volcanic rock chapter 14 earth science book read pages 252-256 restate & answer topic questions...

Volcanic RockVolcanic RockChapter 14 Earth Science BookChapter 14 Earth Science Book

read pages 252-256read pages 252-256restate & answer Topic Questions 1-6restate & answer Topic Questions 1-6

Essay # 4Essay # 4

MagmaMagmaTopic 1: Page 253 Earth Textbook

Molten Rock UndergroundMolten Rock Underground

Lava: Molten Rock on the SurfaceLava: Molten Rock on the Surface

Volcano: Where Magma erupts as LavaVolcano: Where Magma erupts as Lava

Earth’s layers can be classified based on Earth’s layers can be classified based on composition.composition.

http://www.llnl.gov/str/JulAug04/gifs/Fried1.jpghttp://www.llnl.gov/str/JulAug04/gifs/Fried1.jpg

CrustCrust• 1% of Earth’s volume1% of Earth’s volume• oceanic crustoceanic crust

• mostly mostly basaltbasalt• continental crustcontinental crust

• mostlymostly granite granite

MantleMantle• 83% of Earth’s volume83% of Earth’s volume• mainly mainly siliconsilicon and and oxygenoxygen

CoreCore• 16% of Earth’s volume16% of Earth’s volume• mainly mainly ironiron (90%) and (90%) and nickelnickel

Earth’s layers can also be classified byEarth’s layers can also be classified by physical physical propertiesproperties..

LithosphereLithosphere• cool, rigidcool, rigid

AthenosphereAthenosphere • hot, partially meltedhot, partially melted

Lower mantleLower mantle

CoreCore• outer coreouter core

• liquidliquid• inner coreinner core

• solidsolid• 6,6006,600ooC!C!

MagmaMagmaTopic 1: Page 253 Earth Textbook

FELSICFELSIC: High concentrations of : High concentrations of SILICASILICA. . Light in color, Light in density. Can contain Light in color, Light in density. Can contain trapped gasses. Associated with explosive trapped gasses. Associated with explosive

volcanic eruptions.volcanic eruptions.

MAFICMAFIC: High concentrations of : High concentrations of IronIron & & Magnesium. Magnesium. Dark in color. Heavier in Dark in color. Heavier in

density. Gasses are not usually present. density. Gasses are not usually present. Associated with non-explosive eruptionsAssociated with non-explosive eruptions

Which is which? How do you Which is which? How do you know?know?

Felsic or Mafic?Felsic or Mafic?

Felsic: Light Felsic: Light overall coloroverall color

Mafic: Dark overall Mafic: Dark overall colorcolor

Which is which? How do you Which is which? How do you know?know?

Felsic or Mafic?Felsic or Mafic?

FELSIC & MAFIC ROCKSFELSIC & MAFIC ROCKS

Igneous Rock IdentificationIgneous Rock Identification Felsic Granite, Rhyolite, Obsidian, Felsic Granite, Rhyolite, Obsidian,

PummicePummice High in Si + OHigh in Si + O Low in Fe + MgLow in Fe + Mg Mostly feldspar & quartzMostly feldspar & quartz Light-coloredLight-colored

Mafic (Gabbro, Basalt, Scoria)Mafic (Gabbro, Basalt, Scoria) ““Low” in Si + OLow” in Si + O High in Fe + MgHigh in Fe + Mg no quartz, abundant ferromagnesian mineralsno quartz, abundant ferromagnesian minerals Dark coloredDark colored

Intermediate (Diorite)Intermediate (Diorite)

VolcanoesVolcanoesVolcanoesVolcanoes Volcanoes are the result of hot spots within the Volcanoes are the result of hot spots within the

crust or mantle of the earth.crust or mantle of the earth. The hot, liquid rock will break through weak The hot, liquid rock will break through weak

spots in the surface and form volcanoes or flood spots in the surface and form volcanoes or flood basalts.basalts.

Many volcanoes do not release lava, instead Many volcanoes do not release lava, instead they spit ash and small bits of lava called lapilli.they spit ash and small bits of lava called lapilli.

Some eruptions are quiet with very fluid (low Some eruptions are quiet with very fluid (low viscosity) lava flows while others are explosiveviscosity) lava flows while others are explosive

Volcanism is mostly focused at plate margins

Pacific Ring of FirePacific Ring of Fire

Subduction EruptionsSubduction Eruptions

Topic 6: Page 256 Earth Textbook

*occur at subduction boundaries*erupt violently with gasses

*usually contain felsic magma

TrenchTrench

VolcanoesVolcanoesVolcanoesVolcanoes

Mt. St. Helen before the explosive eruption

VolcanoesVolcanoesVolcanoesVolcanoes

VolcanoesVolcanoesVolcanoesVolcanoes

Mt. St. Helen after the eruption

VolcanoesVolcanoesVolcanoesVolcanoes

VolcanoesVolcanoesVolcanoesVolcanoes

Rift EruptionsRift Eruptions

Topic 5: Page 256 Earth Textbook

*occur at spreading centers*erupt as slow flows with few gasses

*usually contain mafic magma

RidgeRidge

- Subduction - Rifting - Hotspots- Subduction - Rifting - Hotspots

Volcanoes are formed by:Volcanoes are formed by:

