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DRAFT
What's Under There?
Overview
In this activity students determine ways to make "observations" about
unknowns, such as the land beneath an ice sheet or the interior of the
Earth, using tools other than sight. In groups, the students build "mystery boxes"
and exchange them with other groups. Each group is permitted a limited
number of probes (cores) into the box; they must define a sampling strategy to
maximize the amount of information acquired. These conditions simulate restricted resources
available to research teams tackling similar challenges. The students
"map" their results and describe the interior of the box based on their
measurements. This activity leads into a subsequent activity that examines
remote sensing of the base of ice sheets.
Rationale
What is under the ice sheet? What is under the ocean? What is inside the
Earth? How do we know? We have been exploring our Earth for thousands of
years and we have many tools with which we can explore. Believe it or not,
we still do not know what every square centimeter looks like! Satellites
have helped us get a view of the surface, but what about the ocean floor and the land under the huge ice sheets of Greenland and
Antarctica? Most of this area remains mostly unknown! Scientists are finding out more and
more, however, as technology develops. They "image" these hard-to-get-to
locations remotely. That is, they use instruments that allow them to get a
picture or a sample without the scientist having to go under the ice or
into the deep ocean trenches.
Grade Level/Discipline
Middle School, Earth Science, Environmental Science
Objectives
The student will become acquainted with the concept that much of our
knowledge about the Earth is not derived from first-hand observations.
Much of our knowledge is extrapolated from isolated samples and sparse data.
The students will:
plan a sampling strategy to maximize information acquisition under sampling restrictions
organize the sample data
map the sample data
develop hypotheses about the remotely sampled region
National Standards
Teacher Preparation for
Activity
Place the objects in the aquarium or deep pan. Cover with water. Add a few
drops of India Ink to the water such that the students cannot see the objects in the container.
Materials
For the class:
aquarium or other deep container
solid objects (rocks, nuts and bolts, clay pots, water balloons, and
other non-floating objects)
ink
water
For each group of 4 to 5 students:
a shoe box with lid
masking tape
clay
straws or probes
ruler
graph paper that will fit over the box top
colored pencils
Time Frame
Two class periods
Teaching Sequence
Engagement and Exploration (Student Inquiry Activity)
Take the students to the prepared aquarium. Tell them that you have
submerged several objects under the water. Ask
the students to describe the objects without getting their hands wet or
removing any of the water. What can the students do to
figure out what is in the aquarium? What tools would they like to
use?
As a class, examine the large map of Antarctica
1. What's on the top of the continent?
2. What is under the ice?
3. What is under the water?
4. How do you know?
5. How might we find out?
Explanation (Discussing)
Researchers have been trying to figure out what is under the ice sheets of
Greenland and Antarctica for many decades. How thick is the ice? Are
there valuable minerals under the ice? Is the ice floating? Is the ice
getting thicker or thinner? Just like the students cannot put their hands
in the aquarium or drain the water off, the polar researchers cannot melt the ice to find out!
What do the students think the researchers do to figure out what is under
the ice? The students may suggest that the researchers dig holes to see
what is under the ice. This is one way! The research teams drill through
the ice to acquire ice cores (for other purposes); they also get other
valuable information such as the thickness of the ice and a sample of what
is under the ice sheet. However, the ice cores are expensive. Scientists
have other tools that they use. These will be explored in another activity.
Elaboration (Polar Applications)
Provide each group of students with a shoe box, top, and clay. Tell
each group that they will use their clay to construct a landscape in
their box. The landscape can look however they wish - it can have oceans
and mountains and arches.
After the student groups have prepared their boxes, have them put the top
on the box and secure it with tape. Ask the student groups exchange boxes. It might be a good idea to
exchange with groups that worked far apart, so that they will not have seen
the landscape.
Tell the groups that they will now describe the SURFACE of the landscape without peeking!
