Dynamic EarthDynamic Earth

Class 9Class 9

7 February 20067 February 2006

Any Questions?Any Questions?

Note:Note:Exam #1Exam #1

Date shown on hardcopy Date shown on hardcopy syllabus atsyllabus at

February 14February 14thth, but said February , but said February 1515thth..

The correct date is The correct date is February 14February 14th th

(On-line version is correct)(On-line version is correct)

Elastic Rebound TheoryElastic Rebound Theory

Elastic Rebound TheoryElastic Rebound Theory

Seismograph Record and Seismograph Record and Pathway Pathway

of Three Types of Seismic of Three Types of Seismic Waves Waves

World Seismicity, 1963–2000World Seismicity, 1963–2000

Plate Margin VolcanismPlate Margin Volcanism

Hawaiian VolcanismHawaiian Volcanism

Why do some volcanoes Why do some volcanoes (e.g, Augustine Volcano) (e.g, Augustine Volcano) erupt violently whereas erupt violently whereas other volcanoes (e.g. other volcanoes (e.g. Kilauea Volcano) erupt Kilauea Volcano) erupt relatively quietly?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 HazardVolcanic Hazard

Augustine Earthquake Augustine Earthquake ActivityActivity

Extrusive Intrusive

Basalt Gabbro

Rhyolite GraniteGraniteGranite

Classification of Igneous RocksClassification of Igneous Rocks

Determined by composition (both Determined by composition (both chemical and mineralogical):chemical and mineralogical):magnesium (Mg) + iron (Fe) = magnesium (Mg) + iron (Fe) =

maficmaficfeldspar + quartz (Si) = felsicfeldspar + quartz (Si) = felsic

Classification of Igneous Classification of Igneous rocksrocks

Bowen’s reaction Bowen’s reaction seriesseries Series of chemical reactions that take Series of chemical reactions that take

place in silicate magmas as they coolplace in silicate magmas as they cool

First investigated in the 1920s and First investigated in the 1920s and 1930s by N. L. Bowen1930s by N. L. Bowen

Important experiments that help us Important experiments that help us understand the evolution of magmasunderstand the evolution of magmas

Bowen’s Reaction SeriesBowen’s Reaction Series

Early CrystallizationEarly Crystallization

Fractional crystallizationFractional crystallization

The modification of magma by The modification of magma by crystallization and removal of mineral crystallization and removal of mineral phasesphases

Because only certain elements will go Because only certain elements will go into a given mineral, this will tend to into a given mineral, this will tend to change the composition of the change the composition of the remaining liquidremaining liquid

Magma DifferentiationMagma Differentiation

Magma Chamber Beneath Mid-Magma Chamber Beneath Mid-ocean Spreading Ridgeocean Spreading Ridge

Where do magmas come Where do magmas come from?from?

BasaltsBasalts:: Broadly speaking, we know that Broadly speaking, we know that

mantle rocks (45% SiOmantle rocks (45% SiO22) partially melt (10 to ) partially melt (10 to

15%) to produce basalts (50% SiO15%) to produce basalts (50% SiO22))

Volcanism Due to Partial Volcanism Due to Partial Melting in a Subduction ZoneMelting in a Subduction Zone

Where do magmas come Where do magmas come from?from?

With the addition of some water, basalts will With the addition of some water, basalts will

partially melt to produce partially melt to produce AndesiteAndesite (60% (60%

SiOSiO22))

Factors Affecting Factors Affecting Melting Melting

TemperaturesTemperatures

Tectonic Settings of Igneous Tectonic Settings of Igneous ActivityActivity

Volcanic Island Volcanic Island Arc, IndonesiaArc, Indonesia

Oceanic Oceanic Hot SpotHot Spot HawaiiHawaii

Continental Continental Volcanic ArcVolcanic ArcN. CascadesN. Cascades

Tectonic Settings and Volcanic Tectonic Settings and Volcanic ActivityActivity

Earthquake distribution definesEarthquake distribution definesplate boundariesplate boundaries

December 26, 2004December 26, 2004Earthquake off SumatraEarthquake off Sumatra

Earthquake Focus

Subsidence in Banda AcehSubsidence in Banda Aceh

SubsidenSubsidence in ce in

Banda Banda AcehAceh

TsunamiTsunamiSeries of very

long-wavelength

waves on the ocean

= “tidal wave”

Has nothing to do with tides

/

TsunamiTsunami

Generation of a TsunamiGeneration of a Tsunami

Tsunami waves Tsunami waves

Very small out in the open oceanVery small out in the open ocean Amplitude of only ~ 1 meterAmplitude of only ~ 1 meter Very long wavelengths (up to 100 km)Very long wavelengths (up to 100 km) Travel very fast (as much as 500 mph)Travel very fast (as much as 500 mph)

Tsunami waves Tsunami waves

When waves reach shallow water, they When waves reach shallow water, they "feel" the shallow bottom, just like "feel" the shallow bottom, just like ordinary waves, and they slow down (to ordinary waves, and they slow down (to 20-30 mph)20-30 mph)

Because of the massive energy, this Because of the massive energy, this slowdown causes them to build up very slowdown causes them to build up very high (up to 50-100 m)high (up to 50-100 m)

December 26, 2004December 26, 2004Tsunami in Indian OceanTsunami in Indian Ocean

Hilo: May 23, 1960Hilo: May 23, 1960

Maximum inundation in Hilo (along the Wailoa River) Maximum inundation in Hilo (along the Wailoa River) exceeded half a mile.exceeded half a mile.

Maximum wave height at Hilo was 11 m (36Maximum wave height at Hilo was 11 m (36 ft ft)) 61 people died.61 people died.

Japan: May 24, 1960, 22 hours after Japan: May 24, 1960, 22 hours after the earthquake (7 hours after the Hilo the earthquake (7 hours after the Hilo

tragedy)tragedy)

The tsunami killed 200 people in JapanThe tsunami killed 200 people in Japan

Hilo after 1946 tsunami

1952 Tsunamiwave passingunder bridgeat Haleiwa

Kaiaka Bay

1946 tsunami -- Hilo harbor: 159 fatalities

Beach in Laie, O`ahu before tsunamigenerated by 1957 quake in Aleutians

Runup Runup Maximum height above sea level Maximum height above sea level

reached by a tsunami when it reached by a tsunami when it reaches shorereaches shore

Inundation Inundation Horizontal distance from the normal Horizontal distance from the normal

water's edge reached by a tsunamiwater's edge reached by a tsunami

2000

Tsunami can be generated by Tsunami can be generated by any process that displaces a any process that displaces a

large amount of water: large amount of water: Sub-sea earthquakesSub-sea earthquakes Giant landslides Giant landslides Volcanic eruptionsVolcanic eruptions Meteorite impactsMeteorite impacts

TThurhursdaysday Video: Continental Drift: Legacy of FireVideo: Continental Drift: Legacy of Fire