Topic: volcanoes and Volcanoes Locations

• Objectives:

– I will understand what a volcano is and how it is formed

– I will understand the 3 locations where volcanoes form at

Volcanoes and You

• A volcano is an opening in the earth’s surface that often forms a mountain when layers of lava and ash build up over time

What is a Volcano?

• A volcano is an opening in the earth’s surface that often forms a mountain as ____of lava and ash build up

over time

Answer Bankapart

constantrises

collidelayers

Magma Rising• How does magma make it

to the surface?• Magma is hotter, lighter

and less dense than the rock around it

• This process is similar to a lava lamp

• Therefore, it slowly makes its way upward toward the earth’s surface

• Eventually it finally makes it’s way to the surface exiting a volcano

How does Magma make it to the Earth’s surface?

• Because it is hotter and less dense, therefore it _____ up to the surface exiting a volcano

Answer Bankapart

constantrises

collidelayers

Volcano Locations

• Volcanoes form at:- Divergent plate boundaries Here plates pull apart as new magma rises

(Ex—Iceland)- Convergent plate boundaries

Here plates collide and one plate subducts where it melts feeding volcanoes at the surface

(Ex—Mt. St. Helens WA)-Hot spots

Here a constant steady flow of magma rises to the surface to form volcanoes

(Ex—Hawaii)

Volcano Locations

• Volcanoes form at:- Divergent plate boundaries Here plates pull apart as new magma rises

(Ex—Iceland)

Divergent Plate Boundary:Spreading Iceland apart

Iceland Hot Springs

Volcano Locations

• Volcanoes form at:- Convergent plate boundaries

Here plates collide & one plate subducts where it melts feeding volcanoes at the surface (Ex—Mt. St. Helens)

Cascade Volcanoes

• From Northern California up to Canada lies a series of volcanoes called the Cascade Mountain Range

• Here the Juan de fuca plate subducts under the north American plate forming a series of volcanoes that stretch form Northern California Up to Canada

• As the Juan de fuca plate subducts, it melts, feeding the volcanoes at the surface

Mount St. Helens

• In 1980, Mt. Saint Helens erupted in the state of Washington

• It was one of the largest recent volcanic eruptions in North America

• Geologists warned people to leave, but despite this, 63 people lost their lives from this eruption

• Heat from the eruption caused snow to melt, creating major floods

The Re-Birth of Mt. Saint Helens

Shockwave blast blew the trees down like toothpicks!

Which way was the blast coming from?Trees behind the mountain were spared

Where did all that ash go?

Volcano Locations

• Volcanoes form at:- Hot Spots

Here a constant steady flow of magma rises to the surface to form volcanoes(Ex—Hawaii)

Hot Spots

Lithospheric Plate

Ocean

• Hawaii formed as the Pacific plate slowly moved over a Hot Spot

• Over Ten Million Years, A chain of Islands formed

Stationary Hot Spot

Where are the 3 locations volcanoes form?

- Divergent plate boundaries Here plates pull _____ as new magma rises

(Ex—Iceland)

- Convergent plate boundaries Here plates _____ and one plate subducts

where

it melts feeding volcanoes at the surface (Ex—Mt. St. Helens WA)

-Hot spots Here a ____steady flow of magma rises to the

surface to form volcanoes (Ex—Hawaii)

Answer Bankapart

constantrises

collidelayers

= Volcanoes

Ring of Fire

• Convergent plate boundaries are located all around the Pacific Rim

• Because of this, volcanoes are located all around the Pacific Ocean

• These volcanoes make up the Ring of Fire

What is the Ring of Fire?

• A chain or ring of volcanoes ____ the pacific ocean created by convergent boundaries

Answer Bankapart

constantrises

Collidearoundlayers

Volcanoes Form at:

_______ Plate Boundaries

Hot ____Divergent Plate

Boundaries

Plates____as magma

rises Plates collide Feeding volcanic

______ above

______ flow of magma to the surface

Answer BankConvergent

Spotsconstant

mountainsspread

Summarize:

Topic: Magma Composition

• Objectives:

– To understand how magma composition effects whether a volcano will erupt violently or quietly

– To understand how silica effects the viscosity or thickness of magma

2 Types of Eruptions

• Some volcanic eruptions are explosive, & violent and while others are non-explosive erupting quietly

• For example, Mt. Saint Helens erupt violently (explosive)

• Kilauea in Hawaii erupts quietly (non-explosive)

Explosive!

Non-Explosive

What are the 2 types of Volcanic Eruptions?

-Explosive, ____eruptions: (Ex: Mt. Saint Helens)

-Non-Explosive, _____ eruptions (Ex: Kilauea)

Answer BankTrapssilicaQuiet

Releasesgasesviolent

Magma Composition

• Why do some volcanoes erupt explosively and others non-explosively?

• It has to do with 3 factors:-the amount of trapped gases in the magma

-viscosity or thickness of the magma

-silica content

Rhyolitic Magma = Explosive Eruptions

Basaltic Magma = Non-Explosive Eruptions

What factors make volcanoes explosive?

• The amount of trapped ____

the magma• Viscosity or thickness of magma• _____ content

Answer BankTrapssilicaQuiet

Releasesgasesviolent

Magma Composition

•Rhyolitic Felsic magma is high in silica, therefore it has a high viscosity (thick) and traps gases producing violent explosive eruptions

•Basaltic Mafic (dark

color) magma is low in silica, therefore it has a low viscosity and releases gases producing quiet non-explosive eruptions

Rhyolitic Magma = Explosive Eruptions

Basaltic Magma = Non-Explosive Eruptions

What is the difference between Rhyolitic and Basaltic magma?

