Hydrothermal Vent Challenge

2004 Ring of Fire Expedition
Hydrothermal Vent Challenge
FOCUS
TEACHING TIME
Chemistry of hydrothermal vents
One 45-minute class period, plus time for Internet
research
GRADE LEVEL
9-12 (Chemistry)
SEATING ARRANGEMENT
Classroom style if students are working individually,
FOCUS QUESTION
or groups of two to four students
What are common features of hydrothermal vent
fluids, and how can these features be used to
MAXIMUM NUMBER OF STUDENTS
locate undiscovered hydrothermal vents?
30
LEARNING OBJECTIVES
KEY WORDS
Students will be able to define hydrothermal vents,
Ring of Fire
and explain the overall processes that lead to their
Asthenosphere
formation.
Lithosphere
Magma
Students will be able to explain the origin of min-
Fault
eral-rich fluids associated with hydrothermal vents.
Transform boundary
Convergent boundary
Students will be able to explain how “black smok-
Divergent boundary
ers” and “white smokers” are formed.
Subduction
Tectonic plate
Students will be able to hypothesize how proper-
Hydrothermal vent
ties of hydrothermal fluids might be used to locate
Chimney
undiscovered hydrothermal vents.
Black smoker
White smoker
MATERIALS
Hydrothermal plume
 Copies of “Hydrothermal Vent Challenge,” one
CTD
copy per student or student group
Tow-yo
Phase separation
AUDIO/VISUAL MATERIALS
None
BACKGROUND INFORMATION
The Ring of Fire is an arc of active volcanoes and
earthquake sites that partially encircles the Pacific
Ocean Basin. The location of the Ring of Fire coin-
1

2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
Focus: Chemistry of hydrothermal vents
oceanexplorer.noaa.gov
oceanexplorer.noaa.gov
Focus: Chemistry of hydrothermal vents
cides with the location of oceanic trenches and vol-
ary. These island arcs are always landward of the
canic island arcs that result from the motion of the
neighboring trenches.
large plates (tectonic plates) that make up the outer
shell of the Earth (the lithosphere). These plates
The 2004 Ring of Fire Expedition continues explo-
consist of a crust about 5 km thick, and the upper
ration of the convergent plate boundary that forms
60 - 75 km of the Earth’s mantle. The plates that
the Mariana Arc, part of the Ring of Fire that lies
make up the lithosphere move on a hot flowing
to the north of Guam in the western Pacific. Here,
mantle layer called the asthenosphere, which is
the fast-moving Pacific Plate converges against the
several hundred kilometers thick. Heat within the
slower-moving Philippine Plate. The Pacific Plate is
asthenosphere creates convection currents (similar
subducted beneath the Philippine Plate, creating the
to the currents that can be seen if food coloring is
Mariana Trench (which includes the Challenger
added to a heated container of water). These con-
Deep, the deepest known area of the Earth’s
vection currents cause the tectonic plates to move
oceans). The Mariana Islands are the result of vol-
several centimeters per year relative to each other.
canoes caused by this subduction, which frequently
causes earthquakes as well. The movement of the
Where tectonic plates slide horizontally past each
Pacific Ocean tectonic plate has been likened to a
other, the boundary between the plates is known
huge conveyor belt on which new crust is formed at
as a transform plate boundary. As the plates rub
the oceanic spreading ridges off the western coasts
against each other, huge stresses are set up that
of North and South America, and older crust is
can cause portions of the rock to break, resulting
recycled to the lower mantle at the convergent
in earthquakes. Places where these breaks occur
plate boundaries along the underwater volcanoes
are called faults. A well-known example of a trans-
and island arcs of the western Pacific. While many
form plate boundary is the San Andreas Fault in
volcanoes in the Mariana Arc have been mapped
California.
and sampled in recent years, the Ring of Fire
Expeditions are the first explorations focused spe-
Where tectonic plates are moving apart, they form
cifically on submarine hydrothermal systems of the
a divergent plate boundary. At divergent plate
Arc.
boundaries, magma (molten rock) rises from deep
within the Earth and erupts to form new crust on
Underwater volcanism at spreading ridges and
the lithosphere. Most divergent plate boundaries
convergent plate boundaries produces hot springs
are underwater (Iceland is an exception), and form
known as hydrothermal vents. Scientists first discov-
submarine mountain ranges called oceanic spread-
ered hydrothermal vents in 1977 while exploring
ing ridges.
an oceanic spreading ridge near the Galapagos
Islands in the submersible Alvin. In addition, the
A convergent plate boundary is formed when tec-
scientists also found that the hydrothermal vents
tonic plates collide more or less head-on. Usually
were surrounded by large numbers of animals that
one of the converging plates moves beneath the
had never been seen before. These biological com-
other (a process called subduction). Deep trenches
munities depend upon specific chemical processes
are often formed where tectonic plates are being
that result from the interaction of seawater and hot
subducted, and earthquakes are common. As the
magma associated with underwater volcanoes.
sinking plate moves deeper into the mantle, fluids
are released from the rock causing the overlying
In this lesson, students wil research some of these
mantle to partially melt. The new magma rises and
processes, their relationship to hydrothermal vent
may erupt violently to form volcanoes, often form-
communities, and how these processes provide a
ing arcs of islands along the convergent bound-
means for locating undiscovered hydrothermal vents.
2
3

