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Exploring the Formation of Lahars: A Classroom Experiment, Study notes of Construction

An educational experiment designed to help students understand the formation of lahars, or volcanic mudflows, using a small-scale model in a classroom setting. The document also provides background information on lahars, their significance at Mount Rainier, and related vocabulary and skills. Students will learn about the conditions required for lahars to form, the role of water and loose rock, and the impact of lahars on the environment.

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Overview
Explore how small amounts of water can
mobilize loose rock to form lahars by
making a small lahar within the safety of a
beaker or jar and analyzing it using scientific
methods.
Teacher Background
Lahars are fast flowing torrents of rock,
mud, and water
Lahars, also known as volcanic mudflows or
debris flows, are worthy of attention because
they are the principal volcanic hazard in the
valleys that head on Mount Rainier. The
word lahar is an Indonesian term that refers
to any rapidly flowing and gravity-driven
mixture of rock, mud, and water that rushes
down the slopes of a volcano. Lahars have
been known to travel distances of more than
one 100 kilometers (60 miles) at speeds of
60 kilometers per hour (40 miles per hour).
While many scientists treat the terms lahar
and debris flow synonymously, scientists
and officials working at Mount Rainier seek
to reduce confusion locally by modifying
word usage. They reserve the word lahar for
large flows of eruption or landslide origin
with potential to travel to densely populated
valleys, and use debris flow for much
smaller events caused by glacier floods and
precipitation, which stay generally within
park boundaries.
Learner Objectives:
Students wil l:
Recognize lahars as the principal
volcano hazard at Mount Rainier
Become familiar with some of the more
significant lahars that originated on
Mount Rainier
Recognize the role of lava flows,
pyroclastic flows, landslides, and glaciers
that initiate debris flows and lahars
Recognize that an abundance of surface
water and loose, weakened rock makes
Mount Rainier highly susceptible to
lahars and debris flows
Observe how only a small amount of
water is required to initiate a debris flow
or lahar
Become familiar with the nature of
lahars and debris flows, and the proper
usage of the terms
Setting:
classroom
Timeframe:
50 minutes
Grade Level: 610
Lahar in a Jar!
Activi ty last modified: S eptember 5, 2014
1
U.S. Department of the Interior
U.S. Geological Survey
General Information Product 19
Living with a Volcano in Your Backyard
-
An Educator's Guide with Emphasis on
Mount Rainier
Prepared in collaboration with the National Park Service
NATIONAL
PARK
SERVICE
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Partial preview of the text

Download Exploring the Formation of Lahars: A Classroom Experiment and more Study notes Construction in PDF only on Docsity!

Overview

Explore how small amounts of water can

mobilize loose rock to form lahars by

making a small lahar within the safety of a

beaker or jar and analyzing it using scientific

methods.

Teacher Background

Lahars are fast flowing torrents of rock,

mud, and water

Lahars , also known as volcanic mudflows or

debris flows , are worthy of attention because

they are the principal volcanic hazard in the

valleys that head on Mount Rainier. The

word lahar is an Indonesian term that refers

to any rapidly flowing and gravity-driven

mixture of rock, mud, and water that rushes

down the slopes of a volcano. Lahars have

been known to travel distances of more than

one 100 kilometers (60 miles) at speeds of

60 kilometers per hour (40 miles per hour).

While many scientists treat the terms lahar

and debris flow synonymously, scientists

and officials working at Mount Rainier seek

to reduce confusion locally by modifying

word usage. They reserve the word lahar for

large flows of eruption or landslide origin

with potential to travel to densely populated

valleys, and use debris flow for much

smaller events caused by glacier floods and

precipitation, which stay generally within

park boundaries.

