Lesson 1 Lesson 1 Mountain Mountain Ranges Ranges and and SystemsSystems

Earth’s two major mountain belts are the circum-Pacific Earth’s two major mountain belts are the circum-Pacific belt and the Eurasian-Melanesian belt.belt and the Eurasian-Melanesian belt.

Where are Where are the the Mountain Mountain BeltsBelts

The circum-Pacific belt forms a ring around the Pacific The circum-Pacific belt forms a ring around the Pacific Ocean (a.k.a. – Ring of Fire) and includes:Ocean (a.k.a. – Ring of Fire) and includes:

The Cascades (North Pacific)The Cascades (North Pacific) The Andes (South America)The Andes (South America)

Where are Where are the the Mountain Mountain BeltsBelts

The Eurasian-Melanesian belt runs from the Pacific islands The Eurasian-Melanesian belt runs from the Pacific islands through Asia and southern Europe and into northwestern through Asia and southern Europe and into northwestern Africa and includes:Africa and includes:

The Alps of EuropeThe Alps of Europe The Himalaya's of AsiaThe Himalaya's of Asia

Mt Baldy 10,000. Mt. Whitney 15,000, Mt. Everest 26,000Mt Baldy 10,000. Mt. Whitney 15,000, Mt. Everest 26,000

Plate Tectonics Plate Tectonics

and Mountainsand Mountains

Mountains form as a result Mountains form as a result of collisions between of collisions between tectonic plates at tectonic plates at convergent boundaries.convergent boundaries.

There are 3 types of There are 3 types of boundaries in which these boundaries in which these collisions happen and collisions happen and unique characteristics that unique characteristics that go with each:go with each:

Check for UnderstandingCheck for Understanding

What are the two major mountain belts What are the two major mountain belts and what mountains ranges are and what mountains ranges are associated with each?associated with each?

How are mountains formed? How are mountains formed? Use your academic Use your academic language. language.

Write using complete sentences and proper grammarWrite using complete sentences and proper grammar. .

Plate Plate Tectonics Tectonics and and MountaiMountai

nsns

(1) Collisions between continents and oceanic crust(1) Collisions between continents and oceanic crust

Plate Plate Tectonics Tectonics and and MountainMountain

ss

(2) Collisions between oceanic crust(2) Collisions between oceanic crust

Plate Plate Tectonics Tectonics and and MountaiMountai

nsns

(3) Collisions between continents(3) Collisions between continents

1) Collisions between 1) Collisions between Continental & Continental & Oceanic CrustOceanic Crust

When oceanic When oceanic lithosphere and lithosphere and continental lithosphere continental lithosphere collide at convergent collide at convergent plate boundaries the plate boundaries the denser oceanic denser oceanic lithosphere subducts lithosphere subducts beneath the continental beneath the continental lithosphere.lithosphere.

This produces large-This produces large-scale deformation scale deformation which uplifts high which uplifts high mountains.mountains.

1) Collisions between 1) Collisions between Continental & Oceanic Continental & Oceanic CrustCrust

Also, the subduction of the Also, the subduction of the oceanic lithosphere causes oceanic lithosphere causes partial melting of the partial melting of the overlying mantle and crust.overlying mantle and crust.

1) Collisions between 1) Collisions between Continental & Oceanic Continental & Oceanic CrustCrust

This melting produces This melting produces volcanic mountains.volcanic mountains.

Examples include the Examples include the Cascades and Andes.Cascades and Andes.

2.) Collisions 2.) Collisions Between Oceanic Between Oceanic Crust & Oceanic Crust & Oceanic CrustCrust

Volcanic mountains Volcanic mountains commonly form where commonly form where two plates whose edges two plates whose edges consist of oceanic consist of oceanic lithosphere collide.lithosphere collide.

2.) Collisions Between 2.) Collisions Between Oceanic Crust & Oceanic Oceanic Crust & Oceanic CrustCrust

In this collision, the In this collision, the denser, colder oceanic denser, colder oceanic plate subducts beneath plate subducts beneath the other oceanic plate.the other oceanic plate...

2.) Collisions 2.) Collisions Between Oceanic Between Oceanic Crust & Oceanic Crust & Oceanic CrustCrust

Subduction again leads Subduction again leads to volcanism and these to volcanism and these eruptions of magma eruptions of magma form an arc of volcanic form an arc of volcanic mountains.mountains.