2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
Focus: Chemistry of hydrothermal vents
oceanexplorer.noaa.gov
oceanexplorer.noaa.gov
Focus: Chemistry of hydrothermal vents
Refer to the 2002 Ring of Fire Expedition for lesson
stances increases with increasing temperature.
plans developed for Grades 9-12 (http://oceanexplorer
e.noaa.gov).
• Hot seawater in hydrothermal vents does not boil
because of the extreme pressure at the depths
LEARNING PROCEDURE
where the vents are formed.
1. Review the concepts of plate tectonics, being sure
that students understand the processes that take
• Chimneys are minerals deposited from hydrother-
place at convergent and divergent boundaries,
mal vent fluids when the fluids are cooled by sur-
and why these boundaries are often the site of
rounding seawater, thus lowering the solubility of
volcanic activity. Tell students that their assign-
many of the dissolved materials.
ment is to research some of the chemical interac-
tions that take place between seawater and the
• “Black smokers” are chimneys formed from depos-
volcanic magma.
its of iron sulfide, which is black.
2. Distribute copies of “Hydrothermal Vent
• “White smokers” are chimneys formed from
Challenge” to each student or student group. You
deposits of barium, calcium, and silicon, which
may want to direct students to the following web
are white.
sites:
http://www.ocean.udel.edu/deepsea/
• Hydrothermal plumes are formed by the chemi-
http://www.pmel.noaa.gov/vents/chemocean.html
cally-altered seawater that emerges from hydro-
http://www.pbs.org/wnet/savageearth/hellscrust/html/
thermal vents. Because the heat and chemical
sidebar2.html
composition of the plumes is distinctly different
http://www.geneseo.edu/~jc99/whatarethey.html
from the surrounding seawater, these properties
http://www.accessexcellence.com/BF/bf01/arp/
can be measured and indicate the presence of
hydrothermal vents. Some of these parameters
3. Lead a discussion of students’ research results.
(especially helium) can be detected as far as tens
The following points should emerge from this
to hundreds of kilometers away from the vents
discussion:
that produced them.
• Hydrothermal vents are the result of sea water
• A CTD is an instrument package that measures
percolating down through fissures in the ocean
conductivity, temperature, and depth. The pack-
crust in the vicinity of spreading centers or sub-
age usually includes additional instruments
duction zones. The cold seawater is heated by
to measure pH, transmissivity (a measure of
hot magma, and re-emerges to form the vents.
interference with light transmission through sea
water, which can indicate the presence of sus-
• As the seawater is heated, some chemicals (such
pended particles), and concentrations of certain
as magnesium and sulfate ions) are removed,
chemicals (such as iron and sulfur that are often
while many others (such as sulfur, copper, zinc,
enriched in vent plumes).
gold, iron, and helium) are transferred to the
water from the hot crust material.
• To search for hydrothermal plumes, scientists tow
a CTD behind a research vessel, and gradually
• Seawater in hydrothermal vents may reach tem-
raise and lower the instrument package as the
peratures of over 340°C (700°F). The extremely
ship moves along. The motion of the instrument
high temperatures contribute to the solution of
package is thus similar to a yo-yo, and this kind-
these materials, since the solubility of many sub-
of exploration is called a “tow-yo” operation.
2
3

