Download Dancing with Volcanoes

Dancing with Volcanoes
Bethany Ehlmannson
Gillian Galford
The Hawaiian Archipelago
North
Type of Volcanoes
Composite volcanoes have
steep slopes
Hawaii’s shield
volcanoes slope very
gradually
Kohala
The Big Five
Mauna Kea
Hualalai
Mauna Loa
Kilauea
Basaltic Composition Range
• Alkali
– high Na2O &
K2O content
• Tholeiitic
– low alkali content
• Varying SiO2
(silica) content
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
Pillow lava
• Submarine basaltic
eruptions
• Repeated oozing
and quenching of
hot basalt
Extinction
• Surface weathering
• Slow submergence
• Coral reefs and atolls
Surface Formations
Pahoehoe vs. A’a
• Pahoehoe can
become a’a due to
cooling, gas loss,
and crystallization
Columnar basalt
• Slow cooling
• Hexagonal columns
based on atomic
arrangement
• Result of thermal or
tectonic stress
The Summit
Common Features:
• a caldera
• spatter cones
• cinder cones
Spatter Cones
Ejecta
Bombs
Spherical
Fusiform
Cow dung
Vesicles in an ash particle
Tephra
Pele
Limu o Pele
Pele’s Hair
Pele’s tears
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
Seismic Chaos
Cracks in the Earth
• Fissures
• Rift Zones
• Faults
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
Joe vs. the Volcano
When humans and volcanoes collide...
Keoua’s ill-fated expedition
against Kamehameha.
What are the Hazards?
Poor air quality
Lava flows
Tourism
Before
But oh no!
After
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