Examples include the Examples include the Philippine Islands Philippine Islands Japan, New Zealand Japan, New Zealand and Indonesia.and Indonesia.

3.) Collisions 3.) Collisions Between Between ContinentsContinents

Mountains can also form Mountains can also form when two continents when two continents collide.collide.

When the continental When the continental lithosphere of both plates lithosphere of both plates collide, subduction is collide, subduction is stopped because both stopped because both plates have the same plates have the same densities, the collision densities, the collision continues in a upward continues in a upward motion.motion.

3.) Collisions 3.) Collisions Between Between ContinentsContinents

An example of this type An example of this type of collision is the of collision is the formation of the Alps in formation of the Alps in Europe and the Europe and the Himalaya Mountains in Himalaya Mountains in Asia.Asia.

Collisions Collisions Between Between ContinentsContinents

The intense deformation that resulted from the collision uplifted The intense deformation that resulted from the collision uplifted the Himalaya’s, which are growing taller.the Himalaya’s, which are growing taller.

Check for Check for UnderstandingUnderstanding

Draw the following:

Draw the interaction between the Juan De Fuca Plate and the North American Plate. What type of plate collision is this interaction?

Draw the Indian Plate and the Asian Plate collision. What type of collision is this interaction?

Be sure to be clear and concise when identifying your plates. Label all pictures.

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Lesson 2 – Lesson 2 – Types of Types of MountainsMountainsrockies 5:00

Scientists classify mountains according to the way in Scientists classify mountains according to the way in which the crust was deformed.which the crust was deformed.

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Four Types Four Types of of MountainsMountains

(1) Folded Mountains(1) Folded Mountains

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Types of Types of MountainsMountains

(2) Fault-Block Mountains(2) Fault-Block Mountains

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Types of Types of MountainMountainss

(3) Dome Mountains(3) Dome Mountains

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Types of Types of MountainMountainss

(4) Volcanic Mountains(4) Volcanic Mountains

NYIRAGONGO LAVA LAKE

1. Folded 1. Folded MountainsMountains

A folded mountain is a A folded mountain is a mountain that forms when mountain that forms when rock layers are squeezed rock layers are squeezed together and uplifted.together and uplifted.

The highest mountain The highest mountain ranges in the world ranges in the world consist of folded consist of folded mountains that form when mountains that form when continents collide.continents collide.

Boundary type: Boundary type: ConvergentConvergent

1. Folded 1. Folded MountainsMountains

The same stresses that The same stresses that form folded mountains form folded mountains also uplift plateaus.also uplift plateaus.

Arizona

PlateausPlateaus

Plateaus are large, Plateaus are large, flat areas of rock, flat areas of rock, high above sea level high above sea level and located near and located near mountain ranges.mountain ranges.

Plateaus can form Plateaus can form where large areas of where large areas of rock are eroded or rock are eroded or when a large portion when a large portion of flat earth is pushed of flat earth is pushed up from the earth.up from the earth.

Types of Plateau Types of Plateau - Butte- Butte

A butte (French) is an A butte (French) is an isolated hill with steep, isolated hill with steep, often vertical sides and a often vertical sides and a small, relatively flat top; it small, relatively flat top; it is smaller than mesas, is smaller than mesas, and plateaus.and plateaus.

Merrick Butte, Arizona

Types of Plateau-Types of Plateau-MesaMesa

A mesa A mesa (Spanish – (Spanish – table) a flat-table) a flat-topped topped mountain or mountain or hill.hill.

Black Mesa, Arizona

2. Fault-Block 2. Fault-Block MountainsMountains

Fault-block mountains Fault-block mountains form when enormous form when enormous underground underground pressure forces a pressure forces a whole rock mass to whole rock mass to break away from break away from another.another.

Boundary Type: Boundary Type: Transform or Transform or DivergentDivergent

Fault-Block Fault-Block MountainsMountains

On one side of this On one side of this break the rocks rise; break the rocks rise; on the other side on the other side they sink down. they sink down.

2. Fault-Block 2. Fault-Block MountainsMountains

Some of the most Some of the most spectacular spectacular mountain scenery mountain scenery anywhere are the anywhere are the great rock walls of great rock walls of the Sierra Nevada the Sierra Nevada which are actually which are actually the sides of huge the sides of huge tilted fault blocks. tilted fault blocks.

