
Mystery of the Megaflood


Classroom Activity

Activity Summary
Students
will use everyday items and speeds to describe the dimensions of a massive
flood that occurred in the Pacific Northwest near the end of the last ice age.
Learning Objectives
Students will be able to:
demonstrate how wellknown items can serve as tools for nonstandard
measurement.
calculate length, width, height, and speed of different features related
to the Spokane Flood.
 copy of the "How Big Is That?" student handout
(PDF or
HTML)
 copy of the "The Spokane Flood" student handout
(PDF or
HTML)
 copy of the "Comparison Items List" student handout
(PDF or
HTML)
 calculator
 access to print and Internet resources
Background
A
glacier is a large mass of perennial ice that is formed when snowflakes pack
down and recrystallize as solid ice. Although ice appears as a hard solid,
glaciers flow slowly downslope under their own weight. Like a river, a glacier
picks up and carries rock particles of all sizes. As the glacier moves, the
particles are deposited and accumulated in mounds called moraines. In addition,
glaciers can shrink and grow in response to climate changes. These changes
occur over tens, hundreds, and even thousands of years.
Glaciers exist on all seven continents. About 10 percent of the world's land is
covered with glaciers, most of which are found near the poles. One type of
glacier is found only in polar regions of the world or at high altitudes.
Called polar glaciers, these types of glaciers most often create icebergs,
which are formed when a piece of glacier breaks off to float in the sea. Most
U.S. glaciers are found in Alaska. The Bering Glacier in Alaska qualifies as
North America's longest glacier, measuring 204 kilometers long.
Part I
Large dimensions can be difficult to grasp. Often large dimensions are more
comprehensible when likened to wellknown objects. Students in this activity
will develop ways to represent the dimensions associated with a massive flood
event that took place sometime between 16,000 and 12,000 years ago in what is
now Washington State.
The measurements in this activity are represented in meters. To help
students understand the difference between standard and International System of
Units (SI) measurements, hold up the meter stick and yardstick together. How do
they differ in length? How many meter sticks would reach the ceiling? How many
yardsticks? (Teachers who would like to do the activity in standard units can
have students convert the measurements to standard prior to doing the
activity.)
Next, ask students which distances are easier to imagine:
 275 meters or almost three football fields?
 4,725 kilometers or the distance between New York and San Francisco?
Most students would choose the second measurement in both examples because
those dimensions are more easily visualized than the large numerical
measurement.
Organize the class into teams and provide each team with copies of the
student handouts. Review with students the activity instructions listed on the
"How Big Is That?" handout. Discuss with students why it can be helpful to use
nonstandard forms of measurement to describe something. (It may be easier to
communicate the meaning of a standard measurement through comparison with
commonly known objects.) When should nonstandard forms of measurement be
used? (Nonstandard forms of measurement can be useful when communicating
large measurements to a nonscientific audience.) When are nonstandard
forms of measurement less useful? (Nonstandard forms of measurement are
generally estimates and do not provide the mathematical accuracy that science
often requires.)
First have students categorize the Comparison Items List into the
following five categories: length, height/depth, area, volume, and speed. Then
have students read "The Spokane Flood" description and highlight each of the
measurements within it. Divide up the measurements in the reading among teams
(see Activity Answer for a list of measurements that appear in the
story). Make sure that the same set of measurements is assigned to more
than one team.
Have each team choose items from the Comparison Items List to represent the
team's assigned measurements. Have teams perform the calculations necessary to
create new representations of the measurement in the reading into items they
have chosen from the Comparison Items List.
Help students with calculations as necessary. Converting length,
height/depth, and speed are simple proportions—so many of these equal so
many of those. Students may need assistance converting area and volume,
however. For example, although there are 3 feet in a yard, there are 9 cubic
feet in a cubic yard (3 feet * 3 feet * 3 feet = 9 feet^{3}). Students
may benefit from a brief refresher about finding area and volume:
a = l • w
v = l • w • h
After each team uses the items from the Comparison Items List to create a
new representation of its assigned measurements, have teams that have done the
same measurements from the reading pair off to check their results and discuss
their choices.
Ask all teams to report their equivalent measurements. Discuss and work out
any discrepancies in differing results.
Part II
Hold a class discussion about other comparison items that might be good to use
to bring meaning to the large flood measurements. Record these on the board.
Assign teams items from the newly created class comparison items list.
Have teams use print and Internet resources to find the measurements for the
new comparison items they have been assigned. Then have students convert their
original assigned measurements from the reading to the new comparison items
they have researched.
When all teams have finished, have each team report its representations
using the new comparison items list created by the class. Record unusual or
controversial representations on the board. Once all teams have reported, have
a class discussion about the results. Which ones are most comprehensible? Why?
What are some common features of good analogies?
As an extension, have students research the measurements of the seven
wonders of the ancient world and develop ways to represent them in more
comprehensible terms.
Analogies
can be useful to give meaning to large quantities. How Much Is a
Million?, by David M. Schwartz, is a children's book that explores this
technique. "A billion kids would make a tower that would stand up past the
Moon," is one example from the book. Here are how some of the items from the
Comparison Items List relate to the dimensions in the flood story.
Flood
Dimension

