The Movement of Ocean Water

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  • 1. The Movement of Ocean Water Earth Science: Book H, Chapter 3
  • 2. Warmup What are some ways that people can move around the ocean?
  • 3. Section 1: Currents By the end of this section, you should be able to: Describe surface currents. List the three factors that control surface currents. Describe deep currents. Identify the three factors that form deep currents.
  • 4. Surface Currents Ocean water contains stream-like movements of water called ocean currents. Norwegian explorer Thor Heyerdahl proved his theory that ocean currents influenced human migration by using a raft that was powered only by wind and ocean currents.
  • 5. Surface Currents Horizontal, stream-like movements of water that occur at or near the surface of the ocean are called surface currents. Surface currents are controlled by three factors: global winds, the Coriolis Effect, and continental deflections.
  • 6. Surface Currents
  • 7. Surface Currents
  • 8. Surface Currents Winds that blow across the Earth’s surface create surface currents in the ocean. Different winds cause currents to flow in different directions.
  • 9. Think/Pair/Share Winds are responsible for currents. What is responsible for wind?
  • 10. Surface Currents Who can draw a straight line? The Coriolis Effect is the apparent curving of moving objects from a straight path due to the Earth’s rotation.
  • 11. Coriolis Effect Does the Coriolis Effect affect which way water goes down a drain?
  • 12. Surface Currents When surface currents meet continents, the currents deflect, or change direction.
  • 13. Surface Currents Currents are also affected by the temperature of the water in which they form. On maps, warm-water currents are often shown as red arrows, and cold-water currents are shown as blue arrows.
  • 14. Deep Currents Stream-like movements of ocean water located far below the surface are called deep currents. Deep currents are not controlled by wind. Deep currents form in parts of the ocean where water density increases. The density of the ocean is affected by temperature and salinity.
  • 15. Deep Currents Differences in water density cause variations in the movement of deep currents.
  • 16. Section 1 Review p.85 #2-8
  • 17. Warmup Given the average yearly temperatures for the Scilly Isles in England and Newfoundland in Canada, can you explain why the two locations have very different yearround temperatures? Note their locations on the globe, and use what you know about the movement of ocean currents to support your answer.
  • 18. Section 2: Currents & Climate By the end of this section, you should be able to: Explain how currents affect climate. Describe the effects of El Niño. Explain how scientists study and predict the pattern of El Niño.
  • 19. Graphing Temperatures Pair up with a partner. Select 2 pairs of cities on opposites sides of a continent. They should all be at approximately the same latitude. One city from each pair should be on the coast, the other should be less than 200 miles inland. Find the average high and low temperatures for each city. Find the average ocean temperature for the coastal cities. Display the information on a bar graph. Explain how ocean temperature affects the climate of coastal cities.
  • 20. Surface Currents & Climate Warm-water currents create warmer climates in coastal areas that would otherwise be much cooler.
  • 21. Surface Currents & Climate Cold-water currents keep climates along a coast cooler than the inland climate year-round.
  • 22. Surface Currents & Climate Upwelling is the movement of deep, cold, and nutrient-rich water to the surface of the ocean.
  • 23. Surface Currents & Climate The nutrients that are brought to the surface support the growth of plankton. Plankton support larger organisms, such as fish and seabirds.
  • 24. Surface Currents & Climate El Niño is a change in the water temperature in the Pacific Ocean that produces a warm current. El Niño alters weather patterns enough to cause disasters, including flash floods, mudslides, and droughts.
  • 25. Surface Currents & Climate El Niño also prevents upwelling off the coast of South America. Learning as much as possible about El Niño is important because of its effects on organisms and land. To study El Niño, scientist use a network of buoys located along the equator. The buoys collect data about surface temperature, air temperature, currents, and wind.
  • 26. Section 2 Review p.89 #2-6
  • 27. Warmup Imagine you are floating in the ocean 1 km from shore, which is north of you. There is a surface current flowing east. Are you more likely to travel north with the waves toward the shore or east with the surface current?
