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1. What are ocean currents and how are they formed?
Ans. Ocean currents are movements of sea water caused by wind and theEarth's rotation, among other factors.
2. What are trade winds?
Ans. As the Earth spins from west to east (or left to right), the highand low pressure air cells move. These moving air cells are called tradewinds and blow in one prevailing direction, depending on their latitude(Figure 121.3). The factors which determine wind direction were discussedin Chapter 7.
3. What is the Walker circulation? Draw a diagram to illustrate youranswer.
Ans. The Walker circulation is the name given to the way that trade windscirculate air to and fro across the Pacific Ocean.
4. How is the Southern Oscillation Index calculated ?
Ans. From the pressure difference between Tahiti and Darwin.
5. Where is the El Niño current found?
Ans. Off the coast of Peru.
6. Draw a diagram to show how the El Niño current can effect thePeruvian fishing industry.
Ans. See Figure 124.1.
7. How does El Niño event affect cyclones?
Ans. In El Niño events, ocean temperatures can drop, changingcyclone paths so that cyclones have been recorded as far south as northernNew South Wales.
8. Name any four ocean currents found around Australia or New Zealand.
Ans. Eastern Australaian, Western Australian, Leeuwin, Flinders, Tasman,Westland, Southland, East Auckland and East Cape currents.
9. What are eddies?
Ans. Large circulating bodies of water formed off Eastern Australia.
10. What is the main current that influences coasts of Western Australia?
11. How can tidal currents form?
Ans. As a result of the rise and fall of tides along the coastline andin estuaries.
12. In the article from CSIRO, what could have happend to the crew ofthe Blythe Star if their ship had gone down a month later?
Ans. They would have been causght up in the Antarctic current.
13. What type of currents form in river mouths that have been constrainedby training walls?
Ans. Tidal and river currents.
14. What is an overflow current and how can it form?
Ans. A current that passes over submerged rocks. it can form when windblows over the tide.
15. What is a longshore current and how is it formed?
Ans. If waves approach a beach at an angle, as shown in Figure 129.3,they set up a longshore current close to the beach.
16. Draw a fully labelled diagram of a rip current that forms on a beach.
Ans. See Figure 130.1.
17. If you are caught in a rip current, what should you do?
Ans. If caught in a rip, all you have to do is to stay calm, dive underthe waves as you are taken out to sea, and attract help when you are pastthe breakers. Alternatively, swim sideways till you reach a sandbank andthen catch the next wave in further up or down the beach.
18. Name four types of rip that can occur on surfing beaches.
· permanent where the current remains in the same place for months,even years;
·fixed where a gutter or depression in beach sand keeps a ripin place for months;
· flash rips where a depression suddenly occurs in a beach profile;and
· travelling where a rip moves up the coast.
1. Look up the CSIRO Marine Laboratories address in Hobart then writefor a list of brochures on oceanography. Read them.
In 1997 the address was: GPO Box 1538 Hobart and their web address was:
2. Prepare a chart of the local currents in your area. Write an essayon how they effect local industries.
Talk to rescue associations or local fishers.
3. Find Tahiti on a map. Why were the South Pacific islands so concernedabout French nuclear testing?
Use your library and a good atlas.
4. Research the trade winds and find out how they played an importantpart in your local maritime history.
Use your library.
5. Prepare a summary poster on El Niño using the colour diagramsin this Chapter.
Use colouring in pencils and the chapter illustrations. Don't forgetto acknowledge the hard work of use all here at Wet Paper!!
5. Write to your local weather bureau and find how the Southern OscillationIndex (SOI) affects your area.
Use the phone book.
6. Read Thor Heyedahls book - Ra II.
Visit your library.
6. El Niño
9. Southern Oscillation
14. longshore current