Download Environmental Geology 103 Lab

Introductory Geology
Name _____________________________
_____________________________
_____________________________
_____________________________
Lab 4: How can you recognize a hazardous volcano?
Why are some volcanic eruptions so violent and deadly? Why do some volcanoes spew spectacular fountain
fireworks, but have gentle slopes and gentle eruptions? How can scientists predict whether a volcano will have
deadly eruptions or eruptions that are a bit safer for humans to live near?
In order to understand, predict, and plan for hazards associated with a particular volcano, it is necessary to know
the type of volcano and the composition of the magma. Magma composition plays are primary role in determining
whether the eruption style will be effusive (fluid) or explosive. The eruption type is primarily dictated by the viscosity
(stickiness) of the magma: the greater the viscosity, the more explosive (and more dangerous!) the eruption.
Typically, shield volcanoes are formed by effusive (fluid, flowing) lava eruptions, while composite volcanoes are
formed by explosive pyroclastic eruptions alternating with viscous (sticky) lava flows. By examining the surrounding
volcanic rock, geologists can gain understanding of magma composition and potential hazards associated with a
particular volcano.
Composite Volcano:
Shield Volcano:
(http://dismanibus156.files.wordpress.com/2009/03/pompeii-volcano-eruption.jpg )
(http://kilauealavaflowmount.files.wordpress.com/2008/03/eruption1.jpg)
1
EXPLORING VOLCANOES!
Suppose you have been assigned a job with the Volcanic Hazards Program of the United States Geological Survey
(USGS) and were asked to provide a hazard analysis of several active volcanic locations. What would you need to
know in order to complete your analysis? How would you approach this study? What would you do first?
HELPFUL WEBSITES from your Prelab:
You looked at these websites and others in your Prelab. Refer back to these sites throughout the lab activities as
needed for clarification and information.
Plate Tectonics: http://dsc.discovery.com/video-topics/other/other-topics-volcano-videos.htm
 Key video clips: Plate Tectonics, Lava Flow, Ring of Fire
Volcano formation
http://videos.howstuffworks.com/discovery/29182-assignment-discovery-volcano-basics-video.htm
Volcano shapes
http://science.howstuffworks.com/nature/natural-disasters/volcano6.htm
PART I: HOW CAN YOU TELL A VOLCANO BY THE TYPE OF ROCK?
In order to understand, predict, and plan for hazards associated with a particular volcano, it is necessary to know
the type of volcano (in our case either shield or composite) and the composition of the magma. Magma
composition plays a primary role in determining whether the eruption will be effusive or explosive. Typically shield
volcanoes are formed by effusive mafic lava eruptions while composite volcanoes are formed by explosive
pyroclastic eruptions alternating with sticky felsic lava flows. By examining the surrounding volcanic rock,
geologists can gain understanding of the magma composition and potential hazards. In the following activity your
team will learn how to recognize igneous rocks.
Remove Specimens # 2, 3, 4, 5, 8, 9, 11, 12 from the ROCK drawer.
 Spend some time examining the rocks. Discuss your observations with your team.
 Set aside specimens 4 and 9. We’ll explore them a bit later.
 Group the remaining six rocks in a way that is logical to your team. What were your criteria for your
arrangement? ____________________
 Chances are you split the rocks into two groups based on texture. The fine-grained rocks are volcanic (cooled
extrusively at the surface); the coarse-grained rocks are plutonic (cooled intrusively deep underground). We are
most interested in the volcanic rocks for this exercise, however all igneous rocks are related and it is important to
be familiar with the most common ones.
 Now rank each group from light (felsic) to dark (mafic). You have just sorted the specimens based on
composition!
 Place the rocks in the proper squares on the chart below. This is a visual tool to help you remember the
relationships of the igneous rocks. Include specimens 4 and 9.
 Using Figure 5.7 (page 106) and the instructions given in Exercise 5.7 in your lab manual, determine the names
of the rocks. Complete the chart with rock names and specimen numbers.
 For the volcanic rocks, include the type of volcano (shield or composite).
2
PART I: IGNEOUS ROCK IDENTIFICATION AND CLASSIFICATION Chart
Rock specimens: 2, 3, 4, 5, 8, 9, 11, 12
COMPOSITION
INTERMEDIATE
MAFIC
(low silica content)
Slow cooling rate
Fast cooling rate
FELSIC
(high silica content)
Volcano Type:
Volcano Type:
Volcano Type:
Volcano Type:
Volcano Type:
Volcano Type:
Fast cooling rate
Glassy
COARSE-GRAINED
(Phaneritic)
FINE-GRAINED
(Aphanitic)
TEXTURE
Fast cooling rate
Vesicular
Volcano Type:
Volcano Type:
3
