How fast plates move

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   1 cm a year is 10 km per million years. A plate moves 100 km in 1 million years. What is that in cm a year, by Bo's math?

   • 0.1 cm a year
   • 10 cm a year
   • 100 cm a year
   • 1 cm a year
2. 2.

   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 93 km per million years
   • About 9.3 km per million years
   • About 0.011 km per million years
   • About 7,280 km per million years
3. 3.

   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.)

   • 0.25 cm a year
   • 40 cm a year
   • 2.5 cm a year
   • 25 cm a year
4. 4.

   India moved about 9 m a century. 1 m is 100 cm. USGS says India moved about 9 m a century. What is that in cm a year, by Milo's math?

   • 9 cm a year
   • 90 cm a year
   • 0.9 cm a year
   • 9 m a year
5. 5.

   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 west-northwest, where the older islands lie
   • Toward the south, since the Big Island is the youngest
   • Toward the east-southeast, where the younger islands lie

6. Read this first

   Card (USGS)

   The Big Island's rocks are under 0.7 million years old. Kauai's oldest rocks are about 5.5 million years old. Midway is about 28 million.

7. 6.

   Which island is over the hotspot now, by Pia's reading of the ages?

   • Midway, with rocks about 28 million years old
   • The northernmost seamounts, the oldest in the chain
   • Kauai, with rocks about 5.5 million years old
   • The Big Island, with the youngest rocks

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?

   • Northernmost seamounts, Midway, Kauai, Big Island
   • Big Island, Kauai, Midway, northernmost seamounts
   • Big Island, Midway, Kauai, northernmost seamounts
   • Kauai, Big Island, Midway, northernmost seamounts
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 6 times
    • More than 37 times
    • About 0.17 times, one-sixth as fast
    • More than 12.5 times
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?

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

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 long-term rates, and one of them has a printing error
    • Both are today's rates, measured by two different GPS stations
    • 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