Transcript Earthquakes
Earthquakes Warm-Up 1. How does the process of subduction recycle rock? 2. How can magma rise up on the ocean floor? 3. What happens to rock to form folded mountain ranges? 4. Explain how Earthquakes occur. 5. How can new ocean floor be created? 6. How do mountain ranges form? 7. Why is density important at subduction zones? An Earthquake is… • The movement of Earth's plates produces strong forces that squeeze or pull the rock in the crust. We feel this as shaking and trembling. • Stress is a force that acts on rock to change its volume or shape • Deformation is the disruption of the original form of rocks 3 Types of Stress There are three different types of stress that occur on the crust, shearing, tension, and compression These forces cause some rocks to become fragile and they snap Some other rocks tend to bend slowly like road tar softened by the suns heat Faults A fault is a break in the crust where slabs of crust slip past each other. The rocks on both sides of a fault can move up or down or sideways When enough stress builds on a rock, the rock shatters, creating faults Faults usually occur along plate boundaries, where the forces of plate motion compress, pull, or shear the crust too much so the crust smashes Strike-Slip Faults Shearing creates a Strike-Slip Fault In this fault, rocks on both sides of the fault slide past each other with a little up and down motion When a strike-slip fault forms the boundary between two plates, it becomes a transform boundary Normal Faults Tension forces in Earth's crust causes Normal faults Normal faults are at an angle, so one piece of rock is above the fault, while the other is below the fault The above rock is called the hanging wall, and the one below is called the footwall When movement affects along a normal fault, the hanging wall slips downward Normal faults occur along the Rio Grande rift valley in New Mexico, where two pieces of Earth's crust are diverging Reverse Faults Compression forces produce Reverse fault This fault has the same setup as a normal fault, but reversed, which explains it’s name Just like the normal fault, one side of the reverse fault is at an angle of the other This fault produced part of the Appalachian Mountains in the eastern United States How Do Mountains Form? The forces of plate movement can build up Earth's surface, so over millions of years, movement of faults can change a perfectly flat plain into a gigantic mountain range Sometimes, a normal fault uplifts a block of rock, so a fault-block mountain forms When a piece of rock between two normal faults slips down, a valley is created Anticlines and Synclines Geologists use the terms syncline and anticline to describe downward and upward folds in rock An anticline is a fold in a rock that arcs upward A syncline is a fold in a rock that arcs downward These folds in rocks are found on many parts of the earths surface where compression forces have folded the crust Seismic Waves Seismic Waves: vibrations that travel through Earth carrying the energy released during an earthquake an earthquake produces vibrations called waves that carry energy while they travel out through solid material During an earthquake, seismic waves go out in all directions to the focus They ripple like when you through a stone into a lake or pond Seismic Waves Ctd. There are three different types of seismic waves: Primary waves, Secondary waves, and surface waves The Richter Scale -The amount of damage created by an earthquake depends on several factors. -Measures an earthquake’s strength Magnitude -Number that represents the measurement of an earthquake on the Ricter Schale