PART II: COMPARING VISCOSITIES OF LAVAS AND THE EFFECT OF SILICA ON VISCOSITY
(adapted from John Farndon "How the Earth Works"
http://volcano.oregonstate.edu/education/vwlessons/lessons/Ch3CM/Handson7Lava.html)
Imagine a THICK COLD MILKSHAKE and a cup of HOT COFFEE. Suppose your 4-yr old cousin comes
to your apartment and knocks over BOTH the milkshake and coffee on your kitchen counter, right next to
your laptop! Which one are you most worried about reaching your laptop FIRST – the COFFEE or the
MILKSHAKE? Why?
The milkshake is THICKER and is more RESISTANT to flowing easily – the milkshake has a HIGHER
VISCOSITY than the coffee.
EXPLORING VISCOSITY
How does the viscosity affect the style of volcanic eruption and types of hazards associated with the
volcano?
With your teammates, you will examine the viscosity of molasses with and without sand. Note the ease
with which each liquid spreads when poured onto a plate.
Plain molasses represents magma with low silica content; molasses mixed with sand represents magma
with high silica content.
Molasses
Silica Content
(High or Low)
Viscosity
(High – very sticky
OR
Low – more fluid)
Eruption Type
(Explosive
OR
Fluid)
Associated
rocks
Volcano
Type
(Shield/
Composite)
Plain
With Sand
1. What affect did the increase in quantity of the sand (silica) have on the viscosity of the molasses
(lava)? ______________________________________________________________________
2. What affect do you think the increased silica would have on the severity of volcanic eruptions and
hazards?
____________________________________________________________________________
PART III: EXPLORE AND BUILD YOUR OWN VIRTUAL VOLCANO!
In this section, YOU will determine how violent or gentle the volcanic eruption! By changing the amounts
of gas and silica composition in the magmas, different types of volcanoes and eruptions are created.
 Go to the website below and explore the site:
 http://news.discovery.com/games/volcano-explorer.htm
 Open the ‘Virtual Volcano’ link to build your own volcano.
 Summarize what happens when you vary the silica and gas concentrations in the magma.
 Describe the type of volcano that forms, the type of eruption created – violent, gentle, etc., the
types of hazards generated, etc.
 Refer back to the chart in Part I to determine the composition (Mafic OR Felsic-to-Intermediate) of
the magma that relates to the degree of silica content.
 Create at least THREE DIFFERENT VOLCANOES.
 Record your observations in the chart below.
4
Type of
volcano
Silica Content
(High OR Low)
Magma Content
(Mafic OR
Felsic-toIntermediate)
Gas Content
Type of
Eruption
(Explosive,
Fluid, etc)
Hazards
(list all shown
with each
eruption)
PART IV: EXPLORING DIFFERENT TYPES OF VOLCANOES
(Portions of this section have been adapted from: Lab Using Volcano Scenarios: Hazard Maps and
Communicating Risk. LeeAnn Srogi, Department of Geology/Astronomy, West Chester University.
http://serc.carleton.edu/NAGTWorkshops/assess/activities/srogi.html)
A. PLATE TECTONICS AND VOLCANO TYPES
You will begin your examination of the shield and composite by viewing the way they are formed. Below
are the websites that have animations illustrating these plate tectonic processes. Please take a few
minutes to watch the animations and answer the following questions.
Animations:
Hot spot volcanoeshttp://www.classzone.com/books/earth_science/terc/content/visualizations/es0904/es0904page01.cfm?ch
apter_no=visualization
Composite volcanoeshttp://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es0902page01.cfm?ch
apter_no=visualization
Fissure Eruptions http://www.classzone.com/books/earth_science/terc/content/visualizations/es0903/es0903page01.cfm?ch
apter_no=visualization
1. Based on the animations, what plate tectonic process was responsible for the formation of composite
volcanoes?
___________________________________________________________________________________
2. Based on the animations, what plate tectonic process was responsible for the formation of shield
volcanoes?
____________________________________________________________________________
3. Based on the animations, what plate tectonic process was responsible for the formation of fissure
eruptions?
____________________________________________________________________________
5
B. DETERMINING VOLCANO TYPES BASED ON SHAPE
Shield and composite volcanoes have different shapes and slopes due to their different magma
compositions. Shield volcanoes have hot fluid magma. Composite volcanoes have relatively cool,
viscous (thick) magma. Because of the very different types of magmas, the resulting shapes and slopes
of the volcanoes are very different.
The ratio of the height of the volcano ÷ the half-width of the base is one way to differentiate between a
shield and composite volcano.
Elevation of summit
Height of volcano = (Elevation of summit) – (elevation of base)
Elevation of base
Half-width of base