2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
Focus: Chemistry of hydrothermal vents
oceanexplorer.noaa.gov
oceanexplorer.noaa.gov
Focus: Chemistry of hydrothermal vents
• Phase Separation is the separation of a substance
http://pubs.usgs.gov/publications/text/dynamic.html#anchor19309449
into two or more phases (vapor, liquid, or solid).
– On-line version of “This Dynamic Earth,” a
Under the high temperature and pressure condi-
thorough publication of the U.S. Geological
tions of hydrothermal vents, a vapor phase may
Survey on plate tectonics written for a non-
separate and move away from a higher-salinity
technical audience
liquid phase. Each phase contains a distinctly dif-
ferent combination of dissolved materials.
http://pubs.usgs.gov/pdf/planet.html – “This Dynamic Planet,”
map and explanatory text showing Earth’s
• The primary producers in hydrothermal vent
physiographic features, plate movements,
communities are a wide variety of bacteria and
and locations of volcanoes, earthquakes,
Archaea that utilize sulfur, hydrogen, methane
and impact craters
and other compounds released by the reactions
between seawater and magma.
http://volcano.und.nodak.edu/vw.html – Volcano World web
site
THE BRIDGE CONNECTION
www.vims.edu/bridge/ – Click on “Ocean Science
http://oceanexplorer.noaa.gov/explorations/03fire/logs/subduction_
Topics” then “Marine Geology.”
vr.html – 3-dimensional “subduction zone”
plate boundary video
THE “ME” CONNECTION
Have students write a brief essay describing why
http://oceanexplorer.noaa.gov/explorations/03fire/logs/ridge.html
processes at hydrothermal vent communities are (or
– 3-dimensional structure of a “mid-ocean
are not) relevant to their own lives.
ridge,” where two of the Earth’s tectonic
plates are spreading apart
CONNECTIONS TO OTHER SUBJECTS
English/Language Arts, Geography, Biology, Earth
NATIONAL SCIENCE EDUCATION STANDARDS
Science
Content Standard A: Science as Inquiry
• Abilities necessary to do scientific inquiry
EVALUATION
• Understandings about scientific inquiry
Written answers to the “Hydrothermal Vent
Challenge” collected prior to group discussion pro-
Content Standard B: Physical Science
vide a means of assessment.
• Chemical reactions
• Interactions of energy and matter
EXTENSIONS
Have students visit http://oceanexplorer.noaa.gov to keep
Content Standard C: Life Science
up to date with the latest Ring of Fire Expedition
• Interdependence of organisms
discoveries.
• Matter, energy, and organization in living sys-
tems
RESOURCES
http://oceanexplorer.noaa.gov – Follow the Ring of Fire
Content Standard D: Earth and Space Science
Expedition daily as documentaries and dis-
• Energy in the Earth system
coveries are posted each day for your class-
• Geochemical cycles
room use. A wealth of information can also
be found at both of these sites.
Content Standard E: Science and Technology
• Understandings about science and technology
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2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
oceanexplorer.noaa.gov
Focus: Chemistry of hydrothermal vents
Student Handout
Hydrothermal Vent Challenge
1. What are hydrothermal vents, and how are they formed?
2. How is the chemical composition of hydrothermal vent fluid different from surrounding
seawater?
3. What temperatures are typical of hydrothermal vent fluids? How does this affect the
chemical composition of the fluid?
4. Why doesn’t seawater boil in hydrothermal vents ?
5. What are vent chimneys, and how are they formed?
6. What are “black smokers,” and why are they black?

2004 Ring of Fire Expedition – Grades 9-12 (Chemistry)
oceanexplorer.noaa.gov
Focus: Chemistry of hydrothermal vents
7. What are “white smokers”
Student Handout
and why are they white?
8. What are hydrothermal plumes? How can they be used to locate undiscovered hydro-
thermal vents?
9. What is a CTD?
10. What is a “tow-yo” operation?
11. What is phase separation, and how does it affect the composition of hydrothermal
vent fluid?
12. What are the primary producers in hydrothermal vent communities, and what is their
source of energy?