Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Where of Plate Tectonics Evidence for Plate Boundaries • Divergent Boundaries – Volcanoes – Ocean Ridges – Seafloor Spreading – Rift Valley • Convergent Boundaries – Volcanoes – Volcanic Mountain Arcs – Volcanic Island Arcs – Mountain Ranges • Transform Fault Boundaries – Earthquakes What is an Earthquake? What Is an Earthquake? Earthquake - vibration of Earth produced by rapid release of energy Earthquake Waves During an earthquake, energy is released in the form of waves. P Waves S Waves Surface Waves Earthquake Waves P waves Are push-pull waves that push (compress) and pull (expand) in the direction that the waves travel Travel through solids, liquids, and gases Have the greatest velocity of all earthquake waves Earthquake Waves S waves Seismic waves that travel along Earth’s outer layer Shake particles at right angles to the direction of travel Travel only through solids Slower velocity than P waves Earthquake Waves Surface waves Seismic waves traveling along Earth’s surface Slowest of the seismic waves Questions About Earthquake Waves 1. An earthquake occurs 100 miles away. In what order will the waves arrive at your location? 2. Which waves do you think are most dangerous? Why? 3. Suggest how earthquake waves have been used to develop our model of the Earth’s interior? Think about what the inside of Earth looks like. Locating Earthquakes Earthquake Waves Seismographs are instruments that record earthquake waves. Seismograms are traces of amplified, electronically recorded ground motion made by seismographs. Locating Earthquakes Earthquake Distance • The epicenter is located using the difference in the arrival times between P and S wave recordings, which are related to distance. Earthquake Direction • Travel-time graphs from three or more seismographs can be used to find the exact location of an earthquake epicenter. Earthquake Zones • About 95 percent of the major earthquakes occur in a few narrow zones. Locating an Earthquake Lab Delineating Plate Boundaries