Continents, oceans, great rivers, mountains and deserts

Grade 6 Social Studies Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Dry lands and map scale (cards A to D; areas are rounded). Card A, four deserts: Sahara (Africa, hot) | 9.2 million km2. Antarctica (polar, cold) | 14.2 million km2. Gobi (Asia, cold winters) | 1.3 million km2. Atacama (South America, along the Pacific coast) | 105,000 km2. A desert is a place that gets less than 250 mm of rain or snow in a year, whether it is hot or cold. Card B, yearly rainfall averages over many years: Manaus, Brazil, about 2,300 mm; Arica, Chile, in the Atacama, about 1 mm. Card C, causes: the Atacama is dry because cold water offshore cools the air and the Andes block moist air from the east. The Gobi lies far from the oceans and in the rain shadow of mountains such as the Himalayas. Antarctica's air is so cold that it holds little moisture, so little snow falls. Card D, a practice map (invented): the scale is 1 cm = 500 km. On the map, Town X and Town Y are 3.6 cm apart, and Mountain range M is 4.8 cm long.

2. 1.

   Mountain range M is 4.8 cm long on card D. How long is it in real life, Bo asks?

   • About 104 km, found by dividing 500 by 4.8
   • 2,400 m, the same digits in a smaller unit
   • 500 km, the number of kilometers in one centimeter
   • 2,400 km, since 4.8 times 500 km is 2,400 km
3. 2.

   Two cities are 1,750 km apart. How far apart will they be on card D's map, Esme asks?

   • 875,000 cm, found by multiplying 1,750 by 500
   • 500 cm, the number from the scale
   • 3.5 cm, since 1,750 divided by 500 is 3.5
   • 35 cm, since 1,750 divided by 50 is 35
4. 3.

   Using card A, about how many times as large as the Gobi is the Sahara, Jun asks?

   • About 7 times, since 9.2 divided by 1.3 is about 7
   • About 7.9 times, since 9.2 minus 1.3 is 7.9
   • About 70 times, since 92 divided by 1.3 is about 70
   • About 11 times, comparing Antarctica's 14.2 with the Gobi's 1.3
5. 4.

   A student says, "A desert is always hot." How does card A answer, Kira asks?

   • Weak: Antarctica gets more than 250 mm, so card A does not call it a desert
   • Strong: the Sahara is the largest hot desert, so heat is what makes a desert
   • Weak: card A is a table of areas, so it cannot say anything about heat
   • Weak: a desert is defined by little precipitation, so cold Antarctica counts
6. 5.

   Using card C, which chain explains the Atacama's dryness, Luz asks?

   • Warm offshore water fills the air with moisture, and the Andes carry it to the coast
   • The Atacama is far from any ocean, so moist air cannot reach it
   • Sand soaks up the rain after it falls, which leaves the surface dry
   • Cold offshore water and the Andes block moist air, so little rain reaches the coast
7. 6.

   Why can a very cold place such as Antarctica be a desert, as card C suggests, Milo asks?

   • Cold air holds a lot of moisture, but the ice stops snow from falling
   • Deserts are defined by sand, and ice counts as a kind of sand
   • Very cold air holds little moisture, so little snow falls, even though ice stays
   • Antarctica is too far from the equator for rain or snow to fall anywhere, so it is a desert
8. 7.

   Card B: Manaus gets about 2,300 mm and card A's desert limit is 250 mm. About how many times the limit is that, Pia asks?

   • About 9 times, since 2,300 divided by 250 is about 9
   • About one ninth, since the limit is the smaller of the two numbers
   • About 90 times, since 2,300 divided by 25 is about 90
   • About 2,050 times, since 2,300 minus 250 is 2,050
9. 8.

   A student says, "The Sahara is the world's largest desert." How does card A answer, Ren asks?

   • Weak: card A gives areas that are rounded, so it cannot compare deserts
   • Strong: card A lists the Sahara first, so it must be the largest
   • Weak: Antarctica, at 14.2 million km2, is larger than the Sahara
   • Strong: deserts are hot places, so Antarctica is not counted
10. 9.

    Card B uses averages over many years. Why not use one year's rainfall, Tala asks?

    • Rainfall is the same in each year, so more years add nothing new to the answer
    • One year may be unusually wet or dry; many years show the typical amount
    • A single year is a later report, so it cannot be trusted
    • Averages are exact, so they fix the rainfall of each year
11. 10.

    Suppose another book gives the Sahara as 8.6 million km2, but card A says 9.2. Why might sources differ, Zee asks?

    • One book must have a typing error, so it can be set aside without checking
    • Older books measure in miles and newer ones in kilometers, so the digits differ
    • They may draw the desert's edge in different places or use newer measurements
    • The Sahara changes its area with each sandstorm, so any number is wrong