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?

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

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

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

   • 40 cm a year
   • 2.5 cm a year
   • 0.25 cm a year
   • 25 cm a year
5. 4.

   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
6. 5.

   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?

   • 0.9 cm a year
   • 90 cm a year
   • 9 cm a year
   • 9 m 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 east-southeast, where the younger islands lie
   • Toward the west-northwest, where the older islands lie
   • Toward the south, since the Big Island is the youngest

8. 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.

9. 7.

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

   • The Big Island, with the youngest rocks
   • The northernmost seamounts, the oldest in the chain
   • Kauai, with rocks about 5.5 million years old
   • Midway, with rocks about 28 million years old
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 37 times
    • More than 6 times
    • More than 12.5 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?

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

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