1. Volcanoes
March 9, 2011

2. Warm up 3/9/11 What are the three types of plate boundaries?
At which type(s) of boundar(ies) would volcanoes be created?
How are volcanoes and mountains related?

3. 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.

4. 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.

5. 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.

6. 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.

7. Factors Affecting Eruption
Silica – the more silica in lava, the more viscocity it has. A magma’s viscosity is directly related to its silica content.
Gas content - the more gases in lava, the more viscocity it has.
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.

8. Volcanic Material
There are three main types of materials that come out of volcanoes: Lava flows, gases, and pyroclastic material.
Lava flows:
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.

9. 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!

10. Types of Volcanoes Anatomy of a volcano
While there are several different types of volcanoes, each have a “typical” anatomy with the following parts:
Pipe
Vent
Lava
Crater

11. 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.

12. Types of Volcanoes
When you think about a typical volcano, what do you see?
Usually a cinder cone – highly explosive lava.
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!

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

14. Types of Volcanoes
Composite Cones – a large, symmetrical volcano composed of both lava and pyroclastic deposits.
About Composite Cone Volcanoes

15. Composite Volcano
Mt. Shasta

16. Types of Volcanoes
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

17. Shield Volcano
Iceland

18. Check Ins What is the viscosity of a lava/magma?
How does silica content affect viscosity?
How does gas content affect viscosity?
How does temperature affect viscosity?
What are the particles produced in volcanic eruptions called?
Name and describe the 2 types of lava flows.

19. 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.

20. 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?

21. 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

22. Brownie Ticket 3/9 1. A magma’s viscosity is directly related to its:
A. depth B. color C. age D. silica content
2. The particles produced in volcanic eruptions are called ____.
A. laccoliths B. volcanic stocks C. pyroclastic material
D. calderas
3. What type of volcano is built almost entirely from ejected lava fragments?
A. Shield B. Composite Cone C. Cinder Cone

23. Warm up 3/10 Name the three types of volcanoes.
A magma’s _______________is directly related to its silica content.
A lava flow with a surface of rough, jagged blocks and sharp, angular projections what type of flow?
As the temperature of lava increases, the viscocity _______________________.
Highly explosive volcanoes tend to have magma with what three things?
The particles produced in volcanic eruptions are called ________________________.

24. 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!

25. 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.

26. 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.

27. How Volcanoes Form
How Volcanoes Form Video

28. 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.

29. Magma How does rock melt? Heat
There are three factors that contribute to rocks melting, or the formation of magma.
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…

30. Magma 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.

31. Magma
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.

32. 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: __________________________________ __________________________________

33. 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!

34. 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.

35. The Ring of Fire
Watch a slideshow of the Volcanoes on the Ring of Fire HERE!

36. Plate Tectonics and Volcanoes
Plate movement forms volcanoes in three zones:
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).

37. Convergent Boundary Volcano
Was type of convergent boundary caused Mt. St. Helens?
How do you know?
Mount St. Helens emitting volcanic ash 2 months after it’s May eruption in 1980.

38. Plate Tectonics and Volcanoes
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.

39. Plate Tectonics and Volcanoes
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

40. Kilauea, an Intraplate Volcano

41. 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.

42. Brownie Ticket 3/10
Magma tends to rise towards Earth’s surface primarily because:
water is abundant in magma
silica is abundant in magma
rocks become more dense when they melt
rocks become less dense when they melt
Most of the active volcanoes on Earth are located in a belt known as the:
circum-Atlantic belt
Ring of Lava
East African Rift Valley
Ring of Fire
Name at least one of the factors affects the melting point of rock.

43. Warm Up 3/11 Most of the active volcanoes on Earth are located where?
Explain how magma forms.
What three things affect the melting point of a rock?
Why does magma rise to earth’s surface?

44. Announcements Agenda Today: TEST next Friday (a week from today!)
Online Lab
Quiz
TEST next Friday (a week from today!)

45. 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)
You will have 20 minutes to complete this- work efficiently!

46. 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
LOW #2 #3