PARALLELS AND SHADOWS

CAROL SCHOENBERGER

Grade Level: 7-12

Time: 2 periods

Theme

Location, Place

Purpose

To enable students to use higher level thinking skills in order to interpret, analyze and create descriptions of different places on earth so that their latitudinal location can be determined.

Objectives

Materials

Procedures

  1. As review, demonstrate why direct rays of the sun are hotter than indirect rays. Create a ray of sun by shining a flashlight on a globe through a 3/4" hole cut in an index card. Hold the card about two inches from the globe and aim the direct ray so that it falls on the latitude farthest toward the sun. (Tropic of Cancer or Equator is seen best). The students will observe how the ray is concentrated brightly in a small area. Then, keeping the card and flashlight horizontal, move the ray northward toward the pole. The students will see that the heat ray spreads out over a larger area as the earth's surface curves. Consequently, the area receiving the indirect rays is cooler. (It is necessary to conduct this demonstration in different parts of the classroom for those students whose view is blocked by the card or the back side of the globe.)
  2. Review the changing seasons by having a student stand at the front representing the sun while another student revolves around him/her carrying either a globe or a styrofoam ball marked with important parallels and having a dowel as the axis. The student who is orbiting the sun must be careful to hold the earth at a 23 1/2 degree tilt and to keep the poles pointing in the same direction. As the seasons change, ask questions of the class such as these:

If you have a sufficient number of globes, the class can be divided into small groups so that all students can have a turn in this exercise. Substitute globes can be made from paper plates and straws. On the back of the plates draw and label the Equator, both Tropics and Circles. Tape a straw on the front of one plate for the axis and then tape two plates together, back sides out. The drawback to these "globes" is that they are flat and some students have difficulty envisioning the sun's rays falling on the equator. The advantage is that they are inexpensive and made of handy materials.

  1. Pass out Activity Worksheet #1 Parallels and Shadows

a.       Have the students read the Problem and Observations.

b.      Direct the students to answer in writing questions 1-3, working individually.

c.       Place students in groups of four to discuss their choices and reasons (which should lead to the selection of the Tropic of Capricorn) and to write answers to #4.

d.      Have each group select a reporter to share the group's findings with the class.

                        Pass out Activity Worksheet #2

 .        Assign the students to create their own place descriptions. This can be done by individuals for homework or in groups as a class exercise.

a.       Have the students present their place descriptions to the class for solutions. This can be done in several ways:

1.      Selected students could write them on the board

2.      Selected students could read theirs while the class members write down key terms

3.      Groups could exchange their place descriptions

                        Conclude the lesson with a class discussion of the thinking strategies that they used to decide on locations.

Evaluation

  1. Observe students as they work in class.
  2. Collect Activity Worksheet #2 for grading.
  3. On the unit test or exam, give students passages to analyze, using a multiple choice format. The following questions are samples:

Your exploration team keeps getting lost in its world-wide journeys as it travels along the 50 degree east line of longitude. Use the following descriptions to determine your correct latitudinal location.

    1. ____ "It is midnight by my watch, which shows the date to be Dec. 15th, and yet I can write these notes by natural light, for the sun remains above the horizon."
      1. Equator
      2. Tropic of Cancer
      3. Arctic Circle
      4. Antarctic Circle
    2. ____ "There are stretches of barren sand and rock formations as far as we can see in all directions. Even though we shivered through the night, we feel as if we will perish from the heat during the day. My journal tells me that it is the 12th of March, and as we trudge northward at noon our shadows extend before us."
      1. Antarctic Circle
      2. Tropic of Cancer
      3. Tropic of Capricorn
      4. Equator
    3. ____ "We have been adrift in our life raft for a day now, and the heat would do us in except for the heavy rainfall. We drifted past an island covered with lush green vegetation but could not reach shore. It is Sept. 23rd, and as the sun sets in the west, we notice that our shadows stretch out directly eastward."
      1. Tropic of Cancer
      2. Equator
      3. Tropic of Capricorn
      4. Arctic Circle

ACTIVITIES WORKSHEET #1 - PARALLELS AND SHADOWS

The Problem

You are one member of a four-person exploration team that has been lost in the wilderness for several days. You know that your longitude is approximately 60 degrees west and that it is January the tenth. You have radio contact with the outside world. Your team must determine its approximate latitudinal location and radio this information out to direct search efforts. You decide to take careful note of your surroundings and to use your knowledge of physical geography to help your group determine its latitude.

Observations

"It was nearly 9:00 p.m. before darkness overtook our camp and we folded up our maps for the evening. It was quite warm, so we did not build a fire to cook our evening meal. By 5:30 the next morning it was light enough for Joe and me to head out to the east through the dry grasslands and scattered trees in search of drinking water. Just before noon we came upon a small stream running south through a marshy area. As we headed back west toward camp with our drinking water, Joe remarked that our shadows, off to our left, were very short - almost beneath us. This seemed a bit strange to us, but we dismissed it with no further thought. It was very hot now. We longed for a chance to rest under one of the occasional trees that we saw, but decided that it was best to press on. When we got back to camp, we made a list of the things we knew about this place in an effort to determine our approximate latitude."

Solution

  1. At which of the following parallels do you conclude that you are located?
    1. Tropic of Cancer
    2. Antarctic Circle
    3. Equator
    4. Tropic of Capricorn
    5. Arctic Circle

Answer: _________________________

  1. Why do you think the exploration team is located at the parallel you chose? Mention as many clues as you can.
  2. How do the shadows which you observed help identify your location?
  3. Name at least one of the four parallels that you did not select (see #1) and explain why it could not be the correct location of the exploration team.

ACTIVITIES WORKSHEET #2 - PARALLELS AND SHADOWS

CREATE YOUR OWN SCENARIO

Choose one of the parallels from the following list and write a place description that contains clues, similar to the previous one, that can be used by classmates to determine the parallel you have selected.

A.    Tropic of Cancer

B.     Antarctic Circle

C.     Equator

D.    Tropic of Capricorn

E.     Arctic Circle

F.      45 degrees north latitude

G.    45 degrees south latitude

The Problem

It has been some time since your exploration team was rescued. You are now on another journey and, sure enough, you are lost again! You know that the date is _____________________ and that your longitude is approximately ____________________________. You have observed the place carefully and made the following notes:

Observations

 

 

Solution

You are located ___________________________________________.