Profiling Landforms Using a Laser Level

By Trowbridge, John

Abstract. Profiling landforms actively involves students in measuring the topography of landforms such as beaches, hillsides, and stream embankments. In this activity, the author describes how to set up an inquiry situation in which students can ask questions, seek answers, and develop explanations about seasonal or weather- related changes in the landscape. Keywords: barrier island, beaches, erosion, landforms, profiling, stream bank

Have you ever visited a beach or stream and noticed that things look slightly different, but you’re not sure exactly what has changed? Landforms such as barrier islands with beaches and stream banks are dynamic environments that change over time. Whereas changes in mountains can be slow, as when caused by erosion, or dramatic, as from volcanic eruptions, these landforms are not easily accessible to students. However, landforms such as hillsides, stream embankments, and beaches are more easily accessible to students.

Beaches change in response to the action of wind and waves. Storm events can change the topography substantially, but seasonal changes or erosion processes cause more subtle changes. The erosion of beaches and barrier islands receives significant attention because of economic considerations and the storm protection barrier islands offer to land structures and populations. Beaches are extremely expensive real estate (Dean 1999; Rogers and Nash 2003).

Stream embankment stabilization programs are common service- learning activities for schools and civic organizations. The ability to establish baseline profiles with ongoing monitoring would further enhance the quality of such service learning opportunities. Also, urban and suburban sprawl has pushed neighborhoods into areas where hillside slumping occurs. Erosion of the aforementioned landforms can be costly in terms of damage or can impede further development.

The activity presented in this article allows students to recognize the dynamic earth on a measurable microscale compared to larger scale phenomena such as plate tectonics. The activity can be useful in establishing baseline information about landforms and facilitating ongoing monitoring. This type of information is needed to make land use decisions such as zoning and establishing structures, infrastructure, or recreational areas. The activity is similar to surveying because both involve laser sighting, running a transect, and determining elevation.

Through this activity, students will learn that landforms are the result of a combination of constructive and destructive forces, including weathering and erosion. The activity presented in this article addresses National Science Education Content Standard A: Science as Inquiry.

Procedure

Materials

* Two 2-m sections of PVC pipe

* Meter stick or metric measuring tape

* Medium black permanent marker

* Laser level (inexpensive type found in hardware stores)

* Data charts and clipboards

* Pencils

* Graph paper

* Compass

Time Frame

You will need access to a beach, hillside or stream embankment. The activity will take approximately 1-2 hr outside and an additional 1 hr in the classroom.

Preparation

1. Mark one of the poles at the 1-m mark. This is the sighting pole.

2. Mark the middle of the next 2-m pole as 0 and make centimeter marks above and below that point (see Figure 1).

Initiating Activity

1. Ask students what they may know about erosion.

2. Ask students if they have observed an area or landform that has been eroded.

3. Question students about the effects of erosion.

4. Challenge students to invent a method for measuring changes in a particular landform.

Making Measurements

1. Practice or model this activity by profiling a set of stairs or creating an artificial landscape in your classroom using books and placing tarps over desks. Essentially, create a small-scale version of the outdoor activity.

2. Outside, start at the water’s edge and use the compass to establish a perpendicular line, or 90? from the water line to the dunes. If measuring a hillside, stand facing the hill, stretch your arms out to establish a baseline, and establish a perpendicular line. You can use string, rope, other poles, or even ask students to stand to establish and maintain the line.

3. Decide on a measurement interval. If the terrain is flat with little relief, you may want to make measurements every 5 m (see Figure 1). If there are many changes in a short distance, you may want to make measurements every 1 m. Keep track of this on your data chart.

4. Establish one pole as the sighting pole and determine a comfortable point on the pole along which to sight (usually at the 1- m mark).

5. Ask a student to take the other measuring pole away from that point to the measurement interval you established along the perpendicular line. If your measurement interval is 5 m, the student will move 5 m along the established line.

6. Hold the laser level at the sighting mark you chose in Step 4.

7. Aim the level toward the measuring pole and, when the laser is level, switch it on and record the point on the pole that is hit by the laser level (see Figure 1).

8. Move the sighting pole up to the measuring pole’s location. Move the measuring pole out again along the line and stop at the established interval. Repeat until the profile is complete.

9. If it is safe and comfortable to do so, when recording a beach profile, students can make measurements into the water and establish the profile of the underwater part of the beach, including frequently shifting sandbars.

Data Transformation

The data can be transformed into a graph that will reveal the profile of the beach. The data can be recorded on graph paper, in a spreadsheet program such as Microsoft Excel, or in a chart such as Figure 2. Students can generate a profile using the graph function of Excel (see Figure 3).

Student may enjoy creating a graphic profile using 6-10 ft of craft or butcher paper. This amount is large enough that students can place pictures or drawings of the type of plants and animals that live in the various labeled zones found in the beach profile (e.g., foreshore, berm, foot dunes, primary dunes, swales).

Variations

1. Mark the middle of a 2-m pole as 0 and make centimeter marks above and below that point. Use a 1-m pole as the sighting pole and secure the laser level to the top. If a laser level is not available, strong twine and a line level can be used.

2. Part of the lesson can be for the students to figure out how to make the profile measurements with a given set of equipment.

3. The measurements for a stream or hillside may be much closer together than the measurements from a beach.

4. Make miniature scale models of the landforms out of modeling clay.

Further Inquiry

Create assignments on the basis of science scenarios. For example, ask students to prepare written and oral arguments to a simulated town or city council to justify the need for projects to control beach- or streamside erosion. This scenario may include the idea that erosion causes encroachment on existing structures or roads and that the cost of prevention now may be cheaper than the cost of repair in the future. Students could compare summer and winter profiles, compare profiles over several years, or explain patterns in vegetation.

References

Dean, C. 1999. Against the tide: The battle for America’s beaches. New York: Columbia University Press.

Rogers, S., and D. Nash. 2003. The dune book. Raleigh: North Carolina Sea Grant.

JOHN TROWBRIDGE is an associate professor of science education at Southeastern Louisiana University. His main interests include graphic representation of scientific information and marine literacy.

Copyright (c) 2008 Heldref Publications

Copyright Heldref Publications Winter 2008

(c) 2008 Science Activities. Provided by ProQuest Information and Learning. All rights Reserved.