2. Fault-Block 2. Fault-Block MountainsMountains

The Sierra Nevada’s The Sierra Nevada’s are in fact the are in fact the broken upper edge broken upper edge of a huge plate that of a huge plate that tilts down toward the tilts down toward the west.west.

GrabensGrabens

The same type The same type of faulting that of faulting that forms fault-forms fault-block mountains block mountains also forms long, also forms long, narrow valleys narrow valleys called grabens.called grabens.

GrabensGrabens

Grabens Grabens develop when develop when steep faults steep faults break the crust break the crust into blocks and into blocks and one block slips one block slips downward downward relative to the relative to the surrounding surrounding blocks.blocks.

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3. Dome 3. Dome MountainsMountains

Dome mountains are Dome mountains are created when a large created when a large amount of magma amount of magma pushes up from below the pushes up from below the Earth’s crust, but it never Earth’s crust, but it never actually reaches the actually reaches the surface and erupts. surface and erupts.

The pushed up rock (now The pushed up rock (now metamorphic) cools and metamorphic) cools and hardens into hardens into a dome shape.a dome shape.

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3. Dome 3. Dome MountainsMountains

Since the dome is higher Since the dome is higher than its surroundings, than its surroundings, erosion works from the erosion works from the top creating a circular top creating a circular mountain range.mountain range.

Example of this is the Example of this is the Adirondack Mountains in Adirondack Mountains in N.Y.N.Y.

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3. Dome 3. Dome MountainMountainss

Another example is Half-Dome in Yosemite.Another example is Half-Dome in Yosemite.

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4. Volcanic Mountains4. Volcanic Mountains

Volcanic mountains Volcanic mountains are created when are created when magma from magma from beneath the Earth beneath the Earth makes its way to makes its way to the surface. the surface.

When it does get to When it does get to the surface, the the surface, the magma erupts as magma erupts as lava, ash, rock and lava, ash, rock and volcanic gases. volcanic gases.

Krakatoa, Indonesia

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4. Volcanic Mountains4. Volcanic Mountains

This material This material builds up builds up around the around the volcanic vent, volcanic vent, building up a building up a mountain over mountain over time.time.

Calderas - Calderas - demo

The word comes The word comes from Spanish from Spanish calderacaldera, meaning "cooking , meaning "cooking pot."pot."

A Caldera is large, A Caldera is large, circular depression circular depression that forms when the that forms when the magma chamber magma chamber below a volcano below a volcano partially empties and partially empties and causes the ground causes the ground above to sinkabove to sink

CalderasCalderas

Eruptions that Eruptions that discharge large discharge large amounts of amounts of magma can magma can also cause a also cause a caldera to form.caldera to form.

Calderas may Calderas may later fill with later fill with water to form water to form lakes.lakes.

•Crater Lake, Oregon Formed around 7,700 years ago by the collapse of the volcano Mount Mazama

Lahars Lahars (Mudflows)(Mudflows)

““Lahar" is Lahar" is an Indonesian word an Indonesian word that describes that describes volcanic mudflows or volcanic mudflows or debris flows.debris flows.

Lahars have the Lahars have the consistency, viscosity consistency, viscosity and approximately the and approximately the same density same density of concrete: fluid when of concrete: fluid when moving, then solid moving, then solid when stopped.when stopped.

Location of Volcanic Location of Volcanic MountainsMountains

Volcanoes can be found at these types of Volcanoes can be found at these types of boundaries:boundaries:

(1) Convergent subduction plate (1) Convergent subduction plate boundaries (Cascades)boundaries (Cascades)

(2) Divergent plate boundaries (Mid-(2) Divergent plate boundaries (Mid-Atlantic Ridge)Atlantic Ridge)

(3) Hot spots (Hawaii) (3) Hot spots (Hawaii)

HighlightHighlightss

Chapter 13

Lesson 3 Lesson 3 (Ch13) – (Ch13) – VolcanoesVolcanoesScientist on rim of Nyragongo 4:004:00

The cause of many The cause of many volcanic eruptions is due volcanic eruptions is due to the movement of to the movement of tectonic plates which is tectonic plates which is driven by Earth’s internal driven by Earth’s internal heat.heat.

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Why does Rock Stay Why does Rock Stay SolidSolid

Pressure and Pressure and temperature increase as temperature increase as the depth below the the depth below the earth's surface increases earth's surface increases (heat from the core, (heat from the core, pressure from overlying pressure from overlying rocks, etc.). rocks, etc.).

