BY SARAH J. FICK AND JONATHAN BAEK

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Natalie April Roberts
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1 24 BY SARAH J. FICK AND JONATHAN BAEK

2 CONTENT AREA Earth and space sciences GRADE LEVEL 6 8 BIG IDEA/UNIT Earth s systems. ESSENTIAL PRE-EXISTING KNOWLEDGE Basic water cycle processes and vocabulary Gravity and forces Map navigation and symbols Measurement skills and tools Helpful: Energy (kinetic potential, and thermal) TIME REQUIRED Varies, depending on which activities you implement. Eight class periods of instruction are described. COST Varies, depending on which activities you implement. Each activity can be modified according to the resources available. February

As part of a middle school unit on the flow of water on and through the Earth s surface, students use multiple models to represent the factors that influence water flow within watersheds.

3 As part of a middle school unit on the flow of water on and through the Earth s surface, students use multiple models to represent the factors that influence water flow within watersheds. This article shows how the unit incorporates a variety of tools (including models and digital and paper maps) to help students make sense of the content using a variety of data sources. The unit also encourages students to have a more flexible understanding of the concept of water flow. In this article, the word model is used to mean any simplified representation of the landscape. In these activities, a model can be a topographic map, an online map, a digital elevation model, or a physical representation. The term conceptual model is intended to mean students drawings of their current understanding of the system. One of the key components of the unit is the use of conceptual models periodically throughout to gauge students understandings. Conceptual models are based on student understanding and are expected to become more sophisticated over time. As students learn additional information about watersheds and the movement of water, they are asked to draw a new conceptual model representing their understanding. These conceptual models show the progression of students ideas during the unit, and can be used by the teacher to support students by illustrating their changing understanding and highlighting any areas of confusion. One challenging but key component is supporting student understanding of how elevation combined with the force of gravity influences the flow of water. Students are often familiar with the fact that water flows down, but understanding the presence of subtle elevation changes in the larger landscape is not easy for many students. One of the goals of the unit is to help students understand the influence of elevation changes, large and small, on the flow of water. Students often think that areas with less elevation change are flat, and as a result, the water does not travel. Students in North America often also hold misconceptions about the direction of water flow. For example, they may believe that all rivers flow south or water gets absorbed by the ground and doesn t travel. These statements are not Materials for experience oz. piece of modeling clay/play dough per group 2 meter sticks per group 1 wire clay cutters per group Total cost: Approximately $11.75/group ($10.50 per group is reusable; might need to buy replacement modeling clay/play dough) always false, but over-application to inappropriate situations leads to misconceptions. In our experience, students often hold these misconceptions and watershed-specific misconceptions (e.g., watersheds only consist of bodies of water, not the land that surrounds them; watersheds are sheds that hold water). Description of activities One of the primary goals for the beginning activities is for students to understand how the water cycle interacts with the Earth and to connect students knowledge of their local geographic context to the FIGURE 1: ESRI terrain profile tool output The ESRI terrain profile tool allows you to trace a line on a map with topographic data and translate that map into an elevation profile. 26

