My Science Box

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Summary
This lesson is an extension of the GEMS guide: “River Cutters” by the Lawrence Hall of Science (see note below). In the GEMS curriculum, students are introduced to erosion by modeling the formation of rivers in tubs of diatomaceous earth, a silt-like substance into which meandering river channels and deltas form. This lesson builds off of the River Cutters activities by using a combination of sediment types in the models. They observe how gravel and large particles of sand remain in place whereas silt is washed downstream in fast flowing river channels. In contrast, where the water velocity slows as it reaches the newly forming bay, a beautiful silt-covered delta forms. These observations lead students to the conclusion that fast moving water picks up the smaller sediment particles and eventually deposits them in places where the water slows. Students can then take this theory to test it out in real world conditions at a local creek in the Sediment Study Project, observing sediments and water velocity at different sites along a creek’s length. The concept of how sediments are deposited becomes a core feature of subsequent geology lessons and investigations in which the environmental conditions surrounding the formation of large particled conglomerates may be differentiated from small particled shales and siltstones.

Special Note: This lesson plan is written with the assumption that students have some experience using the river models in the GEMS guide “River Cutters”, written by Cary Sneider and Katharine Barrett and produced by the Lawrence Hall of Science. In this guide, students make observations of rivers carved in just silt (diatomaceous earth), sequencing events in time, noticing patterns, recording information, and acquiring the terminology necessary to describe common erosion patterns. My students completed the first 5 sessions of River Cutters although completing the first 3 lessons is sufficient. So as not to infringe upon the copyright of the GEMS unit, only the extension activity is described here.

Teacher Background
See Erosion Patterns Background for information about erosion and typical sediment deposition patterns.

Summary
In this culminating project, students go out into the field and test their theories about erosion and sedimentation at a local creek. How are sediments distributed along the creek? Does it vary by location (the source, mid-stream, and the mouth)? Does it vary by the velocity of the current? Different classes can collect information for the different study areas. At a study site, they will draw maps, measure the velocity of the current, and collect sediment samples from the creek bed. These samples are analysed back in the classroom for the percent of different sediments they contain. Finally, students stand back and examine their data to try to make sense of the sediments they find. If it is not possible to bring students to a creek, there are many ways to bring the data to them. Collect the sediment samples yourself with photos and water velocity information OR use the Suspended Sediment Database to draw your conclusions. This USGS database provides stream flow and sediment information for over 1,500 rivers and creeks nationwide (see the Going Further section for more information on using the USGS’s database).

Summary
Once students understand the basics of how to read and create a topographic map (see From Maps to Models lesson), students will study and label a topographic map of their local watershed. They will identify the creek closest to their school and mark the boundaries of their watershed. In the process, they practice recognizing hills, ridges, valleys, stream beds and other geographical features on a topographic map. Finally, students take their maps and walk a part of their watershed, matching their maps to their real world surroundings. If a walk through your neighborhood is not possible, the lesson can be conducted without the watershed walk. The watershed walk portion of this lesson may be combined with the Sediment Study Project.

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Activity descriptions and ideas

Summary
Most middle school students have not seen or used topographic maps before. Conceptually, it is difficult for kids to see how a 2 dimensional topo map represents elevation. In this activity, students learn how to create and read topo maps. By the end of the activity, they should be able to read a topo map and identify simple geographical features from a map. Teams of students mold a landform out of clay then place it into a clear plastic container. Water is added to the container in 1 cm intervals and students trace the “shoreline” of their model onto a transparency placed on the box lid. The resulting topo map is traded with another group who is then challenged to turn the 2 dimensional map back into a 3 dimensional landform. Several options are provided for creating the final model based on the materials available to the class. In fact, having more than one option of how to create the model often leads to greater understanding of how topo maps represent elevation.

Summary
This section will give you information to help you plan a field trip with Save the Bay. I brought 32 students to Arrowhead Marsh, a hidden wetland near the Oakland Airport, to meet up with extraordinary Save the Bay Instructors. The day was divided into two parts: 1) Canoeing – where we did water quality monitoring, explored the marsh with all our senses, and went on a wildlife scavenger hunt 2) Restoration – where we repotted 300 native plants, cleaned up the shoreline, and went for a walk on a boardwalk above the marsh. Students were able to explore a wetland up close and observe a leopard shark, feel the Bay’s muddy bottom, and listen to the endangered snowy plover.

Summary
Students go on a web-quest for information on Save the Bay’s Bay Classroom website. They discover facts and information about the part of the San Francisco Bay, its history, the creatures that call it home, and ways they can help protect the bay. This easy activity requires little supervision and is thus offered as a great substitute teacher lesson plan or for one of those teaching days when you need a last minute lesson. Suggestions for making this lesson more interactive are provided.