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Notes Points

Notes Points. Name __________________________________ Period _______. Chapter 21 Standard.

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Notes Points

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  1. Notes Points Name __________________________________ Period _______

  2. Chapter 21 Standard 5d. Students know properties of ocean water, such as temperature and salinity, can be used to explain the layered structure of the oceans, the generation of horizontal and vertical ocean currents, and the geographic distribution of marine organisms.

  3. Chapter 21 Movements of the Oceans

  4. I. 21.1 Ocean Currents

  5. Ocean currents are complex. • The water in the ocean moves in giant, horizontal streams called currents. • Ocean currents are identified by: • physical and chemical properties • path of debris left by ships • Two main categories of ocean currents: • surface currents • deep currents

  6. There are factors that affect surface currents. • Surface currents are currents that move on or near the surface of the ocean and are driven by winds. • Surface currents are controlled by three factors: • air currents (wind) • Earth’s rotation • location of the continents

  7. Surface Currents and Air Currents (Winds) • All surface currents are affected by air currents (winds). • As wind moves, it stores energy. • As wind moves across the ocean’s surface, the wind passes this energy onto the ocean. • As the energy is transferred, the water at the ocean’s surface begins to move. • Global wind belts (trade winds, westerlies and polar easterlies) blow in different directions. • Based on the direction of the wind, the ocean waters will also move in the same direction.

  8. Surface Currents and Earth’s Rotation • Global wind belts and ocean currents do not flow in straight lines. • Both wind belts and ocean currents follow a curved path because of the Earth’s rotation. • The curving of the path of oceans and winds due to Earth’s rotation is called the Coriolis Effect.

  9. Wind patterns caused by Coriolis Effect are given certain names (trade winds, easterlies, westerlies). Ocean patterns are given the name gyres. • Gyres are huge circles of moving water caused by wind belts and the CoriolisEffect. • In the Northern Hemisphere, water flow in gyres is to the right, or clockwise. • In the Southern Hemisphere, water flow in gyres is to the left, or counter clockwise.

  10. (Color and label the picture.) Deflection and division of surface currents caused by continents. • Surface Currents and Continental Barriers • The continents are another major influence on surface currents because they act as barriers to surface currents. • When a surface current flows against a continent, the current is deflected and divided.

  11. Major Surface Currents • Surface currents are found all over the world. • There are three major surface current regions: • the equatorial region • the Southern Hemisphere • the Northern Hemisphere

  12. Major Surface Currents of the Oceans of the World

  13. Major Surface Currents of the Equatorial Region • Equatorial currents are found at the EQUATOR! • Warm equatorial currents are located in the Atlantic, Pacific, and Indian Oceans. • Each of these oceans has two warm-water currents that move in a westward direction. • Between these two westward flowing currents lies a weaker, eastward flowing current called the Equatorial Countercurrent.

  14. Major Surface Currents of the Southern Hemisphere • In the Southern Hemisphere, the currents in gyres move counterclockwise. • The world’s largest current is found in the Antarctic, Pacific, and Atlantic Oceans and it is called the Antarctic Circumpolar Current. • The Indian Ocean surface currents follow two patterns. • In the Southern Indian Ocean, currents follow a circular, counterclockwise gyre. • In the Northern Indian Ocean, currents are governed by monsoons which are winds that change directions seasonally.

  15. Major Surface Currents of the Northern Hemisphere (North Atlantic or North Pacific) • Currents in North Atlantic – all currents make a huge gyre known as the North Atlantic Gyre. It contains: • Gulf Stream – a swift, warm current • Labrador Current – a cold current • North Atlantic Current – a warm current which splits to form: • Norway Current • Canary Current

  16. Currents in the North Pacific – all currents also make a huge gyre. It contains: • Kurishio Current – a warm current • North Pacific Drift • California Current – a cool current

  17. (Color and the picture.) North Atlantic Gyre

  18. Deep Currents vs. Surface Currents • Deep currents are found deeper in the ocean than surface currents. • Deep currents are not driven by the wind like surface currents are. • Deep currents move much more slowly than surface currents.

  19. Deep Current Movement • As learned before, two factors affect density of ocean water: temperature and salinity. • The movement of polar waters is a result of cold, dense water sinking and warm, less dense water rising (remember convection?!). • The water in polar regions has high salinity so it will sink when it comes into contact with less salty waters, again causing movement. • Deep currents form as cold, dense water of the polar regions sinks and flows beneath warmer water.