4 SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION concepts of elevation and gravity. In the beginning lessons, students revisit the concept of the water cycle, which many students had learned the basics of in earlier grades, and apply it specifically to the state of Michigan. The beginning part of the unit is framed around these questions: What happens when it rains in the state of Michigan? Where does the water go? This article summarizes activities that helps middle school students understand the flow of water on and through the Earth s surface. We suggest providing students with an initial formative assessment, such as the one described in this article, to determine which of these activities might give your students a more thorough understanding of a watershed system and the energy that drives the movement of water. Differences in school context and student experience might mean that your students have a different grasp of elevation and how it is represented or how slope dictates the flow of water. Engage: ESRI digital elevation tools (one class period; minutes) To begin the unit, students examine their local environment. Focusing on Michigan at a state level, we examine how water moves on the surface at a broader scale. It is our intention that this initial activity engages students prior knowledge and understanding by exploring a familiar area. Students use the terrain profile tool in the ESRI web GIS platform to view the elevation along the length of a river (see the lesson description for full directions; see Resources for a link to the online tool). The web version of the ESRI software does not require any specialized software and can be used on any device with internet access, although use of the tools may be easier on a computer than a tablet. The terrain profile tool allows you to create a line segment that can follow any geographical feature. In this case, we draw a line that follows a river (Figure 1). This allows students to observe the slow decrease in elevation as the river makes its way to the destination. Determining the flow of a river is not intuitive for all students. In the first iteration of the unit, we had students predicting that the destination of a stream was actually the headwaters that formed the stream because the headwaters were south of the destination of the river. This is just one example of how students misconceptions about the flow of water might play out in a data analysis activity. Unless students are shown evidence that the process is not feasible, they sometimes have a hard time overcoming their belief in prior knowledge. After the teacher demonstrates following one river together as a whole class, students are free to explore a different river on their own. In table groups (3 5 students per table), students are assigned wellknown rivers around the whole state, and use the search features described in the ESRI tool to zoom into that area. In this activity, students make predictions about the direction of flow based on the map, and then check their predictions by looking at the elevation profile for the river. After each group examines their river, students highlight their river on a state map projected on the whiteboard and indicate the direction of flow of the river they examined. Observing the trends in the rivers overall allows for a class discussion that focuses on themes in how the rivers move. While this activity helps students see the relationship between elevation and water flow, students are focused on the bodies of water themselves, not the land that drains to the body of water. For students to understand how water gets to bodies of water within a watershed, we need to support their understanding of how elevation is represented in various types of models. To do this, students create a model landscape and its related topographic map. Experience #1: Modeling elevation using physical models (two class periods; min.) Students often have a difficult time understanding what topographic lines represent. To help students see precisely what an individual topographic line represents, we have them create a 3-D model of a mountain out of clay (or play dough) and then we physically convert that mountain into a 2-D representation, creating the topographic map for that mountain. The activity begins with a basic clay mod- February

5 el of a single peaked mountain, with a steep side and a more gradual side. Students work in small groups (3 5) at tables with a small bag of modeling clay (8 12 ounces) and are given initial instructions to shape the mountain. For safety, it is recommended that students wear goggles while working with the Play- Doh or clay models and wash their hands afterward. Next, so as to provide proper alignment of the mountain during the activity, students are instructed to create a cardinal grid by carefully imprinting the clay with a pencil for North-South/West-East perpendicular dotted lines, as well as extending and drawing it on the paper. After students design their mountains, they segment the mountain into slices of equal height using wire clay cutters (a thin piece of wire used for slicing clay, but not sharp for students). Two meter sticks, lying flat on either side of the mountain, provide a consistent height (~ 1 cm) for the wire cutters to follow as it slices through the clay. A firm side-to-side motion, while pulling from the farthest side inward toward the student, works best to create consistent slices. Students continue this until the mountain is completely segmented. After students slice each piece, they trace the outline of the FIGURE 2: A sliced modeling clay mountain next to its topographic map Here, the slices are laid out next to one another with the topographic map constructed using an outline of the different layers. slice onto paper, making sure to align the segment according to the cardinal grid that was originally drawn. As students remove each layer, they produce a topographic map (Figure 2). The steep side and the gradual side of the clay mountains illustrate for students how differences in slope are represented using a topographic map. Variations of this activity can also include adding watershed features (rivers, lakes) to students clay mountain and observing how those features are represented in the contours, as well as changing the contour interval to increase or decrease the height at which you slice the layer. Students compare the created 2-D topographic map to the 3-D clay model to see evidence of how differences in elevation changes are represented on the topographic map (Figure 3). Students are also asked to show how water would flow on their mountain. This information is represented using arrows on the topographic map of their mountain (Figure 3). When students can easily identify which areas are steep or which direction a river flows from the contour lines, it allows students to work with a greater variety of data types to analyze the watershed boundaries and how water moves in a geographic area. Students can also apply these concepts to interpreting topographic maps of other locations. Experience #2: Paper topographic maps (two class periods; min.) Topographic maps of a local area can help students identify major factors that influence how water will flow in that area. To support students in making and checking predictions about the flow of water on the surface of the Earth, we print several topographic maps (available through the USGS map service; see Re- 28

SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION FIGURE 3: Clay mountain with topographic map The equal height slices of the modeling clay mountain are

FIGURE 4: A laminated topographic map with water flow predictions On the annotated map, the class designated mountainous areas with inverse Vs, and then predicted the direction of the water flow.