Learner Objectives:

Students will:

Recognize lahars as the principal

volcano hazard at Mount Rainier

Become familiar with some of the more

significant lahars that originated on

Mount Rainier

Recognize the role of lava flows,

pyroclastic flows, landslides, and glaciers

that initiate debris flows and lahars

Recognize that an abundance of surface

water and loose, weakened rock makes

Mount Rainier highly susceptible to

lahars and debris flows

Observe how only a small amount of

water is required to initiate a debris flow

or lahar

Become familiar with the nature of

lahars and debris flows, and the proper

usage of the terms

Setting: classroom

Timeframe: 50 minutes

Grade Level: 6– 10

Lahar in a Jar!

Activity last modified: September 5, 2014

U.S. Department of the Interior

U.S. Geological Survey

General Information Product 19

Living with a Volcano in Your Backyard-

An Educator's Guide with Emphasis on

Mount Rainier

Prepared in collaboration with the National Park Service

NATIONAL

PARK

SERVICE

Lahar in a Jar! -continued...

Materials:

100 millileter or larger graduated

cylinder

Wide - mouth 1 liter beaker

Large wooden spoon or paint stirrer

200 to 400 millileters of lahar deposit

or rock debris, as prepared in

accompanying recipe

Calculator

Copies of “Lahar in a Jar” student page

1-meter-long (3 - foot-long) flat board

or gutter

Graphic “Three Prominent Lahars at

Mount Rainier”

Graphic “Mount Rainier and Emmons

Glacier”

Graphic “Extension Maps of Lahar

Hazard Zones”

Graphic “Debris Flow on Tahoma

Creek, 1986”

Graphic “Mount Rainier Lahar

Hazards Zone”

Graphic “Tahoma Creek After Debris

Flow, 1986"

Vocabulary: Beaker, debris flow, flank

collapses, glacier outburst flood, graduated

cylinder, hydrothermal alteration, lahar,

landslide, lava flow, pyroclastic flow

Skills: Observation, record, calculation,

prediction

Benchmarks:

See benchmarks in Introduction.

Once witnessed, lahars and debris flows

are seldom forgotten

The ground shakes and rumbles in a

way similar to that of an approaching

train. Dust plumes rise into the air

above the flow front and small pebbles

splash skyward. The flow, tan or gray

in color, looks and behaves like a river

of flowing concrete. Boulders crush and

grind vegetation, which releases a strong

stench of organic oils that hangs in the

air long after the event is over. Where

valley walls widen, lahars spread, drain

and cease motion. Boulders and trees

that had been buoyed and pushed to flow

margins come to rest as blocky ridges

along the flow’s margin.

The speed of a lahar and debris flow

depends upon its volume and the slope

gradient. Some of the faster flows have

been clocked at speeds of 30 to 60

kilometers per hour (20 to 40 miles per

hour). Lahars may last for hours or days;

debris flows generally last for half an

hour to several hours. Both leave behind

an inhospitable surface of tightly-packed

mud, boulders, and vegetative debris.

Abundant water and rock debris make

Cascade volcanoes highly susceptible to

lahars and debris flows

Eruptions have built vast volcanic slopes

at high elevation that are scattered with

lava fragments and that retain snow and

glacier ice. Mount Rainier’s slopes are

covered by approximately 4.4 cubic

kilometers (1 cubic mile) of snow and

ice, an amount equivalent to that on all

the other Cascade volcanoes combined!

Lahar in a Jar! -continued...

Procedure

What to do Before Class Begins:

◆ Decide if you are going to do a large group demonstration or have the students

work independently or in small groups.

◆ Collect materials.

◆ Make copies of student page Lahar in a Jar.

◆ Prepare to show graphics.

L

a

h

a

r De b

r

i s

Recipe

Lahar in a Jar! -continued...

