There are several materials you will need in order to complete this lesson. These materials are easy to obtain, and may even be in your classroom already. These materials are:
Have students sit on the floor in a circle and tell them that we will be exploring the uppermost layer of the earth over the next few weeks. Show students that the earth is made up of four layers (crust, mantle, outer core, and inner core). Give each student a piece of red modeling clay. Have students roll the red clay into a ball. Give each student a square of wax paper to put their ball on. Hand students a piece of orange clay. Have students roll the clay into a ball and then press it into a disc about 1/8 inch thick. Have students wrap the red ball in this orange layer and place it on the wax paper in front of them. Hand each student a piece of brown clay and have them repeat step 2, but make the disc about ¼ inch thick and wrap it around the ball. The final piece of clay is green. Have students make a very thin disc, just enough to cover the ball.
When students have completed making their balls, hand each student a plastic picnic knife. Students will gently cut their balls in half with a sawing motion so as not to distort the shape or layers inside the ball.
Have students observe their own layers and compare and contrast them with those of other students. There will be some variation, use this as a vehicle to discuss how the earth’s surface will look different in different parts of the world and will change over time.
Have students cut a small slice to show the layers and place it into a zip-closure baggie to put into their science journals, put them aside for now.
Show students a slice of toast. Rub your finger across the toast and demonstrate how rubbing your hand over the toast causes crumbs to form. These crumbs can easily fall or be blown off the surface of the toast.
Ask students to brainstorm ways that they have seen the crust of the earth change. This could be due to an earthquake rippling or cracking the earth, a flood from a tsunami or river, river banks moving backwards and/or falling into the river, sidewalks or roads heaving, etc. Write student responses on chart paper. Once students have had a chance to brainstorm, explore several of these examples and ask students if these are rapid changes (minutes, hours, days) that occur or those that occur over time (years, sometimes millions of years).
Introduce the vocabulary terms:
weathering, erosion, sediment, sedimentary rocks, metamorphic rocks, igneous rocks, deposit, geology, organic, permeability, evaporation, condensation, precipitation, revolution.
Give student pairs a vocabulary card and have them discuss its meaning. Have student pairs share their word and define them for students. Students can write these vocabulary words into their science notebooks during vocabulary practice time or bell work.
Introduce the word: weathering. Ask students if they have ever seen pavement buckled. Have them discuss what they think might have cause the buckling: tree root, ice heave, etc. Ask students what would happen to the pavement if the tree root grew larger. Encourage students to think of other natural processes that could split pavement or rock.
Ask students how they think water could weather rock. Have them brainstorm what might happen. Partner students in pairs and hand them an empty aluminum soda can. Have students fill the can completely. Have student pairs predict what will happen to the water in the can, as it freezes overnight. Students will make observations the following day.
Students will observe that the can might break. They may observe that as the water freezes, it might come up through the opening in to top of the can and spill out. This demonstration will allow students to observe the expanding characteristic of water as it freezes. Students will be able to infer how this might affect a rock over time, and how mountains may be affected by this process over the course of time.
Have pairs of students wear goggles and gloves to complete this next demonstration. Give each pair of students a piece of limestone and some vinegar in a clear, plastic cup. Have students carefully place the limestone in the vinegar and observe what occurs. Students should observe that bubble form on the limestone. Have students leave the limestone in the vinegar over night and make further observations the following day. There should be sediment in the bottom of the boat.
Have students continue to wear the goggle and gloves. Give each pair a piece of sidewalk chalk , ½ a cup of sand, and two zip closure plastic bags. Have students draw a design in the chalk, place the chalk and the sand in one bag, close it, and double-bag it. Have students observe. Have students shake the bag for 5 minutes and then make observations of any changes that occurred. Students should see that the chalk has begun to break down. Their design should have degraded as well.
Ask students to think about what organisms may further deteriorate these processes – plants may grow in these cracks and further enlarge the cracks.
In their science notebooks, students should summarize the processes of weathering they just demonstrated. Students will describe how these processes will influence mountains and rocks. Students will ask an “I wonder” question about erosion. I wonder how erosion affects the earth’s surface?” I wonder if erosion is similar to weathering?” “I wonder if erosion is stronger than weathering?” are some questions students might think of. Use these questions to stimulate discussions in the following lesson on erosion.
Assessment will be done using the student-generated observations written on the observation graphic organizer. In addition, student understanding will be assessed through the answers written for their exit tickets.
Students' answers will help define mechanical weathering and chemical weathering in their own terms, rather than me giving them the answers. We will define weathering later, in a more formal manner.
Exit tickets are very useful as a quick, easy formative assessment to help plan for the next lesson. They help me understand how well the lesson went, and the level of understanding of the topic covered.