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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 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