  20. Deep Currents of the Antarctic Bottom • The waters off the coast of the Antarctica are the densest and coldest because it has high salinity and the temperature is -2oC. • This forms deep current: the Antarctic Bottom Water which moves slowly northward.

  21. Deep Currents and Turbidity Currents • A turbidity current is a strong current caused by an underwater landslide. • These landslides occur when sediment under water becomes loose and break apart causing debris and dirt into the water which makes it cloudy or turbid. • Turbid water is more dense than clear water, so turbid water will sink below the clear water. This results in movement.

  22. Write 10 questions for this section. • Highlight key words and phrases. • Draw a picture.

  23. Summary (one paragraph) – Page 4 Currents are ___________________________________. The two types of currents are __________ and __________ currents. Surface currents are controlled by three factors: ______________, _____________ and _______________. Gyres are ____________________. Deep currents are found _____________ than surface currents. A turbidity current is _____________________.

  24. II. 21.2 Ocean Waves

  25. Waves • Wave is a periodic disturbance in a solid, liquid, or gas as energy travels through it. • Ocean water waves are described as having a periodic up-and-down movement. • Ocean waves result from the transfer of energy from wind to water.

  26. Wave Parts • A wave has several main parts: • Crest – highest point of a wave • Trough – lowest point of a wave • Wave Height – the vertical distance between the crest and the trough • Wavelength – the horizontal distance between two consecutive crests or between two consecutive troughs • Wave Period – the time required for two consecutive wave crests to pass a given point

  27. (Color and label the picture.) A B wave height still water level Wave Period: Time required for wave crest at point A to reach point B

  28. Wave Energy • Uneven heating of Earth’s atmosphere causes wind. • Wind then transfers energy to oceans to form small waves, or ripples. • As a ripple receives more energy, the ripples grow into a larger wave. • The more energy (wind) = the greater the wave

  29. Water Movement in a Wave • Water particles move in a circular motion. • During a single wave period, each water particle moves in one complete circle. • When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward. • The energy of a wave moves from water molecule to water molecule but as a whole, water itself moves very little.

  30. Wave Size • Determined by three factors • Speed of wind • Length of time wind blows • Fetch – distance that the wind can blow across open water

  31. During a great storm, steady high winds can cause waves to reach great size.

  32. On calm days, smooth waves move across the surface. • Swells are a group of long, rolling waves that are of similar size. • When winds blow off the crest of a wave, white caps form.

  33. Waves and the Coastline • Breakers • Near the coastline where it is shallow, the bottom of a wave touches the ocean floor which creates friction. • Friction will cause the bottom of the wave to slow down while the top of the wave will continue to move forward. • The top of the water topples forward and results in a breaker which is a foamy mass of water that washes onto the coastline.

  34. Refraction • Most waves approach the coastline at an angle. • Refraction is the process by which ocean waves bend toward the coastline.

  35. Undertows and Rip Currents • Water carried onto a beach by breaking waves is pulled back into deep water by gravity. This results in an irregular current called an undertow. • Rip currents form when water from large breakers returns to the ocean through channels parallel to the beach.

  36. Longshore currents • Longshore currents form when waves approach the beach at an angle. • They flow parallel to the shore. • Sandbars form when deposited sand from waves form low ridges.

  37. Tsunamis • Sometimes called tidal waves even though they are not caused by tides. • Tsunamis are giant seismic waves. They are caused by: • Earthquakes on ocean floor • Volcanic eruptions • Underwater landslides

  38. Characteristics of Tsunamis include: • Have a long wavelength • Have a tremendous amount of energy • Height can reach 30 to 40 m

  39. Write 10 questions for this section. • You should have a total of 20 questions. • Highlight key words and phrases. • Draw a picture. J. Nguyen – Physical Science

  40. Summary (one paragraph) – Page 6 Wave is ______________________________________. Wave size is determined by three factors: ____________, _____________ and _____________. The crest is the ______________ point while the trough is the ______________ point. Swells are _________________. A breaker is ___________________________________. Tsunamis are ______________________________. J. Nguyen – Physical Science

  41. Notes Points Name __________________________________ Period _______ J. Nguyen – Physical Science

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