VolcanoesVolcanoesVolcanoesVolcanoes

Quiet lava flows

Flood basaltsFlood basaltsFlood basaltsFlood basalts

VolcanoesVolcanoesVolcanoesVolcanoes

Flood basaltsFlood basaltsFlood basaltsFlood basaltsBasalt is a type of rock that is produced from the mantleBasalt is a type of rock that is produced from the mantle

Volcano locationsVolcano locationsVolcano locationsVolcano locations

Hot mantle plumes breaching the Hot mantle plumes breaching the surface in the middle of a tectonic surface in the middle of a tectonic plateplate

What are Hotspot Volcanoes?What are Hotspot Volcanoes?

Photo: Tom Pfeiffer / www.volcanodiscovery.com

The Hawaiian island chain are examples of hotspot volcanoes.

Pacific Ring of FirePacific Ring of Fire

Hotspot volcanoes

The tectonic plate moves over a fixed hotspot forming a chain of volcanoes.

The volcanoes get younger from one end to the other.

Mid-Plate HotspotsMid-Plate HotspotsMid-Plate HotspotsMid-Plate Hotspots

HotspotHotspot

Mid-Plate HotspotsMid-Plate HotspotsMid-Plate HotspotsMid-Plate Hotspots

Mid-Plate HotspotsMid-Plate HotspotsMid-Plate HotspotsMid-Plate Hotspots

VolcanoesVolcanoesVolcanoesVolcanoesShield

EarthquakesEarthquakesChapter 15 Earth Science BookChapter 15 Earth Science Book

read pages 270-273read pages 270-273restate & answer Topic Questions 1-4restate & answer Topic Questions 1-4

Essay # 5Essay # 5

shaking of the Earth’s crust caused by a release shaking of the Earth’s crust caused by a release of energy. Movement of lithospheric platesof energy. Movement of lithospheric plates

What is an Earthquake?What is an Earthquake?Topic 1: Page 271 Earth Textbook

* over a million a year on Earth

* one every 30 seconds

Causes of EarthquakesCauses of Earthquakes

Topic 2: Page 271 Earth Textbook

*eruption on a volcano*collapse of a cavern*impact of a meteor

*Major Cause is the release of stress between two lithospheric plates.

Causes of EarthquakesCauses of Earthquakes

Topic 2: Page 271 Earth Textbook

* Elastic Rebound Theory - Overtime plates move, friction holds plates until they release and suddenly snap back into place

*Major Cause is the release of stress between two lithospheric plates.

Depth of EarthquakesDepth of EarthquakesTopic 3: Page 272 Earth Textbook

* Spreading centers/sliding boundaries tend to be shallow – less than 30 km

depends on the type of plate boundarydepends on the type of plate boundary

* Subduction boundaries however plunge to depths of 700km down

Earthquake TermsEarthquake TermsTopic 3: Page 272 Earth Textbook

* Focus – the point on the fault plane where movement occurs

* Epicenter – the point on the surface directly above the focus

Diagram on page 272

EarthquakesEarthquakesEarthquakesEarthquakes

Earthquake WavesEarthquake WavesTopic 4: Page 273 Earth Textbook

P waves, S waves, L wavesP waves, S waves, L waves

The speed of a wave depends on the material The speed of a wave depends on the material they are passing throughthey are passing through

The more dense the material the faster the wave The more dense the material the faster the wave travels (dominoes closer together – faster)travels (dominoes closer together – faster)

Earthquake WavesEarthquake WavesTopic 4: Page 273 Earth Textbook

P wavesP waves

* primary wave, fastest wave

* material moves back and forth* compressional wave, like sound

* travels through solid liquid & gas

Earthquake WavesEarthquake WavesTopic 4: Page 273 Earth Textbook

S wavesS waves

* secondary wave, slower than P

* material moves side to side* shear wave

* travels through solids only

Earthquake WavesEarthquake WavesTopic 4: Page 273 Earth Textbook

L wavesL waves

* Love wave, slowest wave

* material moves like ripples on pond* surface wave

* travels through solid liquid & gas

Earthquakes generate Earthquakes generate seismic waves.seismic waves.

