How fast plates move

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Card (USGS)

   1 cm a year is 10 km per million years.

2. 1.

   A plate moves 4 cm a year. How far does it move in 1 million years, by Ari's math?

   • 40 km
   • 400 km
   • 4,000 km
   • 4 km
3. 2.

   A plate moves 100 km in 1 million years. What is that in cm a year, by Bo's math?

   • 1 cm a year
   • 100 cm a year
   • 0.1 cm a year
   • 10 cm a year
4. 3.

   Midway is about 28 million years old and lies about 2,600 km from the Big Island. Midway is 28 million years old and about 2,600 km from the Big Island. What is the rate in km per million years, by Kira's math?

   • About 7,280 km per million years
   • About 9.3 km per million years
   • About 93 km per million years
   • About 0.011 km per million years
5. 4.

   The stripe is 200 km from the ridge and 8 million years old. A dated stripe lies 200 km from a ridge and is 8 million years old (example). What is the spreading rate, by Jun's math? (1 km = 100,000 cm.)

   • 40 cm a year
   • 0.25 cm a year
   • 25 cm a year
   • 2.5 cm a year
6. 5.

   The offset is 150 km and took 3 million years. USGS: the San Andreas slips about 5 cm a year. A rock formation is offset 150 km along a fault in 3 million years (example). What is the slip rate, by Luz's math?

   • 50 cm a year
   • 5 cm a year
   • 0.5 cm a year
   • 450 cm a year
7. 6.

   Ages increase to the west-northwest along the chain. Kauai is about 5 million years old and Midway about 28 million. Island ages rise toward the west-northwest. Which way has the plate carried the islands from the hotspot, by Noah's reading?

   • It stayed put, because the islands formed in place
   • Toward the south, since the Big Island is the youngest
   • Toward the west-northwest, where the older islands lie
   • Toward the east-southeast, where the younger islands lie

8. Card (USGS)

   The Big Island is under 0.7 million years old, Kauai about 5 million, Midway about 28 million, and the northernmost seamounts about 80 million.

9. 7.

   Which list runs from youngest to oldest, by Ren's reading?

   • Big Island, Midway, Kauai, northernmost seamounts
   • Kauai, Big Island, Midway, northernmost seamounts
   • Big Island, Kauai, Midway, northernmost seamounts
   • Northernmost seamounts, Midway, Kauai, Big Island
10. 8.

    The Mid-Atlantic Ridge spreads about 2.5 cm a year. The East Pacific Rise spreads over 15 cm a year. At least how many times faster is the East Pacific Rise than the Mid-Atlantic Ridge, by Tala's math?

    • More than 12.5 times
    • More than 6 times
    • More than 37 times
    • About 0.17 times, one-sixth as fast
11. 9.

    GPS and space geodesy measure movement now. Dated sea-floor stripes, dated volcanoes and offset rock formations give long-term rates. Which method gives the plate's rate for today, and which gives a long-term rate, by Zee's reading?

    • Dated stripes give both, because they were laid down yesterday
    • GPS gives both, because it measures stripes
    • Dated stripes give today's rate; GPS gives a long-term rate
    • GPS gives today's rate; dated stripes give a long-term rate

12. Card (USGS)

    The Pacific Plate moves about 6 cm a year today. Midway's age gives about 9.3 cm a year over 28 million years.

13. 10.

    The Pacific Plate is said to move 6 cm a year and also 9.3 cm a year. Which statement explains this, by Esme's reading?

    • Both are today's rates, measured by two different GPS stations
    • Both are long-term rates, and one of them has a printing error
    • One must be wrong, since a plate has a single fixed speed
    • They are different spans: 6 is today's rate and 9.3 is an average over 28 million years