A shield volcano has a ratio value less than 0.18, typically about 0.10. This ratio gives the shield
volcano a gentle slope, less than 10° and usually about 5°.

A composite has a higher ratio, greater than 0.18, even as much as 0.25. This gives the composite
a steeper slope, greater than 10° and usually about 15°.
HAWAII
Refer to the HAWAII 3-D topographic map to answer the following questions.
HINT: The material in Chapter 8, Scales on pages 185-187, and Chapter 9: Topographic Maps, pages
190-200, in your lab manual will help with the following questions.
Note: Please DO NOT WRITE on these maps. They are VERY expensive and hard to replace. Thank
you.
1. What is the CONTOUR INTERVAL of the Hawaii 3-D map?
________________feet
2. What is the change in elevation between INDEX CONTOURS for the Hawaii 3-D map?
________________feet
A. Determine the height of the volcano:
 Determine the elevation of the peak.
 Determine the elevation of the base of the volcano.
For Mauna Loa – use the base elevation of ‘0’ – sea level.
 Height of volcano = (elevation of summit) – (elevation of base) = height in feet
3. Height of Mauna Loa
= __________ ft
B. Determine the width of the base:
Use the 3-D map and a ruler to measure the half-width of the volcano base. (NOTE: the base of the
volcano is measured from the point where it begins to noticeably change in elevation from the
surrounding areas)
6

To determine the width of Mauna Loa, measure the distance from Palemano Pt across the
summit to Kapoho Pt.
4. Width of Mauna Loa