Some Significant lahars and debris flows at

Mount Rainier

The Osceola Mudflow

A volcanic eruption about 5,600 years ago triggered a flank collapse that removed 3 cubic kilometers (0.

cubic mile) from the summit and eastern flank of Mount Rainier. Because the landslide contained a lot

of water and also picked up snow melt and river water, it transformed into a lahar that rushed down the

White and Nisqually River Valleys as far as northern Puget Sound. In the White River Valley, the lahar

deposited a layer of debris that ranged from approximately one 1 meter (3 feet) to 60 meters (200 feet)

thick, and covered the region now occupied by the communities of Enumclaw, Buckley, Auburn, Kent,

Sumner, and Puyallup. The lahar left behind giant mounds of orange-colored debris that are visible east

of the communities of Enumclaw and Ashford. The Osceola Mudflow is the largest lahar known to have

occurred on Mount Rainier.

The Electron Mudflow

A landslide initiated this mudflow (lahar) around 500 years ago. Weakened rock on the west flank of

Mount Rainier collapsed and slid into the Puyallup River Valley, where it transformed into a lahar that

flowed approximately 100 kilometers (60 miles), all the way to the outskirts of Puyallup and perhaps to

Puget Sound. This lahar deposited sediment as thick as 30 meters (100 feet), and buried the base of trees

in an old growth forest. Construction workers excavating ground for utilities continue to find large logs

and stumps buried by the lahar. There is no conclusive evidence that an eruption triggered the Electron

Mudflow although it may have happened at the onset of or during minor eruptive activity. The Electron

Mudflow reminds us of the possibility that lahars may have noneruption origins.

The National Lahar

The National Lahar is one of the larger lahars formed from the melting of snow and ice during eruptive

activity. This lahar swept down the Nisqually River Valley to the Puget Sound 100 kilometers, (60 miles)

away, between 2,200 and 500 years ago. Between Ashford and the western entrance of Mount Rainier

National Park, it deposited a 3-meter (10-foot) thick layer on the valley floor. Loose rock layers deposited

by the National Lahar look like large boulders set into a matrix of fine-grained material.

Debris flows

Debris flow activity at Mount Rainier has been significant in the valleys of Tahoma Creek, Kautz Creek,

Van Trump Creek, Nisqually River, and the West Fork of the White River, where loose debris has been

deposited during eruptions or left behind from glacier recession. Periods of intense debris flow activity

tend to occur during glacier recession, or when excessive water from rainfall or snowmelt flows across

loose rock deposited by the retreating glacier.

Years of some prominent debris flow events

Tahoma Creek 1967, 1968, 1970, 1971, 1979, 1981, 1986– 2006

Kautz Creek 1947, 1961, 1985, 1986, 2005, 2006

Pyramid Creek 2005, 2006

Van Trump Creek 2001, 2003, 2005, 2006

Nisqually River 1926, 1932, 1934, 1955, 1968, 1970, 1972, 1986

West Fork White River 1987, 2006

Make a lahar in a jar

Learn how only a small amount of water in motion can mobilize loose rock to form a lahar.

Conduct this activity either as a teacher demonstration or in small groups.

1. Divide class into groups of 3 to 4 students.

2. Distribute “ Lahar in a Jar ” student page.

3. Instruct students to place approximately 400 milliliters of loose lahar material from recipe

sample onto a large piece of paper and break up any large clumps of dirt and debris. Dump

the loose rock into a beaker. Press it firmly with your hands to remove spaces from

between the particles. Record the exact volume on the student page.

4. Ask students to predict how much water they think is required to make the deposit flow

like a lahar. 10 ml? 100 ml? More? Students record their prediction on the student

activity sheet.

5. Fill the graduated cylinder with water and record the starting amount of water on the

student page.

6. Instruct the students to begin pouring water in the beaker in increments of 10 ml.

7. Students should stir the loose rock after each addition of water.

8. After each addition of water, students should tilt the beaker to the side and gently rotate

it sideways to determine if the mixture “flows” around the jar sides as a lahar would.

The consistency initially is like that of dry dirt, but with the addition of water, changes

to the consistency of cookie dough and later to that of thick cake batter. Decrease the

amount of water added each time as your lahar begins to flow. Remember, it does not take

much water to get debris flowing.