Seismic waves form in two types:Seismic waves form in two types:

1)1) surface wavessurface waves• sometimes seen as an sometimes seen as an

wavelike motion in the wavelike motion in the groundground

• cause most of the property cause most of the property damage in an earthquake damage in an earthquake

2) 2) body waves (P and S waves)body waves (P and S waves)• useful for analyzing Earth’s useful for analyzing Earth’s

interior structureinterior structurehttp://ja.wikipedia.org/wiki/%E7%94%BB%E5%83%8F:Pswaves.jpghttp://ja.wikipedia.org/wiki/%E7%94%BB%E5%83%8F:Pswaves.jpg

Seismic waves travel through Earth and along its surface.Seismic waves travel through Earth and along its surface.

Body wavesBody waves

1) 1) P (primary) waveP (primary) wave

2) 2) S (secondary) waveS (secondary) wave

• a compressional wavea compressional wave• similar to a sound wavesimilar to a sound wave

• pass through pass through liquids liquids and and solidssolidshttp://www.met.gov.pk/Subpage4/waves_files/pwave_web.jpghttp://www.met.gov.pk/Subpage4/waves_files/pwave_web.jpg

• a shear wavea shear wave• like a rope shaken side to sidelike a rope shaken side to side

• pass through pass through solids onlysolids only• about 1/2 the speed of P wavesabout 1/2 the speed of P waves

http://www.geo.uib.no/jordskjelv/img/s-wave.jpghttp://www.geo.uib.no/jordskjelv/img/s-wave.jpg

seismographseismograph

P waves are faster than S wavesP waves are faster than S waves

About 6 km/sec

About 3.5 km/sec

How do we locate theHow do we locate the epicenter epicenter of an earthquake?of an earthquake?

http://zog.typepad.com/malaysia/epicenter.jpghttp://zog.typepad.com/malaysia/epicenter.jpg

Sumatra-Andaman earthquake (26 December 2004)Sumatra-Andaman earthquake (26 December 2004)

http://www.calstatela.edu/faculty/acolvil/earthquakes.htmlhttp://www.calstatela.edu/faculty/acolvil/earthquakes.html

http://www.theimage.com/geology/notes15/index.htmlhttp://www.theimage.com/geology/notes15/index.html

http://ja.wikibooks.org/wiki/%E9%98%B2%E7%81%BD_%E5%9C%B0%E9%9C%87http://ja.wikibooks.org/wiki/%E9%98%B2%E7%81%BD_%E5%9C%B0%E9%9C%87

If the Earth were If the Earth were homogenous,homogenous, the paths of seismic waves the paths of seismic waves would be straight lineswould be straight lines

http://cires.colorado.edu/~bilham/oldham.gifhttp://cires.colorado.edu/~bilham/oldham.gif

Richard OldhamRichard Oldham• British geologistBritish geologist

If the Earth were If the Earth were homogenous,homogenous, the paths of seismic waves the paths of seismic waves would be straight lineswould be straight lines

http://cires.colorado.edu/~bilham/oldham.gifhttp://cires.colorado.edu/~bilham/oldham.gif

Richard OldhamRichard Oldham• British geologistBritish geologist

Found that seismic waves Found that seismic waves arrived earlier than arrived earlier than expected at seismographs expected at seismographs far from the quakefar from the quake

waves traveled faster as waves traveled faster as they went into Earththey went into Earth

Earthquake wave shadow zones confirmed the presence of Earth’s core.Earthquake wave shadow zones confirmed the presence of Earth’s core.

refractionrefraction

http://www.greatdreams.com/alaska/alaska-collapse-1964.jpghttp://www.greatdreams.com/alaska/alaska-collapse-1964.jpg

Anchorage, AlaskaAnchorage, Alaska27 March 196427 March 19649.2 on Richter scale9.2 on Richter scale

Data from an earthquake confirmed the model of Earth layering.Data from an earthquake confirmed the model of Earth layering.

P and S waves were very large P and S waves were very large and easily detected at great and easily detected at great distancesdistances• helped confirm the models of helped confirm the models of Earth layering. Earth layering.

As with volcanoes, earthquakes are As with volcanoes, earthquakes are not not randomly distributed over the globerandomly distributed over the globe

At the boundaries between plates, friction At the boundaries between plates, friction causes them to stick together. When built up causes them to stick together. When built up energy causes them to break, earthquakes energy causes them to break, earthquakes occur.occur.

Figure showing the distribution of earthquakes around the globe

Where do earthquakes form? Where do earthquakes form?

Figure showing the tectonic setting of earthquakes

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Tidal waves or Tsunamis result when a large section of the sea floor suddenly moves and therefore displaces a massive amount of water.

EarthquakesEarthquakesEarthquakesEarthquakes

Location of worldwide earthquakes

EarthquakesEarthquakesChapter 15 Earth Science BookChapter 15 Earth Science Book

read pages 270-273read pages 270-273restate & answer Topic Questions 1-4restate & answer Topic Questions 1-4

Essay # 5Essay # 5