= ____________ft
Divide the width of the base in half.
5. Half-width of the volcano base of Mauna Loa
= __________________ ft.
C. Determine the ratio of the HEIGHT OF THE VOLCANO ÷ HALF-WIDTH OF THE BASE.
Show your calculations and work for full credit!!
6. Mauna Loa height/width ratio = ________
7. Mauna Loa is a ___________________________ volcano.
Hawaii :IGNEOUS ROCK SPECIMENS
Refer to your chart from Part I for the following question.
8. Examine the igneous rock associated with shield volcanoes. Determine the NAME and SPECIMEN
NUMBER for the igneous rock specimen. Write the answers in the spaces below.
a.
ROCK NAME
_________________
SPECIMEN #
________
Hawaii :GOOGLE EARTH
We will be using the Google Earth file, Learn about Plate Tectonics. It will need to be downloaded to
your computer from OAKS. You will need to open the Tectonic Plates (simplified boundaries) file.
This week, we are going to view the Volcanoes files, located within the Learn about Plate Tectonic file.
 Download the Learn about Plate Tectonics file, located on OAKS. DO NOT OPEN THE FILE.
 Open Google Earth.
 Look under Places, on the left side of the screen and locate the Learn about Plate Tectonics
file.
 Click on the + next to it to open the file and scroll down until you locate the Tectonic Plates
(simplified boundaries) file.
 Open the Tectonic Plates (simplified boundaries) file by clicking on the + located next to it.
This will activate the files within the Tectonic Plates (simplified boundaries) file.
 Click on the + next to it to open the file and scroll down until you locate the Volcanoes file.
 Open the Volcanoes file by clicking on the + located next to it. This will activate the files within
the Volcanoes file.
 Scroll down the file until you locate the file named: Hawaii and Pacific Ocean. Click on the + to
open the files and click on the box to activate the files within it.
 Scroll down until you locate Hawaiian Islands and open that file by clicking on the +.
 Scroll down until you locate Mauna Loa. Double click on Mauna Loa to zoom to that location.
This will also open a text file containing information about Mauna Loa. Spend some time
zooming in and out and exploring the Mauna Loa volcano. After you have had time to explore
Mauna Loa, go back to the Places file located on the left side of the monitor screen.
 Scroll down until you locate Kilauea. Double click on Kilauea to zoom to that location. Repeat
the procedure above, zooming in and out to learn more about shield volcanoes, their basic shape
and topography.
 Once you have explored the Hawaiian Volcanoes, scroll through the Volcanoes folder until you
locate Africa and Red Sea.
7

Scroll down to the Africa (eastern) file. Open those files by clicking on the +. Scroll down until
you locate the file named The Barrier. Double click on The Barrier to zoom to that location. This
will also open a text file containing information about The Barrier volcanoes. Spend some time
zooming in and out and exploring these volcanoes around the East African Rift zone.
Once you have had a chance to explore both locations, answer the following questions:
1. Describe the basic shape of shield volcanoes:
________________________________________________________________________________
_
2. What type of lava is associated with this type of volcano? __________________________________
3. How does the type of lava (HINT: think viscosity) affect the shape of the volcano?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
MOUNT RAINIER
Refer to the 3-D MAP OF MOUNT RAINIER to answer the following questions.
HINT: The material in Chapter 8, Scales on pages 185-187, and Chapter 9: Topographic Maps, pages
190-200, in your lab manual will help with the following questions.
Note: Please DO NOT WRITE on these maps. They are VERY expensive and hard to replace. Thank
you.
1. What is the CONTOUR INTERVAL of the MOUNT RAINIER map?
___________feet
2. What is the change in elevation between INDEX CONTOURS for the MOUNT RAINIER map?
___________feet
A. Determine the height of the volcano:
 Determine the elevation of the peak.
 Determine the elevation of the base of the volcano. For Mount Rainier base elevation – use
the 2000 ft contour, located on the NW corner of the volcano, near the intersection of the Mowich
River and Rushingwater Creek.

Height of volcano = (elevation of summit) – (elevation of base) = height in feet
3. Height of Mount Rainier
= __________ ft
B. Determine the width of the base:
Use the 3-D map and ruler to measure the half-width of the volcano base. (NOTE: the base of the
volcano is measured from the point where it begins to noticeably change in elevation from the
surrounding areas)

Width of Mount Rainier:
Measure the distance from the 2000 ft contour located on the NW corner of the volcano, near
the intersection of the Mowich River and Rushingwater Creek, and cross over the summit to
the intersection of the Chinook River and Ohanapecosh Rivers, also at 2000 ft.
4. Width of Mount Rainier = ____________ft