But, because pressure But, because pressure increases along with increases along with temperature, the rocks in temperature, the rocks in the mantle remain solid. the mantle remain solid.

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Why does Rock Stay Why does Rock Stay SolidSolid

For example, a rock's For example, a rock's melting temperature on melting temperature on the surface might be the surface might be 1000 ºC, but 200 km 1000 ºC, but 200 km below the surface under below the surface under much higher pressure, much higher pressure, the melting temperature the melting temperature of the rock might be of the rock might be 1300 ºC.1300 ºC.

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1) Change 1) Change in Pressurein Pressure

So if overlying So if overlying pressure changes pressure changes then so does the then so does the melting point of the melting point of the rock.rock.

Take the example of Take the example of high altitude high altitude cooking.cooking.

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1) Change in Pressure1) Change in Pressure

Boiling TeaBoiling Tea

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2) Addition of 2) Addition of FluidsFluids

The addition of water The addition of water and volatile and volatile contents promote contents promote melting by lowering the melting by lowering the melting temperature of melting temperature of rocks. rocks.

Thus, a dry rock would Thus, a dry rock would have a higher melting have a higher melting point than a rock with point than a rock with water present. water present.

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3) Increased 3) Increased TemperatureTemperature

Lastly increasing the Lastly increasing the temperature of a rock will temperature of a rock will also cause melting.also cause melting.

Difference between Lava and Difference between Lava and MagmaMagma

Magma is liquid rock Magma is liquid rock produced under earth’s produced under earth’s surface.surface.

Because magma is lighter Because magma is lighter then solid rock it flows then solid rock it flows upward away from denser upward away from denser rock and when it reaches rock and when it reaches the surface it is referred the surface it is referred to as lava.to as lava.

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ViscosityViscosity

How explosive a volcano How explosive a volcano is depends on how runny is depends on how runny or sticky the magma is. or sticky the magma is.

The The viscosityviscosity, or , or resistance to flow, of resistance to flow, of magma affects the force magma affects the force with which a particular with which a particular volcano will erupt.volcano will erupt.

Types of MagmaTypes of Magma

Because oxygen and Because oxygen and silicon are by far the silicon are by far the two most abundant two most abundant elements in magma, it elements in magma, it is convenient to is convenient to describe the different describe the different magma types in terms magma types in terms of their silica content of their silica content (SiO2). (SiO2).

Chapter 13

Eruptions and the Eruptions and the ColdCold

You can think of volcanoes in You can think of volcanoes in terms of when we get sick.terms of when we get sick.

Typically with a cold your Typically with a cold your nose is runny (mafic).nose is runny (mafic).

However when you have the However when you have the flu your mucus is thicker flu your mucus is thicker (felsic).(felsic).

Gas Factor in Gas Factor in MagmaMagma

The amount of dissolved The amount of dissolved gas in the magma gas in the magma provides the driving force provides the driving force for explosive eruptions. for explosive eruptions.

The viscosity of the The viscosity of the magma, however, is the magma, however, is the most important factor in most important factor in determining whether an determining whether an eruption will be explosive eruption will be explosive or non-explosive.or non-explosive.

Mafic MagmaMafic Magma

Mafic magmas, have Mafic magmas, have relatively low silica and relatively low silica and high iron (Fe) and high iron (Fe) and magnesium (Mg) magnesium (Mg) contents.contents.

Mafic volcanoes create a Mafic volcanoes create a magma that is “Runny magma that is “Runny like honey”.like honey”.

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Quiet Quiet EruptionsEruptions

Oceanic volcanoes Oceanic volcanoes commonly form from commonly form from mafic based magma.mafic based magma.

Because of mafic Because of mafic magma’s low viscosity magma’s low viscosity (thin and runny), magma (thin and runny), magma is hot (above 1700°F) and is hot (above 1700°F) and gases can easily escape gases can easily escape from mafic magma. from mafic magma.

Chapter 13

Quiet Quiet EruptionsEruptions

Eruptions from oceanic Eruptions from oceanic volcanoes, such as those volcanoes, such as those in Hawaii, are referred to in Hawaii, are referred to as quietas quiet..

Felsic MagmaFelsic Magma

Felsic magmas, have Felsic magmas, have relatively high silica and relatively high silica and low iron (Fe) and low iron (Fe) and magnesium (Mg) magnesium (Mg) contents.contents.