6 SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION FIGURE 3: Clay mountain with topographic map The equal height slices of the modeling clay mountain are shown next to the corresponding topographic map. The topographic map has arrows on it showing students predictions about the direction of water flow on this mountain. FIGURE 4: A laminated topographic map with water flow predictions On the annotated map, the class designated mountainous areas with inverse Vs, and then predicted the direction of the water flow. Finally, the map includes lines that show that higher elevation divides the flow of water. sources) and laminate them to make them reusable, allowing students to mark the maps with dry-erase pens (Figure 4). We choose a local river and ask students to find different points of elevation (e.g., lowest, highest, greatest slope change, gradual changes) and then ask which direction water will flow from any spot the teacher identifies on the map. Because students are already familiar with topographic lines and how they can indicate which direction water flows (the rule of inverse Vs: When there is a V in a topographic line with a river in the center of the V, the V will generally point uphill), we ask them to identify on the map some instances where these indicators could be seen, and as an efficient formative assessment, we have them circle an example on the map and indicate the direction of water flow. Experience #3: Digital topographic maps (one class period; min.) ArcGIS Online also has other tools that students can use to analyze the hydrology of an area. One of these tools is a wide variety of map layers available within the user community. We found several hy- February

FIGURE 5: A Digital Elevation Model A Digital Elevation Model (DEM) can use colors to show which areas of the landscape have higher and lower elevation relative to the surrounding areas.

The student shows a watershed boundary, which incorporates many smaller bodies of water and the land that surrounds them. Written words show the areas of higher and lower elevation in this model.

7 FIGURE 5: A Digital Elevation Model A Digital Elevation Model (DEM) can use colors to show which areas of the landscape have higher and lower elevation relative to the surrounding areas. FIGURE 6: A student s final conceptual model of a watershed This model focuses more closely on the aspects of a watershed that closely align with systems. The student shows a watershed boundary, which incorporates many smaller bodies of water and the land that surrounds them. Written words show the areas of higher and lower elevation in this model. drology layers for the state of Michigan, with varying amounts of detail. There was one statewide layer that also included local streams, which seemed like it would support students learning. We would recommend that you search within ESRI s data layers for a hydrology layer for your own state. A key crosscutting concept that is important for supporting student learning is that watersheds are systems. The various components of this crosscutting concept (inputs, outputs, boundaries, nested systems, and interactions) can be illustrated by using ArcGIS as well as other online resources such as topographic-map.com (see Resources), which allows the user to see topographic data using different display techniques. (See also Fick, Arias, and Baek, forthcoming.) Within ArcGIS Online, there are multiple map layers that can outline established watershed boundaries, highlight hydrological features, and provide tools to measure and mark on the map. Our students first research a local creek, where we use ArcGIS to help identify and outline the tributaries and the areas of land that feed into those bodies of water. From this, students identify the output of the local creek and make connections to how it also contributes to the larger Huron River watershed basin. The concept of nested systems, a set of smaller systems that together form a larger system, becomes more accessible when students can trace where the Huron River feeds into Lake Erie at the output of the river, and how that body of water connects to others, eventually reaching the ocean. Elaborate: Digital elevation models (two class periods; min.) As part of a summative synthesizing project, students apply what they learned about the local area to a different area anywhere in the world. Students are given the freedom to choose any geographic area that interests them, and they use the tools we used in class to analyze the topography. These tools, as well as the digital elevation model (DEM) available on topographic-map.com, help students develop an understanding of how water moves on the surface of the Earth in less familiar environments; 30