Divide the width of the base in half.
5. Half-width of the volcano base of Mount Rainier
= __________________ ft.
8
C. Determine the ratio of the HEIGHT OF THE VOLCANO ÷ HALF-WIDTH OF THE BASE.
Show your calculations and work for full credit!!
6. Mount Rainier height/width ratio = ________
7. Mount Rainier is a ________________________________ volcano.
MOUNT RAINIER: IGNEOUS ROCK SPECIMENS:
Refer to your chart from Part I for the following questions.
8. Examine the igneous rocks associated with composite volcanoes. Determine the NAME and
SPECIMEN NUMBER for each of the igneous rock specimens. Write the answers in the spaces
below.
ROCK NAME
SPECIMEN #
a. _________________
________
b. _________________
________
c.
_________________
________
d. _________________
________
e. _________________
________
Mount Rainier: GOOGLE EARTH
our computer from OAKS. You will need to open the Tectonic Plates (simplified boundaries) file. This
week, we are going to view the Volcanoes files, located within the Learn about Plate Tectonic file.
 Download the Learn about Plate Tectonics file, located on OAKS. DO NOT OPEN THE FILE.
 Open Google Earth.
 Look under Places, on the left side of the screen and locate the Learn about Plate Tectonics
file.
 Click on the + next to it to open the file and scroll down until you locate the Tectonic Plates
(simplified boundaries) file.
 Open the Tectonic Plates (simplified boundaries) file by clicking on the + located next to it.
This will activate the files within the Tectonic Plates (simplified boundaries) file.
 Click on the + next to it to open the file and scroll down until you locate the Volcanoes file.
 Open the Volcanoes file by clicking on the + located next to it. This will activate the files within
the Volcanoes file.
 Scroll down the file until you locate the file named: Canada and Western USA. Click on the + to
open the files and click on the box to activate the files within it.
 Scroll down until you locate USA (Washington) and open that file by clicking on the +.
 Scroll down until you locate Rainier. Double click on Rainier to zoom to that location. This will
also open a text file containing information about Mauna Loa. Spend some time zooming in and
out and exploring the Rainier volcano. After you have had time to explore Rainier, go back to the
Places file located on the left side of the monitor screen.
 Scroll down until you locate St Helen’s. Double click on St Helen’s to zoom to that location.
Repeat the procedure above, zooming in and out to learn more about shield volcanoes, their
basic shape and topography. Pay close attention to the difference in the peak! What happened
here??
 Once you have explored the Washington Volcanoes, scroll back up to locate the Japan folder.
9

Scroll down to the Honshu file. Open those files by clicking on the +. Scroll down until you locate
the file named Fuji. Double click on Fuji to zoom to that location. This will also open a text file
containing information about Fuji. Spend some time zooming in and out and exploring the
volcanoes around Japan and New Zealand.
Once you have had a chance to explore both locations, answer the following questions:
1. Describe the basic shape of composite volcanoes:
________________________________________________________________________________
_
2. What type of lava is associated with this type of volcano? __________________________________
3. How does the type of lava (HINT: think viscosity) affect the shape of the volcano?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
PART V: SUMMARY OF VOLCANOES, HAZARDS, AND PLATE TECTONICS
Rock Specimen #: 2, 3. 4, 5, 8, 9, 11, 12
TEAM INSTRUCTIONS: complete the table below, making sure all team members thoroughly understand
all relationships and concepts.
***CAREFULLY review Figure 5.12 and Table 5.3 on plate boundaries and igneous and volcanic
processes, on page 112 of your lab manual. A review of the animations may be of help.
TYPE OF
VOLCANO
PLATE
SETTING
(Hot Spot/
Mantle or
Convergent)
CRUST TYPE
(Continental or
Oceanic)
MAGMA (ROCK)
COMPOSITION
Felsic-Intermediate
OR Mafic
IGNEOUS
ROCKS
ASSOCIATED
WITH
EACH CRUST
TYPE
TYPES OF VOCANIC
HAZARDS
Basaltic Lava flows,
pyroclastic flows,
lahars, ash fall, etc.
Shield
Composite
Extra Credit: 5 POINTS DUE AT THE BEGINNING OF LAB NEXT WEEK.
You now have all the information needed to complete your concept maps that were provided in the first
lab. A copy is also on OAKS. ALL STUDENTS are to complete a concept map and bring it to lab next
week. It will be collected at the BEGINNING of lab.
CONCEPT MAPS ARE DUE AT THE BEGINNING OF THE LAB PERIOD.
10