How might they go about this? The students may suggest that they stick
probes into the box to measure what is there. This is one way -- coring --
scientists find out what lies beneath the ice sheets. Coring or drilling
through the Earth or an ice sheet or to the ocean bottom is expensive,
however. This means that scientists cannot make as many holes as they
would like. They must carefully plan a sampling strategy. The students
will have to plan a sampling strategy, too. They will have 15 straws to
start with to sample the box.
Provide each group with 15 straws or probes, a ruler, graph paper, and colored
pencils. Have the groups draw a rectangle on the paper the same size as
the shoe box. Ask the students to put a small dot in the locations they
would like a sample. They will need to discuss the sampling strategy in
the group. What strategy will provide good coverage? What is the smallest
and largest feature they may sample with a parcticular strategy? Once a
sample plan is determined, the teacher can then poke holes in the box top at
that location, using a sharp skewer or a pair of scissors. Make sure the hole is
large enough to allow the straw probe fit through, but not large enough
for the students to see what is inside.
Ask the students to measure the height of the box in centimeters. Next, have the students mark the straws in centimeter increments from the bottom of the straw to the same height as the box height. This way, when the students measure the "topography" in the box, they need only read the number of centimeters remaining above the box top.
Push a straw into the box top. Mark the position on the corresponding point
on the paper. Continue to push the straw in, gently, until the straw just
touches the "land" in the box. Read the height of the straw above the box top, The students may have to estimate to the nearest centimeter. Measure the rest of the holes. If the students wish, they can leave the straws in the box - they will be able to "see" the topography reflected in the straw height.
When the holes have all been measured, ask the student groups to examine
their data. What trends do they see? Are there parcticular areas that would
benefit from additional coring? Are there areas that have large changes
but few cores? Are there "holes" in the dataset? Have each group present their findings to
the teacher and indicate where else that they would like to core and why.
At this point, the teacher can decide to "fund" additional sampling. Each
group can be granted up to 5 more straws to augment their sampled data.
After the additional cores have been collected and the positions and depths
recorded on the grid, the students are ready to make a contour map. Have the student groups examine their data. Are there areas of high numbers? Low numbers? What do these areas mean about the "land" inside the box? Where is it high? Low?
As the facilitator, work with the student groups to contour the data. Group the points on the paper that have the same or very close measurements, for instance, include all numbers from 0 to 0.5 centimeters above the box bottom; the next contour can include all numbers from 0.5 to 1.0 centimeters, etc.. Help the students determine which numbers to "lump." Use
different colors to group different levels of measurements. Do not cross over
any of the lines in any color.
Have the students finish their maps. What else should they include on their maps? What commonly occurs on maps? The students may want to indicate scale, contour interval, etc.
Exchange (Students Draw Conclusions)
When the groups have finished contouring their data, ask them to examine what they see. Have each group present their findings to the class. After each group has described the "land," permit the students to open the box to compare their results. Remind the students that scientists do not have the option to "open the box" or melt the ice sheet, or drain the ocean - enjoy it while they can!
Do the results of the contour map agree with the original? Why or why not? Where were more cores needed? Where might a few cores have sufficed? Where might cores not have provided information about depth and configuration of the topography (arches). If the students could do it over, with their knowledge of the land, how might they have placed the cores?
Where might scientists use similar methods for exploration? The students may name coring through ice sheets, finding depth in the ocean, and other exploration. What are the drawbacks to coring? Coring, or probing, can be expensive and the results are only for a single point. These results are extrapolated to other areas. Explorers can miss information.
In the next activity, students will explore other methods used by scientists to explore places they cannot visit in person.
Evaluation (Assessing Student Performance)
Authors
Sandra Shutey, Butte High School, Butte, Montana, with ideas from the
GLACIER curriculum design team.
Background
Resources
Satellite Image Map of Antarctica:
United States Geological Survey Information Services
Box 25286
Denver, CO 80225
1-800-HELP-MAP
(<$10.00)
Arctic Perspectives - Arctic Maps
Post Office Box 75503
St. Paul, Minnesota 55175
(612) 292-8599
Student Reproducible Masters
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look forward to hearing from you! Please review this activity.
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