Author: Tess Ewart
Source: Adapted from PALS - http://pals.sri.com/tasks/5-8/Creeping/
Show an image of a mountain range or a fault line. One that can be found at the following web sites:
Georgia Perimeter College: Mass Wasting
Earth Science World Image Bank
Ask the students: "How fast are the mountains moving? How fast are Earth's tectonic plates moving? (most can be measured in centimeters per year) How do you know? How do scientists know?" (accept all answers - scientists can use sensors to take detailed measurements)
Tell the students that, "Scientists have to keep accurate data over time. They usually represent this data in graphs to convey their ideas to other people. Why is it important for students to be able to read graphs effectively?" (Being able to read graphs effectively can improve students' scientific literacy) The best way to work on this skill is to have students construct graphs of their own.
Discuss with the students why it is important to have experiments repeated several times. (Repeating experiments several times ensures the validity of the results and conclusions)
Tell the students that "scientists also represent their ideas using models." Students will now use a model to represent a type of slow mass wasting called creep.
Assessment: Student discussion
- Set up the equipment exactly as it appears in the Picture. Specify 3 heights - determined by what is used to elevate the clipboard. Use the tape to hold the beaker in the correct location. ** The creeping material must flow down the metric scale on the ruler. **
- Turn the clipboard so the beaker is upright. Add creeping material to the beaker. Cover the beaker to hold the creeping material in when replacing the clipboard on the prop.
- Uncover the beaker and start the stop watch when the creeping material flows across the 0 cm line on the ruler.
- While the creeping material is moving down the board, take readings every half minute for a maximum of 10 minutes.
- Read, to the nearest tenth of a centimeter, the location of the front of the creeping material on the metric scale. Record your observations on the data table.
- After completing the readings, remove the clipboard and set it so the beaker is upright. Peel the creeping material from the plastic sheet, return it to the beaker, and cover the beaker.
- Adjust the clipboard to the next height. Repeat procedures.
Assessment: Completed student answer sheets
Ask the students, "What type of graph would be best to use for the data you just created? Why?" (A line graph would be best because it shows movement over time of the material.)
Have the students create a graph for their data giving little guidance. When finished, have the students share the graphs they created. Ask the students, "What is similar about the graphs? What is different?" (accept all answers) "What makes a good graph?" (Every graph should contain the following elements: a title, labeled axes with the appropriate units in parentheses, axes that start at the origin (0,0), numbered axes in regular intervals (but it does not have to go by ones and the two axes do not have to increase by the same interval), and provide a key if you have more than one line.)
The Dalton School: Graphing Guidelines - http://intranet.dalton.org/departments/Science/Biology1/graph_guidelines.html
Tell the students, "Sometimes, scientists use models to convey their ideas to people. These models have their limitations and do not totally represent what is occurring in real life. For example, a candy bar can be used to illustrate the movement of tectonic plates on Earth's asthenosphere. The movement of the 'tectonic plates' in the candy bar is made by the person holding the bar while the motion of the tectonic plates in Earth is due to the convection currents within the asthenosphere." The limitations of models should be discussed with students.
Assessment: Completed graphs and discussion
Ask the students, "What do the graphs show about creep? (As the angle of repose (height of the board) increases, the material should flow faster.) What does this mean for hill sides? (The steeper the hill side, the more likely material will flow, the faster it will flow.) What would be some real life situations where creep would be an issue?" (accept all answers)
Make sure you stress to students that while each group is doing one trial at different elevations, by having the whole class do the same three elevations, this would constitute repeated trials.
Have students predict what would happen to the graph if the viscosity (thickness) of the material changes. Have students predict what would happen to toothpicks that are placed in a straight line across the material. Students should give their reasons behind their ideas. If enough time, have students explore their ideas.
Assessment: Application of model to real life situations, graph predictions