VolcanoesMarch 9, 2011

Warm up 3/9/11

1. What are the three types of plate boundaries?

2. At which type(s) of boundar(ies) would volcanoes be created?

3. How are volcanoes and mountains related?

Objectives

• I will be able to identify what makes a volcanic eruption explosive.

• I will be able to compare materials that come out of a volcano.

• I will be able to compare the different types of volcanoes.

Key Points• A magma’s viscosity is directly related to its silica content.• A lava flow with a surface of rough, jagged blocks and sharp,

angular projections is called aa flow.• As the temperature of lava increases, the viscocity decreases.• Highly explosive volcanoes tend to have magma with high silica,

high viscosity, and higher gas content.• The particles produced in volcanic eruptions are called

pyroclastic material.• Pyroclastic materials include ash, cinders and lapili.• The most abundant gas associated with volcanic activity is

water vapor.• A cinder cone is a type of volcano that is built almost entirely

from ejected lava fragments.• The pipe is the hollow center of the volcano.

Factors Affecting Eruption

• Volcanoes can erupt explosively or mildly. They can erupt with lots of lava spewing out or slowly oozing out of the mouth. Some volcanoes erupt ash and dust with no lava at all. So what makes all of them so unique?

• Let's watch!• Let’s take a look at the factors that affect the

eruption of a volcano.

Factors Affecting Eruption

Viscocity - a substance’s resistance to flow. – This means that something that has a high

viscosity does not flow easily. A substance with a high viscosity would be honey. A substance with a low viscosity would be water.

– If the lava of a volcano has high viscocity, the eruption of a volcano will be highly explosive.

– There are three factors that affect the viscocity of lava: silica content, gas content, and temperature.

Factors Affecting Eruption1. Silica – the more silica in lava, the more viscocity it

has. A magma’s viscosity is directly related to its silica content.

2. Gas content - the more gases in lava, the more viscocity it has.

3. Temperature – as temperature in lava increases, the viscocity decreases. • Example: heating up syrup.

***Bottom line: Highly explosive volcanoes tend to have magma with high silica, high viscosity, and

higher gas content.

Volcanic MaterialThere are three main types of materials that come out of volcanoes: Lava flows, gases, and pyroclastic material.Lava flows: 1.aa flow (AH ah): A lava flow with a surface of rough, jagged blocks and sharp, angular projections. view here! Think “ow!” it hurts to step on!•pahoehoe flow: lava flows that flow slowly forming flows that look like twisted braids in ropes.

view here!Gases:The most abundant gas associated with volcanic activity is water vapor.

Volcanic Material

Pyroclastic Material – the particles produced in volcanic eruptions.

• Pyroclastic materials include ash, cinders and lapili.

• These particles can range in size from fine dust to pieces that weigh several tons!

Types of VolcanoesAnatomy of a volcano• While there are several different types of

volcanoes, each have a “typical” anatomy with the following parts:

A. PipeB. VentC. LavaD.Crater

Types of Volcanoes

• The three main types of volcanoes are cinder cones, shield volcanoes and composite cones.

• Magma composition plays a major part in determining the form of a volcano.

Types of Volcanoes

• When you think about a typical volcano, what do you see?

• Usually a cinder cone – highly explosive lava.1.A cinder cone is a type of volcano that is built

almost entirely from ejected lava fragments.– This give it a cone shape over time.– Learn more here!

Cinder Cone Volcano

Cinder Cone from Pu'u'O'o eruption of Mount Kilauea

Types of Volcanoes

2. Composite Cones – a large, symmetrical volcano composed of both lava and pyroclastic deposits.

About Composite Cone Volcanoes

Composite Volcano

Mt. Shasta

Types of Volcanoes

3. Shield Volcano – have the shape of a broad, slightly domed structure.

• Most shield volcanoes grow up from the ocean floor – like the islands of Hawaii or Iceland.

More about shield volcanoes

Shield Volcano

Iceland

Check Ins

1. What is the viscosity of a lava/magma?2. How does silica content affect viscosity?3. How does gas content affect viscosity?4. How does temperature affect viscosity?5. What are the particles produced in volcanic

eruptions called?6. Name and describe the 2 types of lava flows.

CHECK-IN

• Answer the check-in questions in COMPLETE SENTENCES on a separate sheet of paper.

• Your check-in questions for this whole unit will be collected and taken as a quiz grade.

• These will also be THE BEST thing for you to study before your next quizzes/tests.

Help me help you…

• For a quiz grade…• In general, what would you like to see

more/less of in class– Think about your favorite teacher you’ve had-

What did they do that you liked?– Think about your favorite core subject- what did

you really enjoy about that class that can be applied to Earth Science?

VOCABULARY• Your vocabulary is due on Monday• Use this time wisely to work• REMEMBER you need

–The definition–The source for the definition (where

you got it)–The definition in your own words

Brownie Ticket 3/9

1. A magma’s viscosity is directly related to its: A. depth B. color C. age D. silica content2. The particles produced in volcanic eruptions

are called ____.A. laccoliths B. volcanic stocks C. pyroclastic materialD. calderas3. What type of volcano is built almost entirely

from ejected lava fragments?A. Shield B. Composite Cone C. Cinder Cone

Warm up 3/101. Name the three types of volcanoes.2. A magma’s _______________is directly related to

its silica content.3. A lava flow with a surface of rough, jagged blocks

and sharp, angular projections what type of flow?4. As the temperature of lava increases, the viscocity

_______________________.5. Highly explosive volcanoes tend to have magma

with what three things?6. The particles produced in volcanic eruptions are

called ________________________.

