Dynamic Earth Class 9 7 February 2006. Any Questions?
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Transcript of Dynamic Earth Class 9 7 February 2006. Any Questions?
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