Felsic volcanoes create Felsic volcanoes create magma that is “Thicky like magma that is “Thicky like

Skippy”.Skippy”.

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Explosive Explosive EruptionsEruptions

Unlike the fluid lavas Unlike the fluid lavas produced by oceanic produced by oceanic volcanoes, the felsic lavas of volcanoes, the felsic lavas of continental volcanoes, such continental volcanoes, such as Mount St. Helens, tend to as Mount St. Helens, tend to be cooler (1400°F), thicker be cooler (1400°F), thicker and stickier.and stickier.

If magma is thick and sticky If magma is thick and sticky (high viscosity), then gases (high viscosity), then gases cannot escape as easily.cannot escape as easily.

Chapter 13

Explosive EruptionsExplosive Eruptions

With felsic based lava With felsic based lava pressure builds up until pressure builds up until the gases escape the gases escape violently and explode violently and explode throwing pyroclastic throwing pyroclastic material into the air.material into the air.

Felsic volcanoes are the Felsic volcanoes are the most dangerous and most dangerous and deadly.deadly.

White Island, NZ

Predicting Volcanic Predicting Volcanic EruptionsEruptionsWarning sign #1 - Warning sign #1 - EarthquakesEarthquakes

One of the most One of the most important warning signals important warning signals of volcanic eruptions is an of volcanic eruptions is an increase in earthquake increase in earthquake activity around the activity around the volcano.volcano.

Mt. St. Helens

Predicting Volcanic Predicting Volcanic EruptionsEruptions#2 Change in Mtn. #2 Change in Mtn. GeologyGeology

Also the geology Also the geology may change due to may change due to swelling, subsidence swelling, subsidence and increased gas and increased gas emissions.emissions.

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Predicting Volcanic Predicting Volcanic EruptionsEruptions#3 Using past #3 Using past eruptionseruptions

Predicting the eruption of Predicting the eruption of a particular volcano also a particular volcano also requires some knowledge requires some knowledge of its previous eruptions.of its previous eruptions.

Just like the gap theory Just like the gap theory with earthquakes.with earthquakes.

Mudflows (Lahars) went 17 miles into Mudflows (Lahars) went 17 miles into Columbia riverColumbia river

Elevation was 9,700 ft now it is Elevation was 9,700 ft now it is 8,400 ft8,400 ft

Chapter 13

Next United States Next United States Volcano isVolcano is

Mount RainierMount Rainier, , (14,410 Feet) the (14,410 Feet) the highest volcano in highest volcano in the Cascade the Cascade Range and is Range and is potentially the most potentially the most dangerous volcano.dangerous volcano.

Just outside Seattle Just outside Seattle WashingtonWashington

Chapter 13

Mt. Rainier is Mt. Rainier is considered the next considered the next threat in the U.S.threat in the U.S.

Mount Rainier is Mount Rainier is known to have known to have erupted as recently erupted as recently as in the 1840s, as in the 1840s, and large eruptions and large eruptions took place as took place as recently as about recently as about 1,000 and 2,300 1,000 and 2,300

years ago.years ago.

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Nyiragongo Nyiragongo

scientist

Chapter 13

Lesson 4 - Major Lesson 4 - Major Volcanic ZonesVolcanic Zones

Like earthquakes, most Like earthquakes, most active volcanoes occur in active volcanoes occur in these 3 major zones: these 3 major zones:

1) Subduction Zones 1) Subduction Zones (convergent boundary) (convergent boundary)

2) Mid-Ocean Ridges 2) Mid-Ocean Ridges (divergent boundary)(divergent boundary)

3) Hot Spots3) Hot Spots

The Ring of FireThe Ring of Fire

The Ring of Fire is the The Ring of Fire is the largest subduction zone on largest subduction zone on Earth and is an area where Earth and is an area where large numbers of large numbers of earthquakes and volcanic earthquakes and volcanic eruptions occur. eruptions occur.

The Ring of Fire has 452 The Ring of Fire has 452 volcanoes and is home to volcanoes and is home to over 75% of the world's over 75% of the world's active and dormant active and dormant volcanoes.volcanoes.

Subduction Subduction ZonesZones

At the Ring of Fire you At the Ring of Fire you will find collisions will find collisions between oceanic and between oceanic and continental plates and continental plates and collisions between collisions between oceanic and oceanic oceanic and oceanic plates.plates.

