Continents, oceans, great rivers, mountains and deserts

Grade 6 Social Studies Worksheet

Circle the best answer.

1. Read this first

   Use this

   What shapes the land (cards A to D; invented places are marked). Card A, plates: at the Mid-Atlantic Ridge the North American and Eurasian plates move apart at about 2.5 cm per year, a rough average, and Iceland sits on the ridge. The Himalayas rose where the Indian plate pushes into the Eurasian plate. Card B, an invented mountain: moist air blows in from the west. Westport, on the west side of Mount Alder, gets about 2,400 mm of rain a year. Eastdale, on the east side, gets about 300 mm. Moist air rises on the windward side, cools and drops rain; air sinking on the leeward side is dry. Card C, height and temperature: average air temperature falls about 6.5 degrees Celsius for every 1,000 m of height. Suppose it is 28 degrees Celsius at sea level near Mount Kilimanjaro, which is about 3 degrees south of the equator and 5,895 m high. Card D, two rivers (lengths differ by source): the Mississippi starts at Lake Itasca, about 450 m above sea level, and runs about 3,700 km to the sea. The Amazon starts high in the Andes, near Nevado Mismi at about 5,600 m, and runs about 6,400 km to the sea.

2. 1.

   Card A: plates move apart 2.5 cm per year. If the rate stayed the same, how far apart after 1 million years, Ari asks?

   • About 250 km, since 2.5 million cm divided by 10,000 is 250
   • About 25 km, since 2.5 million cm is 25 km
   • About 2,500,000 km, the number of centimeters written as kilometers
   • About 2,500 km, the distance after 100 million years
3. 2.

   Card B: Westport gets about 2,400 mm of rain and Eastdale about 300 mm. About how many times as much rain falls at Westport, Bo asks?

   • 2,100 times as much, since 2,400 minus 300 is 2,100
   • 80 times as much, since 2,400 divided by 30 is 80
   • 8 times as much, since 2,400 divided by 300 is 8
   • 8 times as much at Eastdale, since it is on the other side
4. 3.

   Using card B, which chain explains Eastdale's low rainfall, Esme asks?

   • Eastdale is far from the ocean, so no air reaches it
   • Moist air drops its rain on the west side, so the air reaching the east is dry
   • Rain falls equally on both sides, but evaporates faster at Eastdale
   • Dry air rises on the west side and falls as rain on the east side of the mountain
5. 4.

   Card A says the Indian plate pushes into the Eurasian plate. What follows, as the card suggests, Kira asks?

   • Mountains rose first and then pushed the plates together over time
   • The plates move apart, so Iceland rises between them
   • Rock is squeezed upward, so a range such as the Himalayas rises
   • Rock is pulled apart, so a deep ocean ridge forms where the plates meet
6. 5.

   Using card C, about what is the air temperature at the Kilimanjaro summit, Milo asks?

   • About 38 degrees Celsius, the drop in temperature itself
   • About -10 degrees Celsius, since 28 minus 38 is -10
   • About 22 degrees Celsius, since one 6.5-degree step is taken from 28
   • About 66 degrees Celsius, since 28 plus 38 is 66
7. 6.

   A student says, "Kilimanjaro is close to the equator, so its top cannot be icy." How does card C answer, Noah asks?

   • Strong: card C gives a sea-level temperature of 28 degrees, so the top is warm too
   • Strong: places near the equator stay warm at any height, so ice cannot form
   • Weak: card C is about supposed numbers, so it cannot test the claim
   • Weak: height cools the air by about 38 degrees, enough to freeze at the top
8. 7.

   Card D: about how much does the Mississippi drop for each kilometer on average, Pia asks?

   • About 1.2 m per km, since 450 divided by 370 is about 1.2
   • About 0.12 m per km, since 450 over 3,700 is about 0.12
   • About 450 m per km, the height of the river's source
   • About 8 m per km, since 3,700 divided by 450 is about 8
9. 8.

   Using card D, about how many times as steep, on average, is the Amazon as the Mississippi, Ren asks?

   • About 0.75 times, since the Amazon's 0.87 m per km minus 0.12 is 0.75
   • About 7 times as steep, since 0.87 divided by 0.12 is about 7
   • About one seventh, so the Amazon is the gentler river of the two
   • About 70 times, since 0.87 divided by 0.012 is about 70
10. 9.

    Card D says river lengths differ by source. What would best help settle the Amazon's length, Tala asks?

    • A map showing the river's height where it reaches the sea
    • An agreed starting point and one method used the same way on each river
    • Another book that repeats one of the lengths in clear print
    • Nothing, because rivers change too much for any length to be measured fairly
11. 10.

    Card A calls 2.5 cm per year "a rough average." Why does the card say that, Zee asks?

    • The plates move exactly 2.5 cm each year in every place without change
    • The speed varies by place and over time, so one number is only a guide
    • The measurement is unreliable, so the plates may not be moving at all
    • Plates moved faster long ago, so today's average is not worth using