BSCS Science Tracks: Connecting Science & Literacy Second edition, 2006 by BSCS Investigating the Changing Earth Unit Overview 5415 Mark Dabling Blvd. Colorado Springs, CO 80919 719.531.5550 www.bscs.org
Module Overview Introduction to Investigating the Changing Earth Students generally assume that their outdoor environment remains constant. Unless the devastation of a flood or the tragedy of a large earthquake has affected them, students do not think of Earth s surface as something that constantly changes. This is due, in part, to the fact that many changes to the surface of Earth happen on the grand scale of geologic time, measured in millions of years, which has little meaning to a child. And, while catastrophic changes to Earth s surface earthquakes, volcanoes, and landslides have always captured students interest, smaller changes are harder to observe. If students become aware of the kinds of changes that happen to Earth s surface, however, they can begin to develop an understanding of the incremental steps that have led to the formation of the familiar landforms that they see in today s landscape. Module Overview The Investigating the Changing Earth module introduces students to the concepts of weathering and erosion and the difference between the two. They learn that weathering, primarily from the effects of wind and water, causes the breakdown of earth materials. Module Overview 21
Erosion, on the other hand, refers to the transport or carrying away of the weathered particles. As students discover in their activities, the weathered particles quickly or gradually move downhill. This downhill motion can occur quickly in the form of a landslide or a rock slide, or it can be part of a slower process involving complex systems of streams or glaciers. Once students understand the ways in which earth materials are weathered and eroded, they are ready to simulate some changes to Earth s surface that are hard to observe in real life in a short amount of time. In this module, students construct a stream table to model the erosion caused by the downhill movement of water. By taking time to experiment with the model by changing water flow patterns and observing the resulting erosion, students form an understanding of streams. They compare their observations of erosion in the stream table with what they have seen on the surface of Earth and develop explanations for stream-related phenomena such as the deposition of deltas, formation of canyons, and causes of floods. Students develop an understanding of models as important tools that scientists use to learn more about Earth. Not to ignore the catastrophic occurrences that always capture students attention, this module includes a volcano demonstration. However, rather than just ooh and ah, students of this level are encouraged to analyze 22 Investigating the Changing Earth
the validity of the model. Is it one that scientists might use to learn more about volcanoes? Can experimentation with the model help scientists predict what might happen in the real world? As they complete the lessons in the module, students discover that some models are better than others as tools for studying the real world. By the end of the module, students should realize that rock material is recycled. By participating in activities in the module, they will have explored most of the processes that make up what is often referred to as the rock cycle weathering, erosion, deposition of sediments, and new rock formation. Because these processes are difficult to observe, as are many geologic processes, students learn about the recycling of rock material by combining their observations from earlier activities with information given to them in a fictional story. In this way, students begin to form the concept of the ongoing nature of the breaking down and building up of the surface of Earth. You might note that we do not use the term rock cycle with students in explaining the changes that rocks go through. This is because the process is complex and the term implies that rocks cycle in a closed system. Rather than give a label to the complex process through which existing rocks can become new rocks that weather and erode again, we chose to use the term recycled to indicate that, when rocks break down, the rock particles are used again in the formation of Module Overview 23
new rocks. However, that process is not always cyclical for any one rock particle. We feel it is more important for students to understand the ongoing nature of the processes that break down and build up the surface of Earth than for them to attach the label of the rock cycle to those processes. Students often are interested in where they fit into the natural processes that surround them. In this module, students look at the changes to Earth s surface that humans make and discuss the positive and negative results of those changes. By the end of the module, students are able to depict a change to Earth s surface, either natural or human-made, and describe what the surface of Earth looked like before the change happened, what actions caused the change, whether the change was fast or slow, and what the feature might look like after the change. Through these and many other handson experiences, students come to understand that the surface of Earth is constantly changing. In addition to enabling students to construct their understanding of Earth s surface changes, the lessons in this module provide students with hands-on, minds-on learning experiences; critical-thinking and inquiry skills; 24 Investigating the Changing Earth
conceptually developmental and sequenced experiences; literacy strategies in reading, writing, listening, and speaking; opportunities to learn collaboratively with other students; and integrated activities that encourage curiosity and imagination. See Module at a Glance for a summary of the lessons and the development of the concept of the changing Earth. Conceptual Outcomes The following table illustrates the priority placed on conceptual development in the module and also displays the correlation of the module s conceptual outcomes with the content standards in the National Science Education Standards and the Benchmarks for Science Literacy. Module Overview 25