Materials List: a piece of toast, chart paper, photographs (floods, earthquakes, hurricanes, coastal land loss, erosion, mudslides, volcano eruptions, Grand Canyon), aerial photographs of Louisiana coastline (before and after Hurricane Katrina), empty aluminum soda can, water, access to a freezer, safety goggles, disposable gloves, map of Louisiana, 1 set of each per group (plastic container, limestone, diluted vinegar, painter’s pan, soil, spray bottle), 1 set per student (sand, sealable plastic bags, jumbo chalk sticks, toothpicks), science learning logs
Safety Note: Students should identify the safety precautions necessary when handling acids (wear safety goggles, wear disposable gloves, wash hands after lab) and when handling sand (wear safety goggles).
Introduce the four layers of Earth (crust, mantle, outer core, and inner core) and explain how the crust, which is the layer we live on, is the one that we know the most about. The crust, or Earth’s surface, is constantly changing. Using a piece of toast, demonstrate how rubbing your hand over it causes crumbs to form that can fall when shaken or can easily be blown off. Ask students to brainstorm (view literacy strategy descriptions) a list of the changes in the Earth’s crust that they have seen or heard of, including the damage after a local flood, Louisiana’s coastal land loss, the 2004 Asian tsunami, California mudslides, and the eruption of volcanoes or recent earthquakes. Make a list on chart paper of the student responses. If available, show students’ photographs that illustrate the events above. All of these show the constant processes that are at work changing Earth’s crust. Explore several of these processes with students and have students determine if the event represents a sudden change in the Earth’s crust (within a short span of time—minutes, hours, days) or a gradual change (those taking long periods of time—sometimes many millions of years).
Instruct students to create vocabulary cards (view literacy strategy descriptions) using the following vocabulary terms: weathering, erosion, sediment, sedimentary rocks, metamorphic rocks, igneous rocks, deposit, geology, organic, permeability, evaporation, condensation, precipitation, revolution, rotation, and eclipse.
Example Vocabulary Card
In pairs, have students share their vocabulary cards. Hold a class discussion of the words. The vocabulary cards can be used later as a study aid for quizzes and tests.
Part A: Weathering
Introduce the term weathering. Ask the students if they have ever seen pavement that has buckled. Students will consider what caused this change (tree roots). Relate the buckling to the pressure applied to the rock as the roots grow larger. Encourage students to name other natural agents that could cause rocks to split.
Ask students how they think water could weather a hard rock. The students will model weathering by completely filling an empty aluminum can with water. The students will predict what will happen to the water level and to the can when it is placed in the freezer overnight. The next day the students will observe the level of the ice in comparison to that of the water on the previous day and the condition of the can which may have broken (as the water freezes it may push up and out of the open drink spout). Students will infer how this expansion relates to the weathering of rock. Ask students if the weathering by ice would take a long or short time to breakup a mountain (slow). Ask the students what is created when a large rock is cracked and broken apart (smaller pieces of rock). Explain that the result of weathering is the creation of smaller materials. A video clip from the site below illustrates water freezing in the joints of the rocks at Niagara Falls (go to site and “click on box for streaming video.”)
Have students identify the safety precautions necessary when handling acids. (Wear safety goggles, wear disposable gloves, and wash hands after lab.) To observe how water mixed with acid from decaying plants can breakdown rocks, place several pieces of limestone in a container of diluted vinegar (acetic acid). Direct students to observe the rocks at different intervals and record their observations in their science learning logs (view literacy strategy descriptions). Allow the rocks to sit overnight and then observe the next day. Carefully remove the rocks from the vinegar and observe the vinegar. What is at the bottom of the cup? (Students will observe and conclude that acids help to dissolve away the minerals that make up the rock, creating smaller pieces.)
Have students identify the safety precautions needed when handling sand. (Wear safety goggles) Ask students to design a model of wind weathering using sand, two sealable plastic bags, and chalk. Students should use toothpicks to carve designs in jumbo sticks of outdoor chalk. Place the jumbo stick of outdoor chalk and about a cup of sand in doubled sealable bags and shake the bags vigorously to observe wind weathering. The students should remove the chalk from the bag and observe the chalk sticks after the shaking. Discuss how sand carried by the wind abrades rocks.
Ask students to think of an organism that can further weather a rock once the natural weathering agents have cracked it. Ask them to visualize cracks in the sidewalk. What living thing might they see growing there? (Plants) Students will explain how the roots of plants can crack rocks. In their science learning logs, students should summarize the elements of weathering that have been discussed and demonstrated. Instruct students to describe the ways that rocks or mountains can be weathered. The student should also conclude that the process of weathering is a slow process.
Part B: Erosion
Ask the students if they have ever found leaves in their yard that came from a neighbor’s tree. Have the students explain how the leaves got there. Just as the wind carries leaves, it also carries and moves weathered rock. Question students as to if they have ever seen television programs that showed people walking in sand storms. Explain to students that the small pieces of sand are actually pieces of weathered rocks. Introduce the term erosion. Explain to the students that weathering and erosion work together to tear down some landforms while forming others in different locations. Use a map of Louisiana to show the Mississippi River Delta and explain to the students how the sediment that forms the delta is carried by the water of the Mississippi River. Ask the students to think of other natural agents of erosion that they may have observed at home. (They may suggest water running down their driveways, rain eroding hills, muddy water in ditches after a rain.)
Using a painter’s pan, the students will model a riverbed. Press a layer of soil on the pan. Ask students, “If we make it rain on the land, what do you think will happen to the land?” Pour or spray water with a spray bottle near the highest part of the pan to mimic rain. Allow students to observe how the water can move weathered material downstream. Ask students what force is pulling the material down the hill (gravity). If the students do not know this, the teacher will introduce the term at this time. The students may question how the amount of incline of the pan affects erosion. Allow students to design an additional investigation to explore this idea. Students should present their methods of testing the hypothesis to the group and the group will determine the best design. After the students perform the investigation they should repeat the activity changing the incline of the pan to test the effect of steepness of the hill and water speed on erosion. The students will record the data in a table created in their science learning logs, make careful measurements of the incline changes, and draw conclusions. Students should conclude that the steeper the hill the faster the water runs down the land. The faster the water runs down the land, the more land the water can potentially erode.
Show students pictures of the Grand Canyon. Have students explain how the canyon became so deep. Ask students if this was a slow or fast process (slow). Show students aerial photos of the Louisiana coastline before and after Hurricane Katrina. Have students identify the differences in the pictures. (Students should note the significant amount of land loss associated with this storm.) Ask students if this was a slow or fast process (fast). In their science learning logs, students should summarize the elements of erosion that have been discussed and demonstrated. Instruct students to describe the ways that rocks or mountains can be eroded. The student should also conclude that the process of erosion can be both a slow process and a fast process.