dancing with volcanoes bethany ehlmannson gillian galford
TRANSCRIPT
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Dancing with VolcanoesBethany Ehlmannson
Gillian Galford
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The Hawaiian Archipelago
North
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Type of Volcanoes
Composite volcanoes have steep slopes
Hawaii’s shield volcanoes slope very gradually
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The Big Five
Mauna Loa
HualalaiMauna Kea
Kilauea
Kohala
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Basaltic Composition Range
• Alkali– high Na2O & K2O
content
• Tholeiitic
– low alkali content
• Varying SiO2 (silica)
content
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Life of a volcano(4 stages of evolution and growth)
• Preshield– Loihi
• Shield-forming – Mauna Loa, Kilauea
• Post-shield – Mauna Kea, Hualalai, Kohala
• Rejuvenation – Kauai
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Pillow lava
• Submarine basaltic
eruptions
• Repeated oozing
and quenching of
hot basalt
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Extinction
• Surface weathering
• Slow submergence
• Coral reefs and atolls
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Surface Formations
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Pahoehoe vs. A’a• Pahoehoe can
become a’a due to
cooling, gas loss, and
crystallization
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Columnar basalt
• Slow cooling
• Hexagonal columns based on atomic arrangement
• Result of thermal or tectonic stress
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The Summit
Common Features:• a caldera• spatter cones• cinder cones
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Spatter Cones
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Ejecta
Tephra
Bombs
Spherical
Fusiform
Cow dung
Vesicles in an ash particle
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Pele’s tears
Limu o Pele
Pele
Pele’s Hair
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Rocks!
• Most abundant single mineral is feldspar, esp. plagioclase
• Olivine and augite are common dark minerals– tiny grains of magnetite can separate in
low grade metamorphism
• Xenoliths of periodite
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Seismic Chaos
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Cracks in the Earth
• Fissures
• Rift Zones
• Faults
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Earthquakes• Thousands of earthquakes
per year• Most can’t be felt, a few
cause mild damage• Causes:
>Magma movement
-causes little damage
except near the site
-may be indicators of
eruptions
>Structural weakness
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Joe vs. the Volcano
When humans and volcanoes collide...
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Keoua’s ill-fated expedition against Kamehameha.
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What are the Hazards?
Lava flows
Poor air quality
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Tourism
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But oh no!
Before
After
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Safety Precautions for Working Around Volcanoes
PLEASE READ CAREFULLY-YOUR LIFE MAY DEPEND ON IT
Viewing Lava Safely - Common Sense is Not Enough
What are the Volcanic Hazards Facing you?
•Bench collapse can kill
•Tephra jets & littoral fountains hurl hot lava
•Steam blasts toss rocks
•Vog - Acid fumes and glass particles can irritate eyes and lungs
•Scalding waves burn
•In the event of a strong earthquake which may
cause tsunami, run for high ground immediately
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