• Rhyolitic magma: – High in silica – High Viscosity (thick)– ____gases (increasing pressure)– creates violent, explosive

eruptions• Basaltic magma:

– Low in silica– Low Viscosity (Very fluid)– _____gas (reducing pressure)– creates quiet, non-Explosive

eruptions

Answer BankTrapssilicaQuiet

Releasesgasesviolent

Magma Link

• http://dsc.discovery.com/convergence/pompeii/interactive/interactive.html

Who has been listening?Which one has the most silica?Which one has the least silica?

Basaltic Rhyolitic

Which magmatraps gases?

Which magma Releases gases?

Which magma contains more silica?

Silica Silica

Summarize!

Explosive Eruptions?

High in Silica?

Traps gases?

High or low Viscosity?

Example

Rhyolitic

___ Yes ___ ____ Viscosity

Mt. St. Helens

Basaltic

___ No ___ ____Viscosity

KilaueaHawaii

• Magma high in _____ is _____ giving it a high viscosity therefore trapping gases

• Magma low in silica is _____ giving it a ____viscosity therefore releasing gases

Answer BankThickHighsilica

viscosityYes(2)Fluidlow

No(2)

Topic: Volcano Types

• Objectives:

– To understand the differences between the 3 major types of volcanoes

– To understand how magma affects the shape and steepness of a volcano

Forms of Volcanoes

• There are three basic types:– Cinder Cone Volcano– Composite Volcano– Shield Volcano

What are the 3 types of Volcanoes?

– Cinder Cone Volcano– Composite Volcano– Shield Volcano

Cinder ConeCinder Cone

Layers of Ash and Cinder

Volcanic Bombs

Pipe

-Smallest type-Steep slopes-Made by layers of Ash and Cinder

-Example: Paracutin, Mexico

3,000m

Paricutin Cinder Cone, Mexico

Sunset Crater

Cinder Cone,Arizona, USA

What is a Cinder What is a Cinder Cone Volcano?Cone Volcano?

Layers of Ash and Cinder

Volcanic Bombs

Pipe

-____ in size-Made of layers Cinder (hot rock) and ash which produce _____slopesEx. Paracutin Mexico

3,000m

Answer BankFlat

Steepmassive

small

Composite Cone

-Composite cones are built up by layers of Ash and thick rhyolitic lava -High viscosity magma traps gases therefore they erupt with great explosive & violent power-Thick rhyolitic magma produces moderately Steep slopes-Example: Mount Saint Helens

Smallcone

Dyke

Crater

Lava Layer Flank eruption

LavaFlow

Crust

Pyroclastic Flow

Mt. Saint Helens,Composite Volcano,

Washington, USA

Mt. Fuji, Composite Volcano, Japan

What is ACompositeVolcano?

-Volcano Made of layers Ash, and _____(thick) lava which produce moderately steep slopes-Thick, ____viscosity magma traps gases producing very explosive & violent eruptionsEx. Mt. St. Helens

Smallcone

Dyke

Crater

Ash layer

Lava Layer Flank eruption

LavaFlow

Crust

Pyroclastic Flow

Answer basalticRhyolitic

Highlow

Shield Volcano-Shield Volcanoes are massive volcanoes built up only from layers of basaltic (fluid) lava giving them a flat gentle sloping shape

-Low viscosity magma releases gases producing quiet, non-explosive eruptions

-Ex: Big Island of Hawaii, USA and Olympus Mons, Mars

250 miles wide!

10,000m

Composite volcano to scale

Layers of Lava Lava Flow

Big Island Hawaii, USA

Big Island, Hawaii

Olympus Mons & Arizona?

Is it steep? Or not steep? Why?

What is a Shield Volcano?

-Shield Volcanoes are ______ volcanoes built up only from layers of ______ (fluid) lava giving them a flat gentle sloping shape

-_____ viscosity magma _____ gases producing quiet, non-explosive eruptions

-Ex: Big Island of Hawaii, USA

250 miles wide!

10,000m

Composite volcano to scale

Layers of Lava Lava Flow

AnswerBanksmall

massivebasalticreleases

low

• http://almandine.geol.wwu.edu/~dave/courses/2008/fall/101/lectures/media/Lecture07/VolcanoTypes.swf

Review-Where is a Cinder Cone Volcano?-Where is a Composite Volcano-Where is a Shield Volcano-Which volcano erupts explosively?-Which 2 volcanoes have steep sides?-Which volcano is made of layers of lava,

producing flat sides

A

BC

Cinder Cone

Composite cone

Shield

-____ in size-made of layers Cinder (hot rock) and ash-SteepEx. Paracutin Mexico

-____ in sizeMade of layers Ash and _____ (thick) magma producing ____slopes- High viscosity magma traps gases producing very___& __ eruptions

Ex. Mt. St. Helens

-____ in size-made of layers of _____ (fluid) lava producing flat gentle slopes-Low viscosity magma releases gases producing non-explosive & ____ eruptions-Ex. Big island Hawaii

Summarize:Summarize: please draw table

Answer Bank

RhyoliticModerate(2)

violentSmall

basalticExplosive

quietmassive

Shield

Composite Cinder Cone