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 2,500 km, the distance after 100 million years
   • About 25 km, since 2.5 million cm is 25 km
   • About 2,500,000 km, the number of centimeters written as kilometers
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?

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

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

   • 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
   • 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
5. 4.

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

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

   Card C: temperature falls 6.5 degrees per 1,000 m. About how many degrees colder is the Kilimanjaro summit than sea level, Luz asks?

   • About 28 degrees colder, the sea-level temperature itself
   • About 38 degrees colder, since 5.9 times 6.5 is about 38
   • About 5,895 degrees colder, using the height as the drop
   • About 6 degrees colder, using just one step of 1,000 m
7. 6.

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

   • About -10 degrees Celsius, since 28 minus 38 is -10
   • About 66 degrees Celsius, since 28 plus 38 is 66
   • About 22 degrees Celsius, since one 6.5-degree step is taken from 28
   • About 38 degrees Celsius, the drop in temperature itself
8. 7.

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

   • 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
   • Strong: card C gives a sea-level temperature of 28 degrees, so the top is warm too
   • Weak: height cools the air by about 38 degrees, enough to freeze at the top
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 one seventh, so the Amazon is the gentler river of the two
   • About 7 times as steep, since 0.87 divided by 0.12 is about 7
   • 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
    • Another book that repeats one of the lengths in clear print
    • An agreed starting point and one method used the same way on each river
    • 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 speed varies by place and over time, so one number is only a guide
    • Plates moved faster long ago, so today's average is not worth using
    • The measurement is unreliable, so the plates may not be moving at all
    • The plates move exactly 2.5 cm each year in every place without change