New
Representation

Comparison Item
 
Glacier


height:
762 m

twice
as high as

the
Empire State Building (381 m)
 
Lake Missoula


depth:
610 m

almost
twice as deep as the height of

the
Eiffel Tower (321 m)
 
area:
7,770 sq km

slightly
larger than the area of

Delaware
(6,447 sq km)
 
volume:
2,084 cu km

more
than four times larger than

Lake
Erie (483 cu km)
 
Flood


length
traveled: 842 km

more
than twice the distance from

New
York City to Washington D.C. (386 km)
 
area
covered: 41,440 sq km

almost
half the area of

Maine
(91,700 sq km)
 
height
at tallest: 244 m

almost
one and a half times the height of

the
Washington Monument (170 m)
 
maximum
flow rate: 40 cu km/hr

more
than 350 times the flow rate of

the
1993 Mississippi River flood, peak flow rate (0.11 cu km/hr)
 
Grand Coulee Canyon


length:
80 km

almost
twice the distance of

a
standard marathon race (42.2 km)
 
width:
10 km

almost
four times the length of

San
Francisco's Golden Gate Bridge (2.7 km)
 
height:
274 m

more
than one and a half times as high as

the
Washington Monument (170 m)
 
Dry Falls


height:
107 m

a
stack of about 11

twostory
houses (each 10 m)
 
width:
4.8 km

about
six times wider than

Niagara
Falls (Horseshoe Falls only) (792 m)
 
Camas Prarie Hills


height:
11 m

as
high as

a
common utility pole (11 m)
 
width
between hills: up to 152 m

wider
than six lengthwise

tennis
courts (23.8 m)
 
area:
16 sq km

about
half the size of

Chicago's
O'Hare Airport (28.3 sq km)
 
flood velocity through: 85 km/hr

almost
two and a half times faster than

a
worldclass sprinter (36.9 km/hr)
 
Wallula Gap


daily amount through: 167 cu km

almost
65 times more than the

1993
Mississippi Flood, peak flow rate (0.11 cu km/hr)
 
Web Sites
NOVA—Mystery of the Megaflood
www.pbs.org/nova/megaflood
Read what one geologist has to say about megafloods, discover what Glacial
Lake Missoula was like before it burst,
use an interactive map to explore the scablands, and test your hunches about
the earthly forces that made eight super structures.
A Brief Introduction to the Ice Age Floods
www.iceagefloodsinstitute.org/floods.html
Provides information on how the Pacific Northwest ice floods occurred and
how scientists came to understand what happened, as well as links to additional
resources.
Books
The Channeled Scablands of Eastern Washington
by Paul L. Weis and William L. Newman. Eastern Washington Press, 1989.
Looks at J Harlen Bretz's theory that the scablands were formed by a giant
flood, and Bretz's eventual vindication after years of disbelief by fellow
geologists.
Glacial Lake Missoula and Its Humongous Floods
by David D. Alt. Mountain Press, 2001.
Describes Glacial Lake Missoula and traces the periodic floods' routes
across northern Idaho, the Columbia Plateau, and down the Columbia River to the
Pacific Ocean.
The
"How Big Is That?" activity aligns with the following Principles and Standards
for School Mathematics (see standards.nctm.org/document/index.htm).
Grades 35
Mathematics Standard
Measurement
Grades 68
Mathematics Standard
Measurement
Classroom Activity Author
Developed by James Sammons and WGBH Educational Outreach staff. Sammons has
taught middle and high school science for 30 years. His teaching practices have
been recognized by the National Science Teachers Association, the Soil
Conservation Service, and the National Association of Geoscience Teachers.

