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A Geological Puzzle (Grades 7-8)

MASTER TEACHER

Helen Schiller

OVERVIEW

In this lesson, students will make comparisons between continents, including rock ages and rock types to determine if continents had been joined at one time.

ITV SERIES

The Earth Revealed, Lesson 5: The Birth of a Theory

LEARNING OBJECTIVES

Students will be able to:

determine the age of a rock section by using a radioactive decay curve
estimate the unknown ages of rock sections using inference
show how two imaginary continents could have been combined using rock age and type

SC MATH/SCIENCE STANDARDS MET Science-Middle School

Process Skills

Observe
Observe patterns of objects and events

Measure
Use metric units

Infer

Make inferences based on data (measurements and observations)
Discriminate among observations, inferences, and predictions

Communicate

Communicate findings of investigations to others
Interpret and describe patterns of data on graphs, maps, diagrams, and charts

Mathematics - Middle School

Number and Numeration Systems
Understand and use real numbers in a variety of equivalent forms in a variety of real-world and mathematical problem situations

Numerical and Algebraic Concepts and Operations

Represent situations and number patterns with models, tables, graphs, verbal rules, and equations and make connections among these representations
Analyze tables and graphs to identify properties and relationships

Probability and Statistics

Collect, organize, analyze, describe, and make predictions with data
Construct, read, and interpret tables, graphs,
charts, and other forms of displayed data

MATERIALS

(per group of 3 or 4)

one envelope: puzzle pieces (puzzle template and answers that make up the first activity, found on pages marked Activity Sheet 1)
Activity Sheets 2
construction paper
glue
scissors

PRE-VIEWING ACTIVITY

NOTE: Teacher preparation for this activity follows.

Students complete the Puzzle Activity found on Activity Sheet 1 in teams of 3-4. Each team is to complete their puzzle by silently giving pieces to other groups: they may not beg, point, or take pieces from other groups. Each group must obtain all pieces necessary to complete the puzzle, and have no pieces left over - - extras must be given away to other groups. This is a cooperative/ competitive activity)~ and each class can be timed to see which class can complete all puzzles in the least amount of time. (It's fun to make a contest of this and tell the teams that as they finish, they are to write a brief explanation of how this activity ties in with plate tectonics.)

When the teams have completed their puzzles, tell the students that the pieces are in the shape of the actual lithospheric plates of the earth. Show the transparency of the plates and discuss the direction of plate movement, using terms for plate boundaries as shown in the vocabulary section. Discuss Alfred Wegener (meteorologist, early 1900's) and his theory of continental drift. Have students hypothesize about how this movement would affect landforms, earthquakes, volcanoes, etc. Lead students to the next activity by asking them to infer how scientists could determine the age or type of rock found on coastlines from this understanding of plate movement.

Teacher Preparation for Puzzle Activity

1. Prepare a puzzle sheet for each group. Glue the puzzles on different colored construction paper, laminate, and cut out the pieces. (Ex: 6 groups, 6 colors)

2. Mix up the pieces so that each group gets pieces from each color. Be sure that each group gets at least one large piece and a couple of small pieces from one color. Put the mixed up pieces in envelopes, one envelope per group.

3. Be sure that after students complete the puzzle and after class discussion, that they mix up the pieces for the next classes. They'll enjoy that!

VOCABULARY

plate tectonics
lithospheric plates
diverging plate boundary
continental drift
converging plate boundary
radioactive decay curve
transform plate boundary

FOCUS FOR VIEWING

To give students a specific responsibility while viewing The Earth Revealed, The Birth of a Theory, have students listen for the explanation of plate tectonics. They will view simulations ofplate movement along with actual footage and will listen for the ways that scientists use rock ages and type to determine plate movement.

VIEWING ACTIVITIES

Start The Birth of a Theory tape just after scientist Jason Saleeby initially speaks (approximately 4 minutes into the tape). There will be a map of South America and Africa. Have students listen for evidence of former match-up. Audio cue: "When he fit Africa against South America, Wegener discovered...." Pause at, "... with those in South America." Time: approximately 26 seconds. Answer: Mineral match-up, mountain range similarities, and the ages of ancient rocks matched.

Tell students that these pieces of evidence were very solid evidence for Wegener's theory of continental drift. Wegener could not, however, explain how the massive continents could "drift," and as a result, many scientists of his time did not accept his theory.

Discuss with students that later in this century (1940's), other scientists during World War 11 used technology created for the war effort to gather more information about the mechanism that moved the giant continents. By the 1960's, a scientist by the name of Harry Hess was important in this discovery.

Say, "Listen for Hess's theory and the way it explained the separating continents." Start the tape after the diagram of seafloor guyots. Audio cue: "Harry Hess had a bold, imaginative concept..." and end at "... from one another," with the scientist talking in the library. Time: approximately one minute. Answer: At the mid-Atlantic ridge, the crust is separating and pushing apart, creating new crust.

Discuss the fact that this theory would account for an enlarging crust of the earth, but in fact, the crust is not enlarging. Hess came up with a theory to explain that as well. Say, "Listen to find out how Hess provided answers for this anomaly." Start the tape about 13 minutes into the tape at the picture of a crevasse in the ocean floor at the audio cue: "Hess suggested that the
ocean floor simply sinks back and pause the tape at "...so, too, was the model of sea-floor spreading." Time: approximately 22 seconds.

Answer: Hess's ideas explained how the continents could move because it placed them on moving "plates".
Ask, "What geologic formations or aspects of earth's history-could be explained by the theory of plate tectonics (the theories of continental drift and sea-floor spreading)?" Have students listen for the answer to the question. Start tape at picture of the seamounts; on the ocean floor (approximately 20 minutes into the tape) at the audio cue: "As transform faults were being discovered,..." and go approximately 1.5 minutes and pause after "...giant plates which slowly spread, converge, or slide by one another." Answer: fossils, paleoclimates, mountain ranges, mineral resources, and large faults.

Tell students that geologists have been trying to find out more about the movement of lithospheric plates, and that one factor that would be helpful would be to know the age of the rocks and the other would be a match of rock types. Students now complete the exercise found on the sheets labeled Activity Sheet 2.

NOTE: You will need to discuss radioactive elements (those that decay and allow scientists to measure that decay, giving the age of the surrounding material) with the students. They may also need an explanation of the graph of the radioactive decay curve. Students will also have to close the separation between the 2 rock sections that have formed a 'T" shape by folding their paper.This may not be evident to all students.

ACTION PLAN

Students can re-enact a debate that may have occurred among scientists of Wegener's time. They can research the beliefs of scientists of the period. After the debate, they can research on the Internet to get current information on explorations of the ocean floor to bolster Wegener's point of view. They can then display the information in a manner showing Pangaea and today's arrangement of continents.

EXTENSIONS

Writing: Students can work in teams and write a history of their supercontinent. They should include how the movement of the plates and the
-consequent change in landfonns would have affected the life forms of the area.

Mathematics: Have students create word problems for their supercontinent using the rate of movement determined in the conclusion of the activity.

Art: Students can create a creature that remained on one side of their supercontinent after the split. Remind them of species such as kangaroos and koalas that retained their unique characteristics because of isolation due to continental drift. They can sketch the creature or actually "build" one, but they should be able to show a special characteristic that the animal could have retained over time.

Social Studies: Have students make a map of South Carolina showing the geographical regions of the state and use the information on plate tectonics and the ancient collisions of the North American and African continents to explain how our state's regions developed.