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 Fall of the Leaning Tower Classroom Activity

Objective
To experiment with different soil structures and the ability of each to carry a specific load.

• copy of "Hold It Up" student handout (HTML)
• bucket each of dirt, sand, and gravel
• clear container big enough to hold a brick
• brick
• ruler with centimeter scale
• coffee can or coring device
1. Begin by discussing the nature of soil. (See Activity Answer for background information.)

2. Following the discussion, take a core sample of soil from the schoolyard or other area. Study the sample and have students describe the soil's content layers.

3. Organize students into groups and distribute a copy of the "Hold it Up" student handout. The activity's goal is to mix the soil sample that will best support a brick on end.

4. As a class, have students decide what the experiment's parameters will be, such as whether to define a depth for the soil sample, whether all soil types must be used, and whether the materials list should be expanded to include additional soil types or other items.

5. Have students record and illustrate their sample makeup in journals.

6. Once all groups have finished, have each group stand the brick upright in the center of its soil sample. Let the bricks stand overnight. The next day, have students measure the indentations left by the bricks.

7. As a class, discuss the depth of each groups' brick indentation. Then have students try another mix, repeat the experiment, and measure again. Discuss the new results, comparing similarities and differences to the original soil samples.

8. As an extension, have students lay the brick on its side in the same soil mixture they used to lay the brick on end, or have students test the brick both ways after saturating the mixture with water. Are the indentations the same? If not, what accounts for the differences?

Students' results will vary. Compare the soil makeup of the group whose brick left the least indentation to those of the other groups. In which ways are they alike? How do they differ? What might students infer from this?

Soil is made up of inorganic and organic particles. Inorganic particles include rocks and minerals, such as clay, silt, sand, gravel, and stone. Organic particles may include decomposed plants and animals and living plant roots.

The structure of soil is determined by the arrangement of particles, which account for the pore space within the soil that may be filled with air or water. The nature of soil is determined by the parent rock from which it came, the climate that has weathered it, the vegetation it contains, the topography where it lies, and the time it has had to mature. The U.S. Department of Agriculture, which maps and collects soil data, has cataloged more than 50,000 different varieties of soil in the United States.

Civil engineers specializing in soil mechanics determine whether a soil substrate is suitable to build upon, and if not, what measures need to be taken to make it safe. Civil engineers work with structures such as buildings, highways, dams, and bridges.

Article

Heiniger, Paolo. "The Leaning Tower of Pisa." Scientific American (December 1995): 62-67.
Describes how the tower has been leaning since first built, specifies the layers of soil beneath the monument, and discusses how modern technology is being used to keep the tower standing. The author is a member of the committee working to save the tower.

Web Sites

NOVA Online - Fall of the Leaning Tower
http://www.pbs.org/nova/pisa/
Includes a 360-degree QuickTime panorama of Pisa's famed Field of Miracles, an update on the recent soil-extraction method that slightly restored the tower's position, a look at the restoration of other monuments worldwide, and an interactive game that recreates some of the experiments Galileo conducted while in Pisa.

The Leaning Tower of Pisa
http://www.endex.com/gf/buildings/ltpisa/ltpisa.html
Includes facts and figures about the tower, its history, architecture, construction details, and proposals to save the tower. This site also has press listings for current news events.

ltpwww.gsfc.nasa.gov/globe/index.htm
Contains information about how much soil there is on Earth, what soil looks like, what soil does, how soil has played a role in criminal cases, and a listing of ideas for science fair projects. This site accepts questions about soil at: globe@ltpmail.gsfc.nasa.gov.

United States Geological Survey: Learning Web
http://www.usgs.gov/education/
Provides background information on geologic hazards and mapping. This site also links to Ask-a-Geologist where students can send earth science questions to USGS scientists.

The "Hold It Up" activity aligns with the following National Science Education Standards:

 Science Standard A:Science as Inquiry

Abilities necessary to do scientific inquiry

• Design and conduct a scientific investigation.

• Use appropriate tools and techniques to gather, analyze and interpret data.

• Develop descriptions, explanations, predictions, and models using evidence.

• Think critically and logically to make the relationships between evidence and explanations.

• Recognize and analyze alternative explanations and predictions.

• Communicate scientific procedures and explanations.

 Science Standard D:Earth and Space Science

Structure of the earth system

• Soil consists of weathered rocks and decomposed organic material from dead plants, animals, and bacteria. Soils are often found in layers, with each having a different chemical composition and character.

 Science Standard A:Science as Inquiry

Abilities necessary to do scientific inquiry

• Design and conduct a scientific investigation.

• Formulate and revise scientific explanations and models using logic and evidence.

• Develop descriptions, explanations, predictions, and models using evidence.

• Recognize and analyze alternative explanations and predictions.

• Communicate and defend a scientific argument.

 Fall of the Leaning Tower Original broadcast:October 5, 1999