Use students' desks to create an interactive model of sea-floor spreading. Gather two pieces of paper. Ask two students to move their desks together so that they are facing one another and the desks are barely separated. Feed the pages into the opening between the desk and give a top edge to each student. Have the students pull the paper towards their bodies, demonstrating the process of the sea-floor moving out from the spreading zone. Explain that the sea-floor (outer edges of the paper) move toward a subduction zone, where the crust is destroyed.
Create a paper model in class to demonstrate sea-floor spreading. Draw a vertical 4.5-inch line in the center of one piece of your own paper, leaving .2 inches on either side of the line. This is the mid-ocean ridge where new crust is formed. Draw two more vertical lines 1.2 inches from either short edge of the paper for subduction zones. Use scissors to cut these lines open. Draw 11 1-inch wide vertical bands on the other paper. Color in the bands with alternating colors, representing normal and reverse polarity. The far left band is reversed polarity. Cut the second paper in half parallel to the long edges. Thread the strips through the center slit in the first page so that the colors are exposed on the top. Pull each strip toward the outer slit and thread it down through again. Tape the edges of the strips together to form loops and demonstrate sea-floor spreading to the class.
Have each student bring in a clean shoe box from home. Print off the directions from the U.S. Department of the Interior (pubs.usgs.gov) and generate copies for each student and yourself. Cut out each piece of the model with your students, explaining how each piece represents one part of the cycle of sea-floor spreading. Demonstrate for the students how to cut their box and supervise as they attempt to replicate your efforts. Provide colored pencils or markers for students to color their model as desired. Help students to assemble the model and give them tape to hold their "sea floor" together as it rotates through the slits in the box.
Have each student bring in an empty, round oatmeal canister. Hand out a plain piece of white paper to each student. Have them fold their papers in half lengthwise. Cut the papers along the fold line. Cut a 3.5-inch long and .25 inch wide slit in the side of the canister with a serrated knife. This slit represents a mid-ocean rift where new crust is formed. Have the students press the two lengths of paper together and feed them into the slit. Fold the exterior side of the paper over to form a ledge. Have kids gently pull the pieces of paper in opposite directions, pulling the paper out of the canister. This shows how crust spreads from the ridge to the subduction zones for destruction.