Why do Why do Volcanoes occur Volcanoes occur at Subduction at Subduction ZonesZones

Volcanoes occur at a Volcanoes occur at a subduction zone because subduction zone because the subducting the subducting lithosphere brings down lithosphere brings down moisture and rock.moisture and rock.

The moisture lowers the The moisture lowers the melting point of the melting point of the surrounding rock in the surrounding rock in the area which allows it to area which allows it to melt.melt.

Why do Volcanoes Why do Volcanoes occur at Subduction occur at Subduction ZonesZones

Because liquid Because liquid rock (magma) is rock (magma) is less dense then less dense then the solid rock the solid rock around it, it rises around it, it rises to the surface of to the surface of Earth.Earth.

2) Why do Volcanoes 2) Why do Volcanoes Occur Along Mid-Occur Along Mid-Ocean Ridges & Ocean Ridges & Divergent BoundariesDivergent Boundaries

Hot mantle rock Hot mantle rock rises where the rises where the plates are moving plates are moving apart. apart.

This releases This releases pressure on the pressure on the mantle, which mantle, which lowers its melting lowers its melting temperature. temperature.

2) Mid-Ocean Ridges 2) Mid-Ocean Ridges & Divergent & Divergent BoundariesBoundaries

Lava erupts through Lava erupts through long cracks in the long cracks in the ground, or fissures.ground, or fissures.

Most divergent Most divergent volcanoes happen volcanoes happen underwater and out underwater and out of harms way of of harms way of humans.humans.

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Divergent Divergent Boundaries on Land - Boundaries on Land -

Iceland and AfricaIceland and Africa

There are two There are two exceptions and they exceptions and they are Iceland and Africa. are Iceland and Africa.

Iceland is unique Iceland is unique because ½ of Iceland is because ½ of Iceland is on the North American on the North American plate the other ½ is on plate the other ½ is on the Eurasian plate the Eurasian plate allowing us to see how allowing us to see how volcanoes work at volcanoes work at divergent boundaries.divergent boundaries.

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Divergent Divergent Boundaries on Land Boundaries on Land - Iceland and Africa- Iceland and Africa

Iceland is one of the most Iceland is one of the most active volcanic regions in active volcanic regions in the world, with eruptions the world, with eruptions occurring on average occurring on average roughly every three years roughly every three years (in the 20th century there (in the 20th century there were 39 volcanic were 39 volcanic eruptions on and around eruptions on and around Iceland). Iceland).

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Divergent Divergent Boundaries on Land - Boundaries on Land - Iceland and AfricaIceland and Africa

Africa is another place Africa is another place where we get to witness where we get to witness volcanoes at a divergent volcanoes at a divergent boundary. boundary.

There are 18 active There are 18 active volcanoes along with two volcanoes along with two unusual lava lakes.unusual lava lakes.

Chapter 13

Iceland and Iceland and AfricaAfrica

Example include Example include volcanoes like:volcanoes like:

Erta AleErta Ale

NyiragongoNyiragongo

3) Hot Spots3) Hot Spots

A Hot spot isA Hot spot is a a volcanically active volcanically active area of Earth’s area of Earth’s surface, commonly surface, commonly far from a tectonic far from a tectonic plate boundary.plate boundary.

This occurs because This occurs because hot material called hot material called mantle plumesmantle plumes, rise , rise and reach the and reach the lithosphere.lithosphere.

3) Hot Spots3) Hot Spots

As magma rises to As magma rises to the surface, it the surface, it breaks through the breaks through the overlying crust overlying crust

creating a volcano.creating a volcano.

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Mantle PlumesMantle Plumes

Evidence suggests that Evidence suggests that mantle plumes stay mantle plumes stay stationary while the stationary while the lithospheric plate above a lithospheric plate above a mantle plume continues mantle plume continues to drift slowly.to drift slowly.

So, the volcano on the So, the volcano on the surface is eventually surface is eventually carried away from the carried away from the mantle plume.mantle plume.

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Mantle PlumesMantle Plumes The activity of the volcano The activity of the volcano stops because a hot spot stops because a hot spot that contains magma no that contains magma no longer feeds the volcano.longer feeds the volcano.

However, a new volcano However, a new volcano forms where the lithosphere forms where the lithosphere has moved over the mantle has moved over the mantle plume.plume.

Hot Spot Area’s Hot Spot Area’s Found on EarthFound on Earth

Geologists have Geologists have identified some 40–50 identified some 40–50 such hotspots around such hotspots around the globe, with Hawaii, the globe, with Hawaii, Yellowstone, and the Yellowstone, and the Galápagos, overlying Galápagos, overlying the most currently the most currently active.active.

