The student will:
- Identify the course of the Firehole River
on a map of Yellowstone National Park and list,
in writing, at least two locations through which
the river passes.
- List, in writing, at least two ways in which
the river might be affected when it flows through
the park’s geyser basins.
- Participate in a demonstration of a geyser
- Examine and measure changes in the temperature
and acidity of a water sample when infusions
of water and baking soda are added.
- Calculate with 100% accuracy the conversion
of at least 2 temperatures from Fahrenheit to
Celsius, or vice versa.
A - Map of Yellowstone National Park (1.4MB
B - Firehole in the Classroom Worksheet (13KB
Glass container able to tolerate hot water
1 cup and ¼ cup measuring cups
Cold water (for best results, refrigerate night
Hot water (may be heated in an electric teapot
or hot plate or previously
warmed and stored in a thermos)
Thermometer (preferably one in which temperature
can be measured in both
Fahrenheit and Celsius)
Film canister with small hole punched in the canister’s
Antacid tablet such as Alka Seltzer
Litmus paper with pH chart
During this lesson plan, students should practice
converting temperature readings from Fahrenheit
to Celsius or vice versa.
To convert a Fahrenheit temperature into Celsius:
32 from the Fahrenheit temperature
the answer of Step A by 9
the answer of Step B by 5
Or: TempC=(TempF-32) x 5/9
To convert a Celsius temperature into Fahrenheit:
the Celsius temperature by 9
the answer of Step A by 5
C) Add 32
to the answer of Step B
Or: TempF=(9/5 x TempC)+32
The Firehole River begins at tiny Madison Lake
in the southwestern corner of Yellowstone National
Park, and flows down the north-facing slopes of
the continental divide. During the first ten miles
of its course, the Firehole River has a temperature
of approximately 54°F (12°C) and a pH
of 7.4, readings which are consistent with the
temperature and pH of many other natural Rocky
The character of the river changes dramatically
when it passes through 3 major geyser basins:
the Upper Geyser Basin, Midway Geyser Basin, and
the Lower Geyser Basin. By the time the river
has completed the 16 mile stretch between the
Upper Geyser Basin and Madison Junction, nearly
a quarter of its water comes from hydrothermal
sources. The river’s temperature increases
to a maximum of 79°F (26°C). Its pH increases
to 8.3, mainly because of the large amounts of
bicarbonate received from hydrothermal runoff.
Much of the water in Yellowstone’s hydrothermal
features begins as rain or snow. Precipitation
seeps into the ground and then rises back up as
it flows through the plumbing system of the feature—a
round trip which may take hundreds, or even thousands,
of years. In the case of a geyser, the water encounters
volcanic rocks underlying the geyser basin, and
becomes superheated. An eruption is triggered
when this water fills the geyser’s plumbing
system and the geyser begins to act like a pressure
cooker. Within a geyser’s plumbing system,
much of the water can reach temperatures greater
than 400°F (205°C) and still remain in
a liquid state due to the great pressure exerted
by overlying surface water and rock.
As more hot water continues to enter the geyser’s
plumbing at depth, the water temperature climbs
high enough to overcome the pressure. Some of
the water converts to steam. As the steam bubbles
become larger and more plentiful, they can no
longer rise freely past constrictions or narrow
places in the geyser’s plumbing system.
Temperatures build and the boiling becomes more
turbulent. Eventually the violent bubbling forces
some water through the constriction. This release
creates an instant reduction in pressure. Much
of the water in the system flashes instantly into
steam and forcibly ejects the remaining water.
The hydrothermal water carries chemicals, elements,
minerals, and bits of dissolved rock which drop
out of solution to coat the surrounding landscape
or to be carried into streams, such as the Firehole
River, by the thermal runoff.
The instructor will:
- Refrigerate at least one quart of water the
evening before the lesson.
- Heat water to boiling using an electric teapot,
hot plate, or prepare earlier and store in a
- Review the course of the Firehole River with
students, using Attachment A or another map
of Yellowstone National Park.
- Hand out copies of Attachment B to students.
- Instruct students to fill out Attachment B
during the course of this lesson.
- Remind students that the Firehole River passes
through 3 major geyser basins in Yellowstone
- Review the workings of a geyser with students,
as discussed in the Background section.
- Demonstrate an eruption using a film canister.
a. Punch a hole
into the lid of the canister with a ball point
pen and tell students that the hole represents
the constriction or narrow place in the geyser’s
b. Fill the
canister almost (more than ¾ full) to the
top with room temperature water.
c. Drop 1/2
of an antacid tablet into the water and seal with
the punctured lid.
d. Cover the
puncture with thumb and shake once, then uncover.
- When the “geyser” erupts, ask
students to observe where the water lands and
to extrapolate where the water might spread
when expelled from a real thermal feature in
- Ask students how the Firehole River might
be affected by thermal infusions.
- Write the formulas for converting temperatures
from Fahrenheit to Celsius, and vice versa,
on a blackboard and review with students.
- Select a student to measure ¾ cup cold
water and pour it into the heat- tolerant glass
- Select a student to take a temperature reading
of the cold water and announce the result to
- Instruct students to convert the water’s
temperature from degrees Fahrenheit to degrees
Celsius on their worksheets.
- Remind students that by the end of its run
through the geyser basins, nearly a quarter
of the water in the Firehole River comes from
the runoff of geysers and hot springs
- Select a student to measure ¼ cup hot
water and pour it into the cold water in the
heat-tolerant glass container.
- Select a student to take another temperature
reading of the water and announce the result
to the class.
- Instruct students to convert the water’s
temperature from Celsius to Fahrenheit on their
- Remind students that thermal water also contains
chemicals, minerals, and elements from its passage
through an underground plumbing system. When
thermal runoff enters a stream, the pH and water
chemistry of the stream may change, depending
on the character of the thermal features that
supply water. In the case of the Firehole River,
added bicarbonates make the river’s water
more alkaline (basic), though other thermally
influenced streams in Yellowstone become more
- Select a student to use litmus paper to take
a pH reading of the water and announce the result
to the class.
- Select a student to add ¼ cup baking
soda (an alkaline substance) into the water
and stir with spoon until it is thoroughly mixed.*
- Select a student to take another pH reading
and announce the result to the class.
* The instructor may want to repeat the experiment
using an acidic substance such as vinegar or
lemon juice for comparison.
in the Classroom Rubric (32KB pdf)