to Videolink arrow

Newton logo to print

Equator

 

Overview

Run your finger along the equator on a globe. What do you see in your mind's eye as your finger passes over continents and oceans? Tropical rain forests? Houses on stilts? Blazing temperatures? Stop your finger on the east African country of Kenya and be prepared for new impressions. Lying on the equator in the southwestern corner of Kenya is the Maasai Mara National Reserve - a nature preserve that defies the usual image of the equatorial tropics. This reserve is a part of the Serengeti-Mara ecosystem. Here you will find not rain forests, but woodlands and savanna. Two million years ago, volcanic and tectonic activity pushed up the lush forest floors of this region, creating a plateau 1,520 meters (5,000 feet) above sea level. At this elevation, the warm ocean winds were cut off, forests disappeared, and volcanic ash settled over the highlands, creating the rolling plains of today. Temperatures can reach 38 C (100 F) and cool to 10 C (50 F). Dramatic volcanic action also produced Mount Kenya. Once higher than Mount Everest, Mount Kenya now stands 5,200 meters (17,000 feet) high and is crowned with snow. Snow! On the equator? Why doesn't the snow melt? First, as one ascends from sea level, the temperature decreases. In fact, according to the adiabatic lapse rate, for every thousand feet, the temperature drops approximately 3.1 C (5.5 F). Second, the shiny surface of the snow reflects the sun's rays, keeping the snow frozen. (This effect is called the albedo.) Third, the snow is so densely packed at the peak that the lower layers of snow cool the surface layer, counteracting the warming effects of the sun. Life in the shadow of Mount Kenya may defy our equatorial image, too. For a thousand years, the nomadic Maasai have shared their home with wildebeest, lion, and giraffe. More precious to the Maasai are the herds of cattle upon which their livelihood, wealth, and prestige depend. The Maasai villages are built with the materials at hand-mud, cow dung, and sticks. Women are responsible for the construction of the family boma. Life in the manyatta follows traditional patterns, and the roles of its members are clearly defined. Boys take care of the cattle, girls help their mothers, and elders enjoy their honored roles as village leaders. Although life in nearby cities offers modern conveniences, many Maasai prefer the path of their ancestors under the direct rays of the equatorial sun.

Activity

Make your own sextant and find out how far you are from the equator. Explorers of old could determine their location in the Northern Hemisphere by using a sextant and sighting the North Star. From these, they could calculate their latitude. Follow these directions to make a simple sextant. Calculate your latitude to find out how far north you are from the equator. Materials
  • one 15 cm x 15 cm (6" x 6") piece of poster board
  • one plastic drinking straw
  • small weight such as metal sinker or washer
  • paper clip
  • transparent tape
  • protractor
  • pencil
  • scissors
1. Draw two lines, each 1.25 cm (1/2") from the edge of the poster board, so that the lines make a right angle at the corner of the board. 2. With your protractor as a guide, draw an arc between the two lines. 3. Using the protractor, mark off every five degrees from 0 to 90 and label each mark. Trim off the extra poster board along the arc. 4. Make a hole at the right angle as shown and thread the piece of string through it. At one end, tie a paper clip so that the string doesn't slip through the hole. Tie the weight to the other end so that it hangs straight down. 5. Tape the straw to the edge of the poster board closest to the 90 degree mark. 6. On a clear night, go outside and find the constellation Ursa Major (also known as the Big Dipper). Using your sextant, sight the North Star through the straw. Notice you are actually measuring the angle from the horizon to the North Star. Write down the degree of the angle as marked by the string on the sextant. This shows your latitude from the equator. Check your answer using a map or globe. Questions 1. One degree latitude is approximately 110 km (69 miles). How far are you from the equator? 2. Why is it possible to calculate the latitude by sighting the North Star?

Resources

  • Dinesen, I. (1985) Out of Africa. New York: Vintage Books. (First published in
    1937.)
  • Eyewitness visual dictionary of the earth. (1993) London: Dorling Kindersley.
  • Farndon, J. (1994) The dictionary of the earth. London: Dorling Kindersley.
  • Jobb, J. (1977) The night sky book. Boston: Little, Brown and Company.
  • Krupp, E.C. (1989) The big dipper and you. New York: Morrow Junior Books.
  • Stott, C. (1993) Eyewitness explorers: Night sky. London: Dorling Kindersley.
  • Wood, R.W. (1992) Science for kids: 39 easy geography activities. Blue Ridge
    Summit, PA: Tab Books.
    Additional resources

    1. National Geographic: Africa's animal oasis; Africa: Physical geography of the
      continents; and Serengeti diary. Videotapes. (800) 368-2728.
    2. Tom Snyder Productions: Mapping the world by heart. Curriculum kit. (800)
      342-0236.
      *