Transcript Geology of the Hawaiian Islands

Dynamic Earth
Class 9
7 February 2006
Any Questions?
Note:
Exam #1
Date shown on hardcopy syllabus at
February 14th, but said February 15th.
The correct date is February 14th
(On-line version is correct)
Elastic Rebound Theory
Elastic Rebound Theory
Seismograph Record and Pathway
of Three Types of Seismic Waves
World Seismicity, 1963–2000
Plate Margin Volcanism
Hawaiian Volcanism

Why do some volcanoes
(e.g, Augustine Volcano)
erupt violently whereas
other volcanoes (e.g.
Kilauea Volcano) erupt
relatively quietly?
Monday, February 06, 2006 (Associated Press)
S C I E N C E: Augustine Volcano continues to erupt
Augustine Volcano continued to erupt today, with the volcano producing a continuous
crescent-shaped plume of steam, and ash and gas speeding down the flanks of the island
mountain and into the sea.
The Alaska Volcano Observatory made hourly updates on its Web site with each one
beginning the same way — “Eruption is in progress.”
The volcano on an uninhabited island has been erupting since Saturday, with explosions
thrusting particles almost five miles into the skies around south-central Alaska. With winds
shifting the ash away from major air routes, airlines cautiously resumed dozens of flights
that had been canceled as a precaution. Ash particles can damage engines. Alaska Airlines
on Tuesday resumed all flights to and from Kodiak Island and Anchorage, the state’s
largest air hub, said spokeswoman Amanda Tobin. The airline had canceled all of its 36
Anchorage flights Monday night as a precaution. Flights to and from Kodiak had been
canceled Sunday and Monday.
Volcanic Hazard
Augustine Earthquake Activity
Extrusive
Basalt
Rhyolite
Intrusive
Gabbro
Granite
Classification of Igneous Rocks
 Determined
by composition (both
chemical and mineralogical):
 magnesium (Mg) + iron (Fe) =
mafic
 feldspar + quartz (Si) = felsic
Classification of Igneous rocks
Bowen’s reaction series

Series of chemical reactions that take
place in silicate magmas as they cool

First investigated in the 1920s and
1930s by N. L. Bowen

Important experiments that help us
understand the evolution of magmas
Bowen’s Reaction Series
Early Crystallization
Fractional crystallization
The modification of magma by
crystallization and removal of mineral
phases
 Because only certain elements will go
into a given mineral, this will tend to
change the composition of the
remaining liquid

Magma Differentiation
Magma Chamber Beneath Midocean Spreading Ridge
Where do magmas come from?

Basalts: Broadly speaking, we know that
mantle rocks (45% SiO2) partially melt (10 to
15%) to produce basalts (50% SiO2)
Volcanism Due to Partial Melting in
a Subduction Zone
Where do magmas come from?

With the addition of some water, basalts will
partially melt to produce Andesite (60%
SiO2)
Factors Affecting
Melting
Temperatures
Tectonic Settings of Igneous
Activity
Volcanic Island
Arc, Indonesia
Oceanic
Hot Spot
Hawaii
Continental
Volcanic Arc
N. Cascades
Tectonic Settings and Volcanic Activity
Earthquake distribution defines
plate boundaries
December 26, 2004
Earthquake off Sumatra
Earthquake Focus
Subsidence in Banda Aceh
Subsidence
in Banda
Aceh
Tsunami
Series of very
long-wavelength
waves on the
ocean
/ “tidal wave”
=
Has nothing to do
with tides
Tsunami
Generation of a Tsunami
Tsunami waves
Very small out in the open ocean
 Amplitude of only ~ 1 meter
 Very long wavelengths (up to 100 km)
 Travel very fast (as much as 500 mph)

Tsunami waves
When waves reach shallow water, they
"feel" the shallow bottom, just like
ordinary waves, and they slow down (to
20-30 mph)
 Because of the massive energy, this
slowdown causes them to build up very
high (up to 50-100 m)

December 26, 2004
Tsunami in Indian Ocean
Hilo: May 23, 1960



Maximum inundation in Hilo (along the Wailoa
River) exceeded half a mile.
Maximum wave height at Hilo was 11 m (36 ft)
61 people died.
Japan: May 24, 1960, 22 hours after the
earthquake (7 hours after the Hilo tragedy)

The tsunami killed 200 people in Japan
Hilo after 1946 tsunami
Kaiaka Bay
1952 Tsunami
wave passing
under bridge
at Haleiwa
1946 tsunami -- Hilo harbor: 159 fatalities
Beach in Laie, O`ahu before tsunami
generated by 1957 quake in Aleutians
Runup

Maximum height above sea level
reached by a tsunami when it
reaches shore
Inundation

Horizontal distance from the normal
water's edge reached by a tsunami
2000
Tsunami can be generated by any
process that displaces a large
amount of water:
Sub-sea earthquakes
 Giant landslides
 Volcanic eruptions
 Meteorite impacts

Thursday

Video: Continental Drift: Legacy of Fire