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Objectives F.2.1.1. Explain how stress in the crust changes Earth’s surface. F.2.1.2. Describe where faults are usually found and why they form. F.2.1.3. Identify the land features that result from plate movement. Stress Stress is a force that acts on rock to change it’s shape or volume. The energy is stored in the rock until changes shape or breaks. This is where earthquakes come from. There Are 3 Types of Stress Tension Compression Shearing Types of Stress Tension, compression and shearing work over millions of years to change the shape and volume of Earth’s crustal rocks. Tension Tension pulls the crust apart making it thinner in the middle. Tension occurs where two plates are moving apart. Can you give me an example of a location where tension is the dominant stress? Mid Atlantic Ridge Compression Compression squeezes rock together until it folds or breaks. Can you think of places where compression is the dominant stress? Plates Converge Continental/Oceanic Continental/Continental Shearing Shearing pushes rock in opposite directions. Can you think of a place where shearing is the dominant stress? San Andreas Fault The San Andreas Fault lies along the California coast. The Pacific Plate is pushing north at a couple of inches a year. San Andreas Fault Kinds of Faults Most faults occur along plate boundaries where the forces of plate motions push or pull the crust so much that the crust will break. The 3 types of faults are: Normal Fault Reverse Fault Strike Slip Fault Normal Fault In a normal fault, the hanging wall slides down the foot wall. What kind of stress is acting on a normal fault? Tension Reverse Fault In a reverse fault, the hanging wall pushes up and sometimes over the foot wall. What kind of stress produces a reverse fault? Compression Strike-Slip Fault In a strike slip fault, the rock slide past each other in opposite directions. What kind of stress causes a strike slip fault? Shearing Changing Earth’s Surface Over millions of years, the forces of plate movement can change a flat plain into landforms such as anticlines and synclines, folded mountains, fault block mountains, and plateaus. Folding Earth’s Crust Syncline Anticline A fold of rock that bends downward to form a valley. A fold of rock that bends upward to form a an arch. Syncline and Anticline Fault Block Mountains When two normal faults are parallel to each other, a fault block mountain will form as the rock between the faults rises upward and the faults slip down. The Colorado Plateau Colorado Plateau Plateau A plateau is a large flat area elevated by uplift to high above sea level. The Grand Canyon The Grand Canyon lies in the Colorado Plateau and has been carved out of the plateau over millions of years by the Colorado River. Do you know what the process of a water carving out rock is called? Erosion The Grand Canyon