Dancing with VolcanoesBethany Ehlmannson

Gillian Galford

The Hawaiian Archipelago

North

Type of Volcanoes

Composite volcanoes have steep slopes

Hawaii’s shield volcanoes slope very gradually

The Big Five

Mauna Loa

HualalaiMauna Kea

Kilauea

Kohala

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

Tephra

Bombs

Spherical

Fusiform

Cow dung

Vesicles in an ash particle

Pele’s tears

Limu o Pele

Pele

Pele’s Hair

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?

Lava flows

Poor air quality

Tourism

But oh no!

Before

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