The Sahara Desert

 

Subject: Geology and Measurement

Topic: Students will consider the desertification process by studying the history of the Sahara Desert.

NSTA Teaching Standards: A, B, C, D, E, F

NSTA Content Standards:

            Unifying Concepts and Processes:

                        K-12: Change, constancy and measurement

            Science as Inquiry

                        K-12: Abilities necessary to do scientific inquiry

            Earth and Space Science

                        K-4: Changes in earth and sky

                        5-8: Earth's history

            Physical Science

                        9-12: Motions and forces

            History and Nature of Science

                        9-12: Historical perspectives

NCTM Standards

            Content Standard: Measurement

            Process Standards: Connections and Problem Solving

Teaching Procedures:

            Essential Questions:

                        What processes formed the Sahara Desert? How long has this been happening? Is it possible to predict the future of the Sahara Desert?

            Introduction (Activating):

Teaching Strategies:

 

 

            Closure:

 

            Differentiated Instruction:

1. Multiple intelligences addressed:

 

            Lesson Assessment:

 

 

            Materials/Resources

1. The Sahara Desert, Handout #1
2. Sahara Expansion, Handout #2
3. Desertification, Handout #3
4. Compute to Find Out, Handout #4
5. Discussion Guide, Handout #5
6. Essay Scoring Rubric (optional)

 

 

 

 

 

 

 

 

 

 

The Sahara Desert                                                                 Handout #1

  

Photo courtesy of http://www.photos-of-the-year.com/sahara-desert/

 

The Sahara Desert is the world's largest desert. It is growing at an incredible rate!

As the desert expands, it depletes natural resources needed for farming and feeding the people of Africa.

 

 

 

What causes the desert to expand?

 

 

 

 

 

How long has the Sahara desert been expanding?  

 

 

 

 

How will desertification affect the people of Africa?

 

Sahara Expansion                                                                 Handout #2

HBJ Earth Science, 1989, p. 277

 

What causes the desert to expand?

 

As the wind blows from East to West across the African continent, the desert expands. The picture above shows the past, present, and future size of the Sahara Desert, back in 1989.

 

 

 

 

 

 

 

 

 

 

 

 

 

Desertification                                                               Handout #3

Picture courtesy of: http://www.photos-of-the-year.com/sahara-desert/

 

What causes the desert to expand?

 

            "Parts of it look like the surface of Mars. Beginning in 1968, the Sahel—a vast, ancient savanna that borders the lush, tropical regions of West Africa—fell victim to a catastrophic five-year drought. Abnormally dry conditions sped up the invasion of a neighbor to the north: the Sahara, the world’s largest desert. When the grass- and shrubland of the Sahel lost its already limited ability to support crops and livestock, famine came to visit along with the sand.

            Verdant land can become desert as a result of drought, increased erosion due to land-clearing, poor farming techniques, overgrazing of livestock, and drainage of surface and underground water for crop irrigation and household and industrial use…

            …Perhaps the most frightening aspect of desertification is that it tends to be what scientists call a runaway phenomenon. Once it begins in a particular area, it is almost impossible to stop, and it cannot be reversed within a human lifetime."

Information quoted from http://www.nationalgeographic.com/eye/deforestation/phenomena.html

 

 

 

Sahara Desert                                                                                      Handout #4

What Happened to Those Cities?

 

In the times of the Roman Empire, approximately 2000 years ago, Northern Africa served as the breadbasket with 600 cities. These cities are now deserts. http://www.un.org/ecosocdev/geninfo/sustdev/desert.htm

 

The Sahara desert covers approximately 3,300,000 square miles of Africa. The United States, including Alaska and Hawaii, is approximately 3,700,000 square miles in comparison. http://exploringafrica.matrix.msu.edu/curriculum/lm16/actone.htm

 

The total area of the continent of Africa is approximately 11,700,000 square miles.

http://www.bu.edu/africa/outreach/materials/handouts/howbig.html

 

 

 

 

 

 

How many of the countries in Africa have been or will be affected by desertification?

 

 

The Future of Africa                                                             Handout #5

Compute to Find Out

 

http://www.map-of-africa.us/relief-map.htm

 

Facts:

Scientists estimate that the Sahara Desert began to form approximately 4000-6000 years ago. Scientists theorize that a slight change in the tilt of the earth’s axis caused climate changes associated with desertification. http://www.environmentalphilosophy.org/upcoming/uncharted_waters.pdf

 

The hot wind of the Sahara Desert cooks the edge of the desert and slowly destroys most of the vegetation. This process is currently happening at a rate of .325 miles per year. The size of the Sahara is constantly changing. Satellite imagery has shown that the desert boundary can move up to 200 kilometers (124 miles) per year when a dry year follows a wet year. http://www.unccd.int/publicinfo/factsheets/showFS.php?number=2

 

The Sahara Desert is approximately 1300 miles from the northern point to the southern point.

 

The Sahara desert covers approximately 3,300,000 square miles of Africa.

 

The total area of the continent of Africa is approximately 11,700,000 square miles.

 

Using the information above, if nothing is done to reverse the desertification, how long do you think it will take the Sahara to cover the African continent?

 

  

Handout #6

 

The Sahara Desert Discussion Guide                                                                  

 

 

1. What are the factors that contribute to the expansion (desertification) of the Sahara Desert?
2. In what ways was the continent of Africa different before the expansion of the desert?
3. At the current rate, how long will it take before the Sahara desert engulfs the entire continent of Africa?
4. What are some possible implications of desert expansion?
5. What are some possible solutions to the problem of desertification in Africa?
6. What do you know about earth's history from the study of the Sahara desert?
7. How accurate do you think your answer is?

 

  

Sahara Desert Activity

Essay Scoring Rubric

 

Name________________________                                                   Date_________________

 

Explain the process by which the Sahara Desert is expanding. What factors have contributed to its expansion? Do you think the Sahara Desert will expand to cover the entire continent of Africa? Based on the timeline of desertification that has taken place in the past, use scientific and mathematical thinking to figure out how long it will take the Sahara Desert to take over the entire continent of Africa. How accurate is your prediction? Explain your reasoning.

 

	Not Evident (0)	Needs Work (15)	Acceptable (20)	Exemplary (25)
Mathematical Thinking	There is no evidence of mathematical thinking.	The mathematical thinking is not expressed clearly or is expressed erroneously.	The mathematical thinking is correct.	The mathematical thinking is expressed correctly and in detail.
Calculations	No calculations are present.	The calculations are incorrect.	The calculations are correct.	The calculations are accurate and detailed.
Scientific Reasoning	No scientific reasoning is present.	The scientific reasoning present is incorrect.	Scientific reasoning is correct.	Scientific reasoning is correct and detailed.
Written Expression	The essay is not related to the topic or the essay is incoherent.	The writing is minimally coherent and/or has many grammar, punctuation, or spelling errors.	The writing is coherent, clear and understandable with few grammar, punctuation or spelling errors.	The writing is very coherent, expressive, persuasive, and clear with no errors.
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