Volcanoes

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VolcanoesVolcanoes

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Bill Nye Bill Nye VolcanoVolcanoVideoVideo

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What is a Volcano?What is a Volcano?

A volcano is a weak spot in the crust A volcano is a weak spot in the crust where molten material, or magma, where molten material, or magma, comes to the surfacecomes to the surface

Magma reaching the surface is called Magma reaching the surface is called lavalava

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Location of VolcanoesLocation of Volcanoes

600 active volcanoes worldwide600 active volcanoes worldwide

Many more are found beneath Many more are found beneath oceansoceans

Most occur in belts that extend Most occur in belts that extend across continents and oceansacross continents and oceans

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Burning Ring of FireBurning Ring of Fire A major belt is the “Ring of Fire” A major belt is the “Ring of Fire”

which encircles the Pacific Ocean which encircles the Pacific Ocean

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Most volcanoes occur along Most volcanoes occur along diverging plate boundaries diverging plate boundaries

such as the mid-ocean ridge, such as the mid-ocean ridge, or in subduction zones, or in subduction zones,

around edges of oceans around edges of oceans

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““Hot Spot” volcanoes form where magma Hot Spot” volcanoes form where magma from deep within the mantle melts through from deep within the mantle melts through the crust like a blow torchthe crust like a blow torch

– Examples:Examples:

– Hawaiian IslandsHawaiian Islands

– Yellowstone National ParkYellowstone National Park

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HawaiianHawaiian Hot spots Hot spots

Video Video

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Inside a VolcanoInside a Volcano

All volcanoes have a pocket of All volcanoes have a pocket of magma beneath the surface and one magma beneath the surface and one or more cracks through which or more cracks through which magma forces its way throughmagma forces its way through

Magma pocket is called a Magma pocket is called a magma magma chamberchamber

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A A pipepipe is a long tube in the ground is a long tube in the ground that connects the magma chamber that connects the magma chamber to the earth’s surfaceto the earth’s surface

Molten rock and gas leave the Molten rock and gas leave the volcano through an opening called a volcano through an opening called a ventvent

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A A lava flowlava flow is the area covered by is the area covered by lava as it pours out of a ventlava as it pours out of a vent

A A cratercrater is a bowl-shaped area that is a bowl-shaped area that may form at the top of a volcano may form at the top of a volcano around the central vent around the central vent

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Types of Volcanic EruptionsTypes of Volcanic Eruptions

The silica content of magma helps to The silica content of magma helps to determine whether the volcanic determine whether the volcanic eruption is quiet or explosiveeruption is quiet or explosive

Silica is the material formed from the Silica is the material formed from the elements silicon and oxygenelements silicon and oxygen

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Silica is one of the most abundant Silica is one of the most abundant materials in Earth’s crust and mantlematerials in Earth’s crust and mantle

The more silica that magma The more silica that magma contains, the thicker it is contains, the thicker it is

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Quiet Eruptions:Quiet Eruptions:

Magma flows easily; the gas dissolved in Magma flows easily; the gas dissolved in the magma bubbles out gentlythe magma bubbles out gently

Creates island arcs which are a chain of Creates island arcs which are a chain of volcanic islandsvolcanic islands

– Examples:Examples:

– HawaiiHawaii

– IcelandIceland

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Produce two types of lava:Produce two types of lava:

PahoehoePahoehoe - fast moving, hot lava; - fast moving, hot lava; Surface looks like a solid mass of Surface looks like a solid mass of wrinkles, billows, and rope-like coilswrinkles, billows, and rope-like coils

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AaAa - cooler, slower-moving lava; - cooler, slower-moving lava; when hardens, forms a rough surface when hardens, forms a rough surface consisting of jagged lava chunks.consisting of jagged lava chunks.

MaficMafic- rich in magnesium and iron; - rich in magnesium and iron;

this is the kind of lava flows out of this is the kind of lava flows out of oceanic volcanoes.oceanic volcanoes.

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Explosive Eruptions:Explosive Eruptions:

Magma is thick and stickyMagma is thick and sticky

Magma slowly builds up in the Magma slowly builds up in the volcanoes’ pipe volcanoes’ pipe Dissolved gases cannot escapeDissolved gases cannot escape

Trapped gasses build up pressure Trapped gasses build up pressure until they explodeuntil they explode

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A A pyroclastic flowpyroclastic flow occurs when an occurs when an explosive eruption hurls out ash, explosive eruption hurls out ash, cinder, bombs, and gasses cinder, bombs, and gasses

Another name for this kind of lava is Another name for this kind of lava is called called tephra.tephra.

