P a g e 1 Name A Fault Model Purpose: To explore the types of faults and how they affect the geosphere Background Information: A fault is an area of stress in the earth where broken rocks slide past each other, causing a crack in the Earth's surface. Faults are often (but not always) found near plate boundaries. Each type of fault is often related to specific types of plate movements. Normal faults are often associated with divergent boundaries. o Create space. Two blocks of crust pull apart, stretching the crust into a valley. o One block of land slips downward in relation to the block of land on the other side of the fault zone o Fault motion is caused by tensional forces and results in extension. Thrust or reverse faults are often associated with convergent boundaries. o Slide one block of crust on top of another. These faults are commonly found in collisions zones, where tectonic plates push up mountain ranges. o The land is compressed and one side of the fault moves upward. o Fault motion is caused by compressional forces and results in shortening. Strike-slip faults are often associated with transform boundaries. o Rocks are sliding past each other horizontally, with little to no vertical (up and down) movement o Fault motion of a strike-slip fault is caused by shearing forces. o Transform faults are a special type of strike-slip fault. Most are found on the ocean floor. They commonly offset active mid-ocean ridges, producing zig-zag plate margins. Earthquakes are common along these faults. usgs.gov Use a highlighter to mark the most important parts, or the parts you want to remember in the background information. Materials: Model Map pencils Glue Scissors
P a g e 2 What to do: 1. Color the fault model according to the color key. 2. Cut out the fault model and fold each side down to form a box with the drawn features on top. 3. Tape or glue the corners together. This box is a three dimensional model of the top layers of the Earth's crust. 4. The dashed lines on your model represent a fault. Carefully cut along the dashed lines. 5. You will end up with two pieces. 6. NORMAL FAULTS a. PREDICT what will the land look like after an earthquake caused by a normal fault? Sketch your prediction below. b. MODEL A NORMAL FAULT i. Locate points A and B on your model. ii. Move point B so that it is next to Point A. iii. Observe your model from the side (its cross-section). c. Draw what the land looks like after an earthquake caused by a normal fault as represented by the model you have just constructed.
P a g e 3 Questions: 1. Which way did point B move relative to point A? 2. What happened to rock layers X, Y and Z? 3. Are the rock layers still continuous? 4. What likely happened to the river? The road? The railroad tracks? Explain your answer. 7. THRUST FAULTS a. PREDICT what will the land look like after an earthquake caused by a thrust fault? Sketch your prediction below. b. MODEL A THRUST i. Locate points C and D on your model. ii. Move Point C next to point D. iii. Observe the cross-section of your model.
P a g e 4 c. Draw what the land looks like after an earthquake caused by a thrust fault as represented by the model you have just constructed. Questions: 1. Which way did point D move relative to point C? 2. What happened to rock layers X, Y and Z? 3. Are the rock layers still continuous? 4. What likely happened to the river? The road? The railroad tracks? Explain your answer. 8. STRIKE-SLIP FAULTS a. PREDICT what will the land look like after an earthquake caused by a strike-slip fault? Sketch your prediction below. i. Locate points F and G on your model. ii. Locate points F and G on your model. iii. Move the pieces of the model so that point F is next to point G. b. Draw what the land looks like after an earthquake caused by a strike-slip fault as represented by the model you have just constructed.
P a g e 5 Questions: 1. If you were standing at point F and looking across the fault, which way did the block on the opposite side move? 2. What happened to rock layers X, Y, and Z? 3. Are the rock layers still continuous? 4. What likely happened to the river? The road? The railroad tracks? Explain your answer. Conclusions 1. What happens when forces are applied to a model of the Earth? a. Tension - b. Compression - c. Shear - 2. How much surface movement occurs with each type of force? a. Tension - b. Compression - c. Shear - 3. Why do earthquakes occur?
P a g e 6 Adapted from: USGS Learning Web A Model of Three Faults http://interactive2.usgs.gov/learningweb/teachers/faults.htm