Earthquake and Volcanoes

1. This map shows only the known faults in Oregon. Faults that have moved most recently are shown in red. Earthquake and Volcanoes

5. I. Earthquakes Seismologist A. Earthquake: the shaking and trembling that results from the movement of rock beneath the Earth’s surface. 1. Seismology – the study of Earthquakes 2.Seismologist – geologist that studies earthquakes 3. Stresses causing earthquakes a. Shearing b. Compression c. tension

7. Questions • ____________________________ is the study of earthquakes. • A ___________________________ is a person who studies earthquakes. • Stress at tectonic plate boundaries causes earthquakes. The three types of stress are: • _____________________________ • _____________________________ • _____________________________

8. Questions • Seismology is the study of earthquakes. • A seismologist is a person who studies earthquakes. • Stress at tectonic plate boundaries causes earthquakes. The three types of stress are: • compression • tension • shearing

9. Earthquakes cont. 4. Detecting earthquakes a. Seismic waves – vibrations that travel through the Earth carrying the energy released during an earthquake / Earthquake waves. b. Seismograph – instrument that detects and measures seismic waves 1. Primary Waves – P waves • Push/pull waves (accordion style) • Travel fastest • Travel through solids, liquids and gases

11. Earthquakes cont. 2. Secondary Waves – S waves • Arrive after P waves • Waves vibrate or move side to side and up and down • Travels through solids only 3. Long or Surface Waves – L waves • Slowest moving • Originate on the surface at the epicenter • Rolling or side to side motion • Travels through solids only • A highly simplified simulated recording of earthquake waves (a seismogram) can be seen to the left. Study this sample seismogram and be sure you can identify these parts: • P-waves and the P-wave arrival time • S-waves and the S-wave arrival time • S-P interval (expressed in seconds) • S-wave maximum amplitude (measured in mm)

12.          The seismogram below shows the arrival times of an earthquake’s P -wave and S -wave recorded at a seismic station in Portland ,Oregon.

13. Questions ________________________________ are vibrations that travel through the Earth. _____________________ waves (P-waves) have a ____________________________ motion. S-waves, or __________________________ waves, arrive after the P-waves, and move in a __________________________________ motion. Long or ______________________ waves (L-waves) originate on the surface and have a _________________________________ motion. Fill in the chart by placing check marks in the appropriate boxes that show through which states of matter each type of wave can travel:

14. Questions Seismic waves are vibrations that travel through the Earth. Primary waves (P-waves) have a push-pull motion. S-waves, or secondary waves, arrive after the P-waves, and move in a side to side and up and down motion. Long or surface waves (L-waves) originate on the surface and have a rolling or side to side motion. Fill in the chart by placing check marks in the appropriate boxes that show through which states of matter each type of wave can travel:

15. Earthquakes cont. c.Focus – point beneath the surface where the earthquake begins. d.Epicenter – point on the surface where the earthquake is located. • Directly above the focus • Energy of the seismic wave is the greatest here • The types of rock and soil around the epicenter affect how much the ground shakes. • Most violent shaking occurs here

18. e. Earthquakes occur along fault lines at the edges of the tectonic plates.

19. Questions The __________________ is the point beneath the surface of the earth where the earthquakes originate. The __________________ is the point on the surface of the earth directly above the focus. Earthquakes occur along _____________________ lines on the edges of ____________________ plates.

20. Questions The focus is the point beneath the surface of the earth where the earthquakes originate. The epicenter is the point on the surface of the earth directly above the focus. Earthquakes occur along fault lines on the edges of tectonic plates.

21. Earthquakes cont. Measuring Earthquakes a. Magnitude – is a measurement of earthquake strength based on seismic waves and movement along faults. b.Three ways of measuring earthquakes: • 1.Richter Scale – a rating of the size of seismic waves as measured by a mechanical or electronic seismograph.

23. Earthquakes cont. • Provides accurate measurements forsmall, nearby earthquakes • Less reliable for distance or large quakes 2. Mercalli scale – rates earthquakes according to their intensity. • Not a precise measurement • Describes how the earthquake affects people, buildings and the landsurface

24. Earthquakes cont. • Same quake can have different ratings because of different amounts of damage at different locations. 3.Moment MagnitudeScale – estimates the total energy released by an earthquake. • Rates all size earthquakes, near and far • Example: a magnitude 6 earthquake compared to a magnitude 5, releases 32 times as much energy as a 5 and nearly 1000 times as much as a 4 earthquake. • The Richter scale measures the energy released in an earthquake by measuring the size of the seismic waves. • The Mercalli scale measures the results of an earthquake, such as the shaking and damage that people actually feel and see.