9. Students sum the amount of water used after the rock debris forms a lahar in the jar and

record the amount on the student page.

10. Instruct students to compare the total volume of lahar and water and determine the

percent water required to produce a lahar in a jar. Ask whether the amount of water was

as predicted. Answer: will probably be between 20 to 40 percent, depending on the

material used. At Cascade Volcanoes, the water content in debris flows and lahars is

generally between 30 and 45 percent.

Lahar in a Jar! -continued...

11. Each student group should pour their lahar onto the inclined gutter or board for all of

the class to see. Ask for hypotheses about what happens when slope of the gutter or

board is changed, then test the hypotheses. Inquire about any interesting observations

made of the lahar mixture. The lahar may flow in single or multiple surges. Velocity

of the flow increases with slope.

12. Ask students to follow the path of energy transformation, and to write about this, or

draw a diagram on the reverse side of their student pages. Students should report

that the lahar while still in the jar has potential energy. Kinetic energy is released

as the lahar slides down the gutter or board.

13. Ask students what conditions exist on Cascade volcanoes that promote development

of lahars. Answers: Loose rock, abundant water, steep slopes, heat.

Adaptations

◆ Provide students with sand, clay, garden soil and gravel and instruct them to

hypothesize about what happens when the amount of clay is increased and

decreased. Instruct students to design and conduct experiments with different

proportions of materials.

◆ Obtain rock debris from other sources in your community, such as streambeds,

lahar deposits, gardens, etc., and repeat Lahar in a Jar again. Compare results with

your lahar recipe mixture.

Extensions

◆ Instruct students to draw a diagram and (or) a flow chart that illustrates the initiation

and activity of lahars and debris flows.

◆ Use library and Internet searches to learn more about the lahar history of Mount

Rainier and the other snow-clad volcanoes of the Cascades.

◆ This experiment does not account for the porosity (air space between the particles)

of the solids. Instruct students to design an experiment that accounts for porosity.

Lahar in a Jar! -continued...

Walder, J.S., and Driedger, C.L., 1994, Frequent outburst floods from South Tahoma

Glacier, Mount Rainier, USA: relation to debris flow, meteorological origin

and implications for subglacial hydrology: Journal of Glaciology,

v. 41, no. 137, pp. 1 10.

Walder, J.S., and Driedger, C.L., 1993, Glacier-generated debris flows at Mount Rainier:

U.S. Geological Survey Fact Sheet, Open-File Report 93 124, 2 p.

Zehfuss, P.H., Atwater, B.F., Vallance, J.W., Brenniman, H., and Brown, T.A., 2003,

Holocene lahars and their by-products along the historical path of the White River

between Mount Rainier and Seattle: in Swanson, T.W., ed, Western Cordillera and

adjacent areas: Boulder, Colorado, Geological Society of America Field Guide 4,

p. 209 223.

Lahar in a Jar! -continued...

Refer to Internet Resources Page for a list of resources available as a supplement

to this activity.

Photo Credits

1. Mount Rainier and Emmons Glacier, Photo by Carolyn Driedger, USGS. 2. Debris Flow on Tahoma Creek on July 26, 1988, Photo by G.G. Parker, USGS. 3. Tahoma Creek after Debris Flows, 1988, Photo by Carolyn Driedger, USGS.

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

Instructions: Follow the procedures below to make a small lahar in a jar. You will mix known

volumes of rock debris and water. Give your mixed lahar a run down a gutter or board provided by

your teacher.

Lahar in a Jar

1. Place approximately 200 to 400 milliliters of “lahar” into a beaker. Break up any large

clumps of dirt and debris. Record the exact volume here.

2. Make a prediction. How much water will be necessary to set the

rock debris sample into motion as a small, in-the-jar lahar?

10 ml? 100 ml? Record your prediction.