8 SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION students eventually create a report about a watershed in that region. Students are assessed on being able to identify components of watersheds (boundaries, inputs, outputs, interactions), as well as the quality of their created model. A rubric is provided for students to understand all of the objectives required (see the rubric in the Online Supplemental Materials). DEMs use detailed elevation informa- Connecting to the Next Generation Science Standards (NGSS Lead States 2013) The chart below makes one set of connections between the instruction outlined in this article and the NGSS. Other valid connections are likely; however, space restrictions prevent us from listing all possibilities. The materials, lessons, and activities outlined in the article are just one step toward reaching the performance expectations listed below. Standards MS-ESS2.4: Earth s Systems Performance Expectations MS-ESS2.4: Develop a model to describe the cycling of water through Earth s systems driven by energy from the sun and the force of gravity. DIMENSIONS CLASSROOM CONNECTIONS Science and Engineering Practices Analyzing and Interpreting Data Developing and Using Models Students use topographic maps and digital models of elevation to determine the slope of the landscape and then use that information to predict the direction of the flow of water. Students create conceptual models to show their understanding of the watersheds and the flow of water through a landscape. Disciplinary Core Ideas ESS2.C. The Role of Water in Earth s Surface Processes Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill flows on land. Global movements of water and its changes in form are propelled by sunlight and gravity. Students use models of elevation to predict the flow of water based on knowledge of the downhill flow of water caused by the force of gravity pulling the water down the slope of the landscape. Crosscutting Concept Systems and System Models Students determine the boundary, inputs, outputs, processes, and nested systems for a particular watershed, and draw conceptual models identifying the components of the watershed. February

9 SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION tion to create a layer of elevation where every pixel or point (depending on the data used to make the data layer) is assigned an average elevation for that area. These data can then be represented using a color gradient to show the elevation for each location as a color, making it easy to identify higher and lower elevation locations (Figure 5). The DEM helps students quickly visualize the elevation changes for the geographic area they select. The color gradients help students see changes in elevation and provide a clearer visualization for students to use in order to convert 2-D maps that are available for their locations into the 3-D model that they have to create for their project. The resource also allows users to click on a specific location and provides the elevation for that location, which helps to determine the direction of water flow. Evaluate: Understanding student learning (incorporated into lessons throughout the unit) Throughout the activities, students are asked to draw what a watershed looks like. Similar prompts are used throughout the unit, and students are prompted to think about how their current drawing is similar to and/or different from their previous drawing. Students drawings slowly evolve over time to incorporate some of the elements being described in class. At the end of the unit, students are asked to complete one final drawing showing their understanding of a watershed for a unit test. Figure 6 shows an example of student work at the end of the unit. This image show students final understanding from the unit. In this conceptual model, you can see students representing movement of water on and through the surface of the Earth, with elevation and sometimes gravity pulling the water downhill or into the layers of the Earth s surface. The image shows the boundary of the watershed existing in areas with higher elevation, and sometimes watersheds nested within other watersheds. Students represent the areas of higher elevation through various methods, including labels, side profile drawings, and inverse Vs. All of these means of representing the concept contribute to a thorough representation of the content when used with labels of water flow and other representations. See the Online Supplemental Materials for a rubric to evaluate students models. This article shows how the use of a variety of models requires students to make sense of the same concept using a variety of data sources. Students are able to use digital and analog resources to make sense of the same content. We found that it is important for students to see multiple modeled representations of elevation to fully understand how elevation influences the ways that water moves on and through the surface of the Earth due to the force of gravity. REFERENCES Fick, S., A.M. Arias, and J. Baek. Forthcoming. Unit planning using the crosscutting concepts. Science Scope. NGSS Lead States Next Generation Science Standards: For states, by states. Washington, DC: National Academies Press. RESOURCES ESRI Terrain Profile Tool esriurl.com/elevation Free US K 12 Educational Accounts connected United States Geological Survey (USGS) store store.usgs.gov (select local topo quads in 7.5 x 7.5 scale) USGS topographical maps ONLINE SUPPLEMENTAL FILES Rubric for evaluating students watershed drawings www. nsta.org/scope1702 Watershed project rubric Worksheet one: ESRI digital elevation tools scope1702 Worksheet two: Creating a clay model scope1702 Sarah J. Fick (ficksj@wfu.edu) is an assistant professor of science education in the Department of Education at Wake Forest University in Winston-Salem, North Carolina. Jonathan Baek is a middle school science teacher at Honey Creek Community School in Ann Arbor, Michigan. 32

Introduction to Contour Maps

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