26. Modified Mercalli Scale

27. Questions • What is magnitude? • 2. What are the three ways of measuring earthquakes?

28. Questions • What is magnitude? A measurement of earthquake strength based on seismic waves and movement along faults. • 2. What are the three ways of measuring earthquakes? • The Richter Scale • Mercalli Scale • Moment Magnitude Scale

29. Earthquakes cont. B. Earthquake Hazards and Safety 1. How earthquakes cause damage – the severe shaking produced by seismic waves can cause damage near the epicenter or at great distances. a. Local soil conditions – the thick, loose soil shakes more violently than dense rock b. Liquefaction- occurs when an earthquake’s violent shaking turns loose, soft soil to mud which can sink buildings, or cause landslides

30. Earthquakes cont. c.Aftershocks – an earthquake that occurs after a larger earthquake in the same area d. Tsunamis – tidal wave e. Indirect damage from fire or flooding 2. Monitoring Faults – earthquakes are very unpredictable but certain P & S wave patterns can be monitored. a. seismograph readings

31. Thursday, January 04, 2007 at 08:30:11 UTC Earthquake Location Major Tectonic Boundaries: Subduction Zones -purple, Ridges -red and Transform Faults -green

33. The Richter Scale

35. Earthquakes cont. b. satellite monitors c. laser-ranging devices d. creep meters – wire stretched across a fault to measure horizontal ground movement 3. Making buildings safer a. Location b. Construction methods • Materials used • Building codes

36. Earthquakes cont. 4. Safety a.Drills b. Take Precautions during and after quake c. Preparedness – earthquake kit

37. Questions • What are three things that can cause damage after an earthquake? • Two ways scientists can monitor earthquakes are: • What are two ways to make buildings safer in case of earthquakes? • What are two things people can do to be safer in case of earthquakes?

38. Questions • What are three things that can cause damage after an earthquake? • Loose soil, liquefaction, aftershocks, tsunamis, fires, flooding • Two ways scientists can monitor earthquakes are: • seismograph readings, satellite monitors, laser devices, creep meters • What are two ways to make buildings safer in case of earthquakes? • location, materials used, building codes • What are two things people can do to be safer in case of earthquakes? • safety drills, precautions during and after quake, earthquake kits

39. II. Volcanoes A. Volcano: a weak spot in the earth’s crust where molten material, or magma, comes to the surface as lava. 1. Volcanology – study of volcanoes 2. Volcanologist – geologist that studies volcanoes 3. Volcanoes and Plate Tectonics a. Most volcanoes occur along divergent plate boundaries such as the mid-ocean ridge, or in subduction zonesaround the edges of oceans. Mt. Etna, Sicily (2002-03)

44. Volcanoes cont. b.Magma – molten mixture of rock-forming substances, gases and water vapor from the mantle. Occurs underground. c. Lava – when the magma reaches the surface. d. Hot spot – an area where magma from deep within the mantle melts through the crust like a blow torch. e. Hot spots in the ocean floor createislands such as the Hawaiian Islands

46. Volcanoes cont. e. a volcano forms where magma breaks through the earth’s crust and lava flows to the surface Volcanic vent on the Big Island, Hawaii

47. Questions A volcano is a _______________________________ in the Earth’s ________________ where ________________________ comes through. The study of volcanoes is called ____________________________________________. What is the difference between magma and lava? ____________________________________________________________________________________________________________________________ 4. ________________________ are areas where magma melts through the crust. This phenomenon created the __________________________________.

48. Questions A volcano is a weak spot in the Earth’s crust where magma comes through. The study of volcanoes is called volcanology What is the difference between magma and lava? Magma is molten material below the earth’s surface; lava is molten material on top of earth’s surface. 4. Hot spots are areas where magma melts through the crust. This phenomenon created the Hawaiian Islands.

49. Volcanoes cont. 4. Volcanic Activity a. Inside a Volcano • Magma chamber – pocket of magma beneath the volcano • Pipe – a long tube in the ground that connects the magma chamber to the surface, magma flows through this tube • Vent – opening where molten rock and gas leave the volcano

50. Volcanoes cont. b. Lava flow – the area covered by lava as it pours out a vent. c. Crater – a bowl-shapedarea that may form at the top of a volcano around the volcano’s central vent.