3. During this experiment, you will pour water into the

beaker repeatedly, in increments of approximately

10 ml. In the space below, develop a procedure for keeping

track of the amount of water that you tip during successive pours. Note: You

may need to fill the graduated cylinder more than once during this experiment.

4. Pour water into the beaker in increments of approximately 10 ml. Stir the lahar rocks

and water with a spoon or a stick after each addition of water. Tilt the beaker and

gently rotate it sideways to observe if the mixture “flows” around the jar sides as a

lahar would move. Repeat as much as necessary, and test for flowing. When the

mixture begins to flow, STOP! Add no more water! Note that the mixture first

appeared as dry dirt, but with the addition of water, has changed to the consistency

of cookie dough and now resembles thick cake batter.

1. Place approximately 400 milliliters of “lahar” into a beaker.

Break up any large clumps of dirt and debris. Record the exact

volume here.

ANSWER:

400 ml

2. Make a prediction. How much water will be

necessary to set the rock debris sample into

motion as a small, in-the-jar lahar? 10 ml?

100 ml? Record your prediction.

ANSWER:

20 ml in this trial run

3. During this experiment, you will pour water

into the beaker repeatedly, in increments of approximately 10 ml. In the

space below, develop a procedure for keeping track of the amount of water

that you tip during successive pours. Note: You may need to fill

the graduated cylinder more than once during this experiment.

Students might choose to keep track of water increments added, or subtract the final

reading from the top reading. Students will need to fill the graduated cylinder more

than once during this experiment.

4. Pour water into the beaker in increments of approximately 10 ml. Stir the lahar rocks and

water with a spoon or a stick after each addition of water. Tilt the beaker and gently rotate

it sideways to observe if the mixture “flows” around the jar sides as a lahar would move.

Repeat as much as necessary, and test for flowing. When the mixture begins to flow,

STOP! Add no more water! Note that the mixture first appeared as dry dirt, but with the

addition of water, has changed to the consistency of cookie dough and now resembles

thick cake batter.

In this trial run, we added 130ml of water before the mixture began to “flow” when

the beaker was rotated.

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

Instructions: Follow the procedures below to make a small lahar in a jar. You will mix known

volumes of rock debris and water. Give your mixed lahar a run down a gutter or board provided

by your teacher. Answers provided on the teacher page are derived from a trial run with the

mixture of lahar material noted in the lahar recipe. Answers will vary, depending upon

your sample’s clay content, compaction, density, and moisture content.

Lahar in a Jar Answers

5. Compare the total volume of water to the cumulative volume of lahar rocks and water.

Use the space below to calculate the percent water required to form a lahar in the

beaker. Record your result here.

ANSWER:

25 percent water but answer will range from 20 to 40 percent

6. Determine whether the actual percent of water required to make a lahar is more or less

than your prediction.

ANSWER:

In this trial run, the actual value exceeded the predicted value.

7. After completion of this experiment, preserve your sample for its run down a gutter or

board as provided by your teacher. Explain why the slopes of Cascade volcanoes are an

ideal location for the development of debris flows and lahars.

ANSWER:

There is an abundance of surface water and

loose volcanic rocks on the steep slopes

of Cascade stratovolcanoes.

8. Describe or draw a diagram of the energy

transformations that happen as a lahar

rushes down the flanks of a volcano and

comes to rest.

ANSWER:

The rock debris embedded within riverbeds

and embankments holds potential energy

Kinetic energy is released as the debris flow

or lahar mobilizes the rock debris and

carries it down valley.

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

Lahar in a Jar Answers

continued

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

Thre e Prom i n e nt L a hars M a p

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

M a p of L a har Ha z ard Zo n e s

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

De b r i s Fl ow o n Ta hom a Cre e k, 1988

Photo by G.G. Parker, USGS

Living with a Volcano in Your Backyard–An Educator's Guide: U. S. Geological Survey GIP 19

Ta hom a Cre e k Af t e r De b r i s Fl ows, 1988

Photo by Carolyn Driedger, USGS