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Candy Faults 1 Name_________________________________ Changing Crust Background Information: Changing the shape of the Earth’s crust depends on two things: c The type of rock layers (strata) c The type of forces acting on the crust. These forces are called deformational forces. There are three basic deformational forces: c Tensional –forces that pull crustal rocks apart at divergent boundaries. They cause rock to get longer. c Compressional – forces that squeeze crustal rock together at convergent boundaries. They cause rock to shorten. c Transversal – forces that push crustal rock horizontally and in different directions at transform boundaries. The cause rock to slip past each other. These are sometimes called shear stresses. These forces create stress, and they act to change the shape and/or volume of a material. Stress causes the build up of strain, which causes the deformation of rocks and the Earth's crust. Sometimes crustal rocks move in the same direction but at different speeds. These forces create faults, folds, and joints. Faults are breaks or cracks along which crustal rocks move. c Normal faults are usually found at divergent boundaries. c Thrust faults are usually found at convergent boundaries. c Strike-slip faults are usually found at transform boundaries. Folds occur when compressional forces are applied to rock that is hot and pliable. c Anticlines are folds in rocks that bend upwards. M. Poarch – 2003 http//:science-class.net Candy Faults 2 c Synclines are folds in rocks that bend downwards. Joints are parallel cracks in rocks. Materials: Small candy bar Paper towel Red licorice sticks Bubble gum Procedure: 1. Unwrap one piece of gum and apply compressional forces with your fingers on the gum. Record your observations. 2. Reshape the piece of gum and apply a tensional force with your fingers on the gum. Record your observations. 3. Reshape the piece of gum and apply a transversal force with your finger on the gum. Record your observations. 4. Repeat Step 3 using the candy bar. Leave your candy bar on the napkin. Observe the effects of tensional forces on different candy bars by looking at the candy bars of 4 students. Record your observations on four different candy bars. Make sure to label the type of candy bar as you record your data. 5. Take your red licorice and stack the sticks horizontally on top of each other, supporting them with your hands. Apply compressional forces by pushing in towards the center. Observe and draw your anticline and syncline. 6. Closure: Clean up any mess on your desk. Throw away the wrappers. You may not leave the room with candy or gum in your mouth! M. Poarch – 2003 http//:science-class.net Candy Faults 3 Data: Effects of Forces Compressional Force Tensional Force Gum Tensional Force Candy Bar _______ Candy Bar _______ Candy Bar _______ Candy Bar _______ Compressional Force Red Licorice M. Poarch – 2003 http//:science-class.net Transversal Force Candy Faults 4 Conclusion: Write a paragraph explain the connections between plate boundaries, forces and faults. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ M. Poarch – 2003 http//:science-class.net