Relative Dating Using "The Block"
Initial Publication Date: August 25, 2009
Summary
In this activity students will work to decide the sequence of events using their powers of observation. Pairs of students will be given a block of wood that hat been painted, nailed and gouged and instructed to deduce the order of events and to justify their answers.
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Learning Goals
Students will use observation skills to appraise, compare, analyze, and sequence the order in which certain events happened to a block of wood.
Context for Use
This lab activity is a great introduction to relative dating. It is ideal to have one block for every two students. The blocks need to be prepared ahead of time and will take you about 2 to 3 hours to make about 15. Instructions to make them are on page two. It should take about 20 minutes or so for students to do the activity and the amount of discussion time after depends on the teacher and the class. This activity is geared to 9th grade physical science students but could be modified to use with senior high earth science students as well.
Description and Teaching Materials
Introduction: When scientists need to determine the age of rocks there are two methods they use. One method is radiometric dating and the other is relative dating. With relative dating they can not determine the exact age of the rocks, but they can determine with some certainty which rocks are younger and which are older using something called the principle of superposition. The principle of super position basically says that unless rock layers have been disturbed the youngest ones are on the top and the oldest are on the bottom.
Procedure: Give each pair of students a prepared block. Tell them they need to determine what sequence each thing happened to the block and justify their answer. They need to write the sequence they propose on a sheet of paper with the justification next to each step. When all have finished have two groups join and discuss their answers.
Conclusion: Finally have all students join in a class discussion of their answers. Be certain to have them explain how they "know" what order things occurred in. There may be some things they can not determine the order for and that is fine. Point out scientists can only make hypothesis based on the evidence that is there and that we may not know for certain, because we were not there to witness what happened. I like to leave them wondering and not give them the actual sequence. Tell students to take two minutes to think about what they have learned then record their thoughts in their journal. This sequencing activity would also work to introduce the geologic time scale and the concept of index fossils.
Inquiry Blocks
This is a great inquiry activity for teaching sequencing. This idea was first shared with me at a MnSTEP work shop. I have since worked with it to make it my own.
This can be used to teach sequencing in rock layers. A teacher could increase the difficulty by making the blocks different and leaving some sequencing clues off different sets of blocks. After students have done the sequencing for their blocks, they could be paired with a group that has the complementary block to theirs and have both groups work to solve the sequencing riddle.
Materials:
lengths of 2X4 or 4X4 board, 5 different colors of paint (I used black, brown, grey, green and white), several nails, or screws, staples, wood filler
Procedure:
*Cut a wooden 2X4 or 4X4 into 4 inch long pieces.
*Scratch, paint, or nail on the board.
*Overlap paint, scratches, and nails so you are layering.
You can do this in any order you wish. This is just the order I used for my blocks.
1. Paint white on the bottom and about 1/4th the way up the block.
2. Pound a nail just above the white line.
3. Paint a brown ring, about an inch wide, just above the white overlapping the white slightly and overlapping the nail.
4. Cut a deep gash in the wood through the brown layer into the plain wood area.
5. Fill cut with colored wood filler.
6. Paint a black streak diagonally across the top of the block.
7. Screw a sheet rock screw into the top and into the black streak.
8. Paint a grey streak over the black but not over the screw.
9. Paint a white streak over the black and grey, not over the screw.
10. Paint a green dot in an unpainted corner of the block.
You can add more steps or skip some depending on your supplies and the degree of difficulty you want to achieve.
Procedure: Give each pair of students a prepared block. Tell them they need to determine what sequence each thing happened to the block and justify their answer. They need to write the sequence they propose on a sheet of paper with the justification next to each step. When all have finished have two groups join and discuss their answers.
Conclusion: Finally have all students join in a class discussion of their answers. Be certain to have them explain how they "know" what order things occurred in. There may be some things they can not determine the order for and that is fine. Point out scientists can only make hypothesis based on the evidence that is there and that we may not know for certain, because we were not there to witness what happened. I like to leave them wondering and not give them the actual sequence. Tell students to take two minutes to think about what they have learned then record their thoughts in their journal. This sequencing activity would also work to introduce the geologic time scale and the concept of index fossils.
Inquiry Blocks
This is a great inquiry activity for teaching sequencing. This idea was first shared with me at a MnSTEP work shop. I have since worked with it to make it my own.
This can be used to teach sequencing in rock layers. A teacher could increase the difficulty by making the blocks different and leaving some sequencing clues off different sets of blocks. After students have done the sequencing for their blocks, they could be paired with a group that has the complementary block to theirs and have both groups work to solve the sequencing riddle.
Materials:
lengths of 2X4 or 4X4 board, 5 different colors of paint (I used black, brown, grey, green and white), several nails, or screws, staples, wood filler
Procedure:
*Cut a wooden 2X4 or 4X4 into 4 inch long pieces.
*Scratch, paint, or nail on the board.
*Overlap paint, scratches, and nails so you are layering.
You can do this in any order you wish. This is just the order I used for my blocks.
1. Paint white on the bottom and about 1/4th the way up the block.
2. Pound a nail just above the white line.
3. Paint a brown ring, about an inch wide, just above the white overlapping the white slightly and overlapping the nail.
4. Cut a deep gash in the wood through the brown layer into the plain wood area.
5. Fill cut with colored wood filler.
6. Paint a black streak diagonally across the top of the block.
7. Screw a sheet rock screw into the top and into the black streak.
8. Paint a grey streak over the black but not over the screw.
9. Paint a white streak over the black and grey, not over the screw.
10. Paint a green dot in an unpainted corner of the block.
You can add more steps or skip some depending on your supplies and the degree of difficulty you want to achieve.
Teaching Notes and Tips
This activity is a great way to incorporate inquiry into the classroom. Once you have made the blocks and given them to students you become a guide and students do the work.
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Assessment
The student work will be their journal entries which will be reviewed for understanding by the teacher.
Standards
Physical science Earth Space Science:
Earth Structure and processes Standard 3 code:9.3.1.3.1
Earth Structure and processes Standard 3 code:9.3.1.3.1