  • 28. Section 3: Waves By the end of this section, you should be able to: Identify the parts of a wave. Explain how the parts of a wave relate to wave movement. Describe how ocean waves form and move. Classify types of waves.
  • 29. Anatomy of a Wave Waves are made up of crests and troughs. A crest is the highest point of a wave. A trough is the lowest point of a wave.
  • 30. Wave Formation & Movement Most waves form as wind blows across the water’s surface and transfers energy to the water. As the energy moves through the water, so do the waves. But the water itself stays behind, rising and falling in circular movements.
  • 31. Wave Formation & Movement
  • 32. Wave Formation & Movement Wave period is the time between the passage of two wave crests (or troughs) at a fixed point.
  • 33. Types of Waves Deep-water waves are waves that move in water deeper than one-half their wavelength. When deep-water waves begin to interact with the ocean floor, the waves are called shallow-water waves.
  • 34. Types of Waves When waves crash on the beach head-on, the water they moved through flows back to the ocean underneath new incoming waves. This movement of water forms a subsurface current that pulls objects out to sea and is called an undertow.
  • 35. Types of Waves Longshore currents are water currents that travel near and parallel to the shore line. They form when waves hit the shore at an angle. Longshore currents transport most of the sediment in beach environments
  • 36. Types of Waves Sometimes waves called whitecaps and swells form in the open ocean. White, foaming waves with very steep crests that break in the open ocean before the waves get close to the shore are called whitecaps. Rolling waves that move steadily across the ocean are called swells.
  • 37. Which is which?
  • 38. Types of Waves Tsunamis are waves that form when a large volume of ocean water is suddenly moved up or down. This movement can be caused by underwater earthquakes.
  • 39. Types of Waves Storm Surges are local rises in sea level near the shore that are caused by strong winds from a storm. Winds form a storm surge by blowing water into a big pile under the storm. As the storm moves onto shore, so does the giant mass of water beneath it.
  • 40. Section 3 Review p.95 #4-13
  • 41. Warmup If the moon had the mass of a golf ball, the sun would have the mass of about 110 school buses! This analogy shows the difference in mass of the moon and the sun. Although the moon is much smaller than the sun is, the moon exerts more influence on Earth’s tides than the sun does. Why do you think this happens?
  • 42. Section 4: Tides By the end of this section, you should be able to: Explain tides and their relationship with the Earth, sun, and moon. Describe four different types of tides. Analyze the relationship between tides and coastal land.
  • 43. The Lure of the Moon The daily changes in the level of ocean water are called tides. Tides are influenced by the sun and the moon and occur in a variety of cycles. How often tides occur and the difference in tidal levels depend on the position of the moon as it revolves around the Earth.
  • 44. The Lure of the Moon When part of the ocean is directly facing the moon, the water there and the water on the opposite side of Earth bulges toward the moon. The bulges are called high tides. Water is drawn away from the areas between the high tides, which causes low tides to form.
  • 45. The Lure of the Moon Tides occur at different times each day because the Earth rotates more quickly than the moon revolves around the Earth.
  • 46. Tidal Variations The sun also affects tides. The combined forces of the sun and the moon on Earth result in tidal ranges that vary based on the positions of the three bodies. A tidal range is the difference between levels of ocean water at high tide and low tide.
  • 47. Tidal Variations Spring Tides are tides with the largest daily tidal range and occur during new and full moons. During these times, the sun, Earth, and moon are aligned. Neap Tides are tides with the smallest daily tidal range and occur during the first and third quarters of the moon. During these times, the sun, Earth and moon form a 90º angle.
  • 48. Tides and Topography In some coastal areas that have narrow inlets, movements of water called tidal bores occur. A tidal bore is a body of water that rushes up through a narrow bay, estuary, or river channel during the rise of high tide and causes a very sudden tidal rise.
  • 49. Section 4 Review p.99 #2-7