YellowstoYellowstonene

YellowstoneYellowstone

YellowstoneYellowstone

Why Hot Spots Why Hot Spots OccurOccur

Why these hot spots Why these hot spots (plumes) occur is still (plumes) occur is still disputed to this day by disputed to this day by scientist. scientist.

There are other theories There are other theories out there including: out there including:

1) Crack in the Crust1) Crack in the Crust 2) Reheated slabs2) Reheated slabs 3) Meteorite damage3) Meteorite damage

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1st Theory – 1st Theory – Cracks in the Crust Cracks in the Crust (Earth’s Crust (Earth’s Crust Displacement – ECD)Displacement – ECD)

In theory - Hot-spot In theory - Hot-spot volcanoes occur in long volcanoes occur in long chains because they form chains because they form along cracks in the along cracks in the Earth’s crust.Earth’s crust.

These cracks come from These cracks come from weakness in the weakness in the lithosphere caused by lithosphere caused by former ice sheets melting former ice sheets melting and their displacement of and their displacement of weight.weight.

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22ndnd Theory – Theory – Reheated SlabsReheated Slabs

The reheated slab theory The reheated slab theory states that extra rock, through states that extra rock, through subduction is reintroduced subduction is reintroduced into the mantle creating a into the mantle creating a plume of magma.plume of magma.

3rd Theory – 3rd Theory – Meteorite impactMeteorite impact

The meteor impact theory The meteor impact theory believes that foreign believes that foreign objects crashed into the objects crashed into the Earth’s lithosphere Earth’s lithosphere damaging (puncturing) damaging (puncturing) the rock and allowing the rock and allowing magma to rise through to magma to rise through to the surface.the surface.

Check for Check for UnderstandinUnderstandingg1.1. Draw and describe Draw and describe

how the Hawaiian how the Hawaiian Islands Formed.Islands Formed.

2. Identify the 3 ways 2. Identify the 3 ways in which magma in which magma can reach the can reach the Earth’s surface. Earth’s surface. Provide evidence Provide evidence in which theory in which theory you believe to be you believe to be most accurate. most accurate.

Volcanoes: The Eruptions, The Lava, and The Types

Are all Eruptions Equal?

• A quiet eruption • An explosive eruption

Why are They Different• All magma is not equal• One key factor that controls whether or not an eruption is

quiet or explosive is the amount of trapped gases and water vapor in the magma

Types of MagmasTypes of Magmas- If gases can escape easily, the eruption is quiet. If the gas builds up If gases can escape easily, the eruption is quiet. If the gas builds up

high pressures, it eventually will cause an explosive eruption.high pressures, it eventually will cause an explosive eruption.

- The more trapped water vapor in the magma, the more explosive The more trapped water vapor in the magma, the more explosive the eruptionsthe eruptions

- The second factor is the amount of silica in the magma- The second factor is the amount of silica in the magma

Quiet Eruptions

• Some eruptions, are quiet, with lava slowly oozing from a vent.

• Magma that is relatively low in silica and other fluids is called Basaltic magma and produces quiet eruptions like those on Kilauea (Hawaii)

• Trapped gases and water vapor can easily escape sometimes forming lava fountains

• Quiet eruptions occur over hot spots (Hawaii) and divergent boundaries (Iceland)

Lava FountainOn Russian Island – Basaltic Lava

AlohaSome volcanoes contain lava that can flow like a slow river.

A volcano’s natural beauty will attract many visitors every year

Where Lava Meets the OceanNew land is formed – Hawaii continues to grow

Explosive Eruptions• Some eruptions are very violent, with lava and other

materials being hurled hundreds of miles into the air. Gases from within the earth's interior mix with huge quantities of dust and ash and rise into the air as great, dark, poisonous clouds that can be seen from 100’s of miles away.

• Andesitic magma has more silica than basaltic so it erupts more violently

• Silica-rich or Granitic or Rhyolite magma produces explosive eruptions like those at Soufriere Hills volcano.