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Stages of a VolcanoStages of a Volcano

ActiveActive - is erupting, or has shown signs - is erupting, or has shown signs that it may erupt in the near futurethat it may erupt in the near future

DormantDormant - does not show signs of - does not show signs of erupting in the neat futureerupting in the neat future

ExtinctExtinct - unlikely to erupt - unlikely to erupt

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Types of VolcanoesTypes of Volcanoes

– Shield VolcanoShield Volcano::

– Thin layers of lava pour out of a vent Thin layers of lava pour out of a vent and harden on top of previous layersand harden on top of previous layers

– Example: Hawaiian IslandsExample: Hawaiian Islands

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Cinder Cone VolcanoCinder Cone Volcano::

– Form when cinders from a vent, pile up Form when cinders from a vent, pile up around the vent, forming a steep- cone-around the vent, forming a steep- cone-shaped mountainshaped mountain

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Composite VolcanoComposite Volcano

Layers of lava alternate with layers Layers of lava alternate with layers of ash, cinders, and bombsof ash, cinders, and bombs

Types of volcano music videoTypes of volcano music video

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1. FYI-Super1. FYI-SuperVolcanoVolcanovideovideo

2. Super volcano simulated 2. Super volcano simulated eruption videoeruption video

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Related Volcanic ActivitiesRelated Volcanic Activities

Hot SpringHot Spring - groundwater heated by a - groundwater heated by a nearby body of magma rises to the surface nearby body of magma rises to the surface and collects in a natural pooland collects in a natural pool

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GeyserGeyser - forms when rising hot - forms when rising hot water and steam become trapped water and steam become trapped underground in a narrow crackunderground in a narrow crack

Pressure builds until the mixture Pressure builds until the mixture suddenly sprays upward, clearing the suddenly sprays upward, clearing the crack crack

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Related Volcanic LandformsRelated Volcanic Landforms

– CalderaCaldera::

– A large hole at the top of a volcano A large hole at the top of a volcano formed when the roof of a volcano’s formed when the roof of a volcano’s magma chamber collapsesmagma chamber collapses

3333Formation of a Caldera Formation of a Caldera

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– DikeDike::

– A slab of volcanic rock formed when A slab of volcanic rock formed when magma forces itself across rock layersmagma forces itself across rock layers

– vertical rock formationvertical rock formation

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SillSill::

A slab of volcanic rock formed when A slab of volcanic rock formed when magma squeezes between layers of magma squeezes between layers of rockrock(horizontal rock formation)(horizontal rock formation)

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sillsill

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BatholithBatholith::

A mass of rock formed when a large body A mass of rock formed when a large body of magma cooled inside the crust of magma cooled inside the crust

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– Dome MountainsDome Mountains::

Rising magma within the crust is Rising magma within the crust is blocked by layers of rockblocked by layers of rock

Magma forces layers of rock to bend Magma forces layers of rock to bend upward into a dome shapeupward into a dome shape

Example: Black HillsExample: Black Hills

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Dome MountainsDome Mountains

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Watching ActivityWatching Activity

Seismometer – is an instrument that Seismometer – is an instrument that detects Earth’s movements. These detects Earth’s movements. These movements tell if the volcano is movements tell if the volcano is about to blow its top.about to blow its top.

Tiltmeter- measures any change in Tiltmeter- measures any change in the slope of an are. This can tell if the slope of an are. This can tell if the land is bulging and ready to the land is bulging and ready to blow.blow.

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VolcanologistsVolcanologistsScientists that study Scientists that study

volcanoesvolcanoes

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Mount VesuviusMount Vesuvius

Erupted in AD79 near the Erupted in AD79 near the city of Pompeii, Italycity of Pompeii, Italy

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Trapped in TimeTrapped in Time

The volcano eruption was deadlyThe volcano eruption was deadly Lava, ash, hot gases poured out of Lava, ash, hot gases poured out of

the volcanothe volcano The ashes covered everythingThe ashes covered everything For hundreds of years the city For hundreds of years the city

remained buried under the ashremained buried under the ash

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Volcanic RockVolcanic Rock

ObsidianObsidian PumicePumice

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Pompeii –Last DayPompeii –Last Day

http://www.smm.org/pompeii/video/?size=medium

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Vocabulary:Vocabulary:

EruptsErupts VolcanoVolcano MagmaMagma LavaLava ventvent Cinder coneCinder cone Shield coneShield cone Composite coneComposite cone VolcanologistsVolcanologists

Island arcIsland arc SeismometerSeismometer TiltmeterTiltmeter Hot spot Hot spot CalderasCalderas Magma chamberMagma chamber PipePipe Lava flowLava flow cratercrater

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Questions :Questions : What are volcanoes?What are volcanoes? How are they formed?How are they formed? What are the types of volcanoes?What are the types of volcanoes? How do volcanoes change the Earth’s How do volcanoes change the Earth’s

surface?surface? Stages of a volcano?Stages of a volcano? What is the ring of fire?What is the ring of fire? What are the differences between quiet What are the differences between quiet

eruptions and explosive eruptions?eruptions and explosive eruptions? What are the volcanic related landforms?What are the volcanic related landforms?