lots of silica, much less Mg and Fe
• Found in continental crust
• More explosive, contains dissolved gases
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Other types are in between
Pahoehoe – mafic lava cooling rapidly will wrinkle
Aa – when the lava breaks into chunks
Pillow lava – midocean ridge cools so rapidly forms round blobs
Pahoehoe
Aa
A. Kinds of Eruptions
• If magma has a lot of gases more
explosive
• Ocean islands usually quiet
• Continental volcanoes with felsic lava
have cooler and thicker lava so traps
gases (H2O and CO2) big explosions
B. Volcanic Rock Fragments
• Felsic lava explodes so throws materials
• Pyroclastic material – rock fragments (some still
molten, others cooled)
• Volcanic ash - <2 mm
• Volcanic dust - <.25 mm
• Lapilli - < .64 mm
• Volcanic bombs – red-hot lava cools in the air in
shape of spiral or round bomb
• Volcanic blocks – big solid rocks as big as a
house
bombs
Volcanoes Can Cause Climate
Change!
• Ash from a large volcano can shut out the
sunlight for hundreds of miles.
C. Volcanic Features
• What it looks like
• 1. Types of volcanoes
• 2. Craters and Calderas
1. Types of volcanoes
• 1. Shield volcanoes – cones with broad base
and gentle slope, made up of lava layers
• Hawaii
• 2. Cinder cones – cone is made up of fragments
ejected
• 3. Composite volcanoes (stratovolcanoes)
• Combination of layers of lava and fragments
from some quiet and expolsive eruptions
• Ex. Mt. Fuji, Rainier, Hood, Shasta
• St. Helens
Types
2. Craters and Calderas
• Crater – funnel-shaped on the top vent
• Explosion forms
• Caldera – depression from collapsed
crater
• Crater Lake National Park
Caldera
Crater Lake - Oregon
D. Predicting Volcanic Eruptions
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Not where we need to be yet
Saves lives
Seismographs
Temp
Pressure
Bulging surface
Gases given off
History/past
Dormant for long periods can be active
7.3 Extraterrestrial volcanism
• Moon
• Mars
• Lo
Moon
Surface covered with craters – meteorites
Lava flow evidence does show volcanic
activity long ago
Nothing active
No plates for movement or convection
current evidence
? Not sure how
Mars
• See pictures of
• None prove active
• They are much larger than earths
because no continental drift
Lo
• Moon of Jupiter
• Pictures of active volcanoe
• Think the material is sulfur and sulfur
dioxide from color
• Constantly erupting