• Rhyolite magma is thick and can trap gas and water vapor causing and buildup of pressure

Images from Mt. St. Helens

Photo taken early 1980

Present dayEruption could be felt and

seen hundreds of miles away

Buried in Ash and Mud

Car buried in mud 17 miles away from Mt. St. Helens

Hot ash covered

everything and traveled hundreds of

miles

Escaping the ash on a beautiful afternoon in May

This photo was taken 2 years after the eruption, this once great forest was still trying to recover

Structure of an Eruption

Pyroclastic Flow/Surge

• Hot ash, embers, and poisonous gas

• Maybe 1000 degrees Celsius • Moves very fast 100’s of

meters per second• Moves with great force that

has the ability to knock down trees and small buildings

• Surge can bury, burn, and destroy everything in its path on impact.

• In 1902, Mount Pelee’s surge killed 30,000 people

Red Hot Pyroclastic Cloud with Lightning

Chile, South America

Shield Volcano• A shield volcano is broad with gently sloping sides and

has quiet eruptions like those in Hawaii

• Basaltic lava can also flow through large cracks called fissures forming flood basalts not volcanoes.

• Underwater flood basalts are responsible for creating much of the new seafloor

Cinder Cone Volcano

• A cinder cone volcano has steep sides and is loosely packed

• Its explosive eruptions throw lava and bits of rock high into the air

• Bits of rock or solidified lava dropped from the air are called tephra which ranges in size from ash to large rocks

Paricutin

•On February 20, 1943, Paricutin, a cinder cone volcano, formed from the crevasse in a cornfield and grew to be several hundred meters tall in just a few days. This volcano continued to erupt for 9 years and grew to be over 1300 feet tall.

•This gave modern scientists the opportunity to witness the birth of a volcano

Composite Volcanoes“Stratovolcanoes”

• Some volcanic eruptions can vary between quiet and explosive depending on the trapped gases and silica content.

• Alternating layers of tephra and lava create a composite volcano

• Composite volcanoes mostly occur at convergent boundaries

• Grows to be the tallest volcanoes in the world

Krakatau

•In August of 1883, a composite volcano, Krakatau in Indonesia erupted with such force that the island it was on disappeared, killing more than 36,000 people.

•It launched a series a Tsunamis that devastated the surrounding coastlines.

•It affected the world’s weather and climate for a couple of years.

Balsaltic Lava3 types

• A'aPronounced "ah-ah", this is a basaltic lava that doesn't flow very quickly. It looks like a slowly moving mass of hot Jello, with cool but sharp, rough surface. Once it hardens, the sharp spiny surface of A'a lava is extremely difficult to walk across. These types of lava erupts at temperatures above 1000 to 1100 degrees C.

• PahoehoePronounced "pa-ho-ho", this type of lava is much thinner and less viscous than A'a. It can flow down the slopes of a volcano in vast rivers. The surface of the lava hardens into a thin crust that looks very smooth. Pahoehoe lava can also form lava tubes, where the rock hardens around a fast-moving liquid core. When that core flows out of the tube, a long tunnel remains. Pahoehoe erupts at temperatures of 1100 to 1200 C.

• Pillow LavaPillow lava is typically found erupting from underwater volcano vents. As soon as the lava contacts the water, it's cooled down and forms a hardened shell. As more lava issues from the vent, the shell of lava cracks and more "pillows" come out of these cracks.

ANDESITIC LAVA

• Intermediate SiO2 content (between 52 and 63%)             

• Intermediate viscosity* (does not flow readily)• Andesite magma commonly erupts from stratovolcanoes as thick

lava flows, some reaching several km in length. • Andesite magma can also generate strong explosive eruptions to

form pyroclastic flows and surges and enormous eruption columns. • The word andesite is derived from the Andes Mountains, located

along the western edge of South America, where andesite rock is common.

• Andesite was the main rock type that erupted during the great Krakatau eruption of 1883.

* Viscosity is the resistance to flow

RHYOLITIC LAVA

• Relatively high SiO2 content (above 68%)   

• Relatively high viscosity (flows like wet concrete)

• Rhyolite can look very different, depending on how it erupts. Explosive eruptions of rhyolite create pumice, which is white and full of bubbles. Quieter eruptions of rhyolite often produce obsidian, which is bubble-free and black.

• Some of the United States' largest and most active calderas formed during eruption of rhyolitic magmas (for example, Yellowstone in Wyoming, Long Valley in California and Valles in New Mexico).

• Rhyolite often erupts explosively because its high silica content results in extremely high viscosity which hinders escape of bubbles. When bubbles form, they can cause the magma to explode, fragmenting the rock into pumice and tiny particles of volcanic ash.