Announcements• We will have a QUIZ tomorrow on Volcanoes!

• Vocabulary for Chapters 8 and 10 are due MONDAY!

• Remember, this is the time to make a NEW start and get a good grade for this new report card!

Objectives

• I will be able to relate plate tectonics to volcanoes by describing where magma comes from, the types of boundaries that produce volcanoes.

• I will be able to graph the locations of volcanoes on a map and compare patterns of volcanoes to plate tectonics.

Key Points• Magma composition plays a major part in

determining the form of a volcano.• Magma forms when solid rock in the crust and

upper mantle melts.• The composition of the material, water content

and confining pressure are factors that affect the melting point of rock.

• Magma tends to rise towards Earth’s surface primarily because rocks become less dense when they melt.

• Most of the active volcanoes on Earth are located in a belt known as the ring of fire.

• Identify an O-C plate boundary creating a volcano.

How Volcanoes Form

• How Volcanoes Form Video

Magma

• As we know, magma composition plays a major part in determining the form of a volcano.

• But where does magma come from?• Magma forms when solid rock in the crust and

upper mantle melts.

Magma• How does rock melt?

– There are three factors that contribute to rocks melting, or the formation of magma.

1. Heat– As you go deeper in the earth, the temperature rises.– Subduction creates friction and causing heat– As magma rises, it heats rocks closer to the earth’s

surface.• But this alone is not enough to create all of the

magma that we know exists below the earth’s crust…

Magma

2. Confining Pressure– As confining pressure is decreased, the melting

temperature of rocks is lowered.– This means that as rocks can melt easier as they

are released from the confining pressure deep within the earth.

– This process is called decompression melting.

Magma

3. Water Content– Water in rocks can cause a rock to melt at lower

temperatures.– Rocks with more water in them melt easier than rocks

that are “dry”.

• BOTTOM LINE: The composition of the material, water content and confining pressure are factors that affect the melting point of rock.

Magma

• Now that we know how magma forms, why does it come to the surface of the planet?

• Let’s discuss.• Write down what you think:

__________________________________ __________________________________

Magma

• Magma tends to rise towards Earth’s surface primarily because rocks become less dense when they melt.

• What does that mean? When rocks change from a solid state to a liquid state, they become lighter!

• What is lighter will rise, just like heavy things sink!

Plate Tectonics and Volcanoes

• Most of the active volcanoes on Earth are located in a belt known as “The Ring of Fire”.

• Others are located seemingly sporadically around the globe.

• Scientists could not explain the worldwide distribution of volcanoes until the introduction of the theory of Plate Tectonics.

The Ring of Fire

• Watch a slideshow of the Volcanoes on the Ring of Fire HERE!

Plate Tectonics and Volcanoes• Plate movement forms volcanoes in three zones:1.Convergent Plates

– Ocean – Ocean• Rising magma can form volcanic island arcs in an

ocean (Aleutian Islands).

– Ocean – Continent• Rising magma can form continental volcanic arcs

(Andes Mountains).

Convergent Boundary Volcano

Mount St. Helens emitting volcanic ash 2 months after it’s May eruption in 1980.

Was type of convergent boundary caused Mt. St. Helens?

How do you know?

Plate Tectonics and Volcanoes2. Divergent Plate Boundaries

– When plates pull apart, there is less pressure on the rocks below.

– Because of the decrease in pressure, rocks melt and magma is formed.

Plate Tectonics and Volcanoes3. Intraplate Igneous Activity

– Intraplate means activity inside a tectonic plate away from plate boundaries.

– This is caused by Hot spots. – Examples of this are the Hawaiian Islands

Kilauea, an Intraplate Volcano

Mapping Volcanoes Lab

Follow the directions on the handout to map volcanoes around the world.

After you finish plotting the volcanoes, answer the questions in complete sentences.

Brownie Ticket 3/101. Magma tends to rise towards Earth’s surface

primarily because:A. water is abundant in magmaB. silica is abundant in magmaC. rocks become more dense when they meltD. rocks become less dense when they melt

2. Most of the active volcanoes on Earth are located in a belt known as the:A. circum-Atlantic beltB. Ring of LavaC. East African Rift ValleyD. Ring of Fire

3. Name at least one of the factors affects the melting point of rock.

Warm Up 3/11

1. Most of the active volcanoes on Earth are located where?

2. Explain how magma forms.

3. What three things affect the melting point of a rock?

4. Why does magma rise to earth’s surface?

Announcements

• Agenda Today: – Online Lab– Quiz

• TEST next Friday (a week from today!)

Viscocity Lab

• You will be working in pairs to investigate viscosity today.• 1 partner and ONLY 1 partner will need his or her laptop

out.• Once you are in your groups go to the following web

address (also linked on the wiki)

• http://www.seed.slb.com/flash/science/lab/liquids/visco_exp/en/viscosity.htm?width=620&height=500&popup=true

• You will have 20 minutes to complete this- work efficiently!

Quiz - #16 16. RANK the following samples of magma from

LOWEST to HIGHEST viscocity using the chart below: (write the red and fill in the blanks)

Lowest Viscocity: _____________________Middle Viscocity: _____________________Highest Viscocity: _____________________

Magma Sample:

GAS SILICA TEMPERATURE

#1 HIGH HIGH LOW

#2 HIGH LOW LOW

#3 LOW LOW HIGH