How fast plates move

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Hawaiian chain (USGS ages; the bend's distance is example data)

   Place	Age	Distance from the Big Island
   Midway	28 million years	2,600 km
   The bend	43 million years	3,500 km
   Northernmost seamounts	80 million years	6,000 km

2. 1.

   Which stretch of the chain had the fastest average rate, by Esme's math? (1 km = 100,000 cm.)

   • Midway to the bend, at about 6 cm a year
   • The bend to the seamounts, at about 6.8 cm a year
   • They are equal, since the whole chain averages 7.5 cm a year
   • The Big Island to Midway, at about 9.3 cm a year
3. 2.

   India moved about 9 m a century, then slowed by about half. India slowed to about 4.5 cm a year, half its earlier rate. How long does it take to move 450 km at that rate, by Kira's math? (1 km = 100,000 cm.)

   • About 10 million years
   • About 20 million years
   • About 100 million years
   • About 1 million years
4. 3.

   1 cm a year is 10 km per million years. Plate A moves 7 cm a year. Plate B moves 80 km per million years. Which is faster, and by how much, by Luz's math?

   • Plate A, by 73 cm a year
   • Plate A, by 1 cm a year
   • Plate B, by 73 cm a year
   • Plate B, by 1 cm a year
5. 4.

   a GPS station moves 24 cm in 4 years. USGS: 1 cm a year is 10 km per million years. A GPS station moves 24 cm in 4 years (example). What is that rate in km per million years, by Milo's math?

   • About 60 km per million years
   • About 6 km per million years
   • About 600 km per million years
   • About 96 km per million years
6. 5.

   GPS measures movement now. Dated stripes and dated volcanoes give rates over millions of years. A team wants a plate's average speed over the last 5 years. Which data fit, by Noah's reasoning?

   • Dated stripes laid down over millions of years
   • The age of one volcano on the plate
   • GPS station positions over the 5 years
   • The width of the ocean at the ridge today
7. 6.

   The Hawaiian chain's northernmost seamounts are about 80 million years old and about 6,000 km from the Big Island. A team wants a plate's average speed over the last 80 million years. Which data fit, by Pia's reasoning?

   • The ages and distances of the volcanoes along the chain
   • The age of the Big Island alone, which is under 0.7 million years
   • Two GPS readings taken a year apart, one in spring and one in autumn
   • The height of Kauai above the sea, compared with that of Midway

8. Card (example data)

   Stripe 1 is 10 million years old and stripe 2 is 14 million years old, 100 km farther from the ridge.

9. 7.

   Two stripes are 10 and 14 million years old, and 100 km apart (example). What spreading rate do they give, by Ren's math? (1 km = 100,000 cm.)

   • 0.7 cm a year
   • 2.5 cm a year
   • 1 cm a year
   • 0.4 cm a year

10. Pacific Plate rates by method (USGS)

    Method	Span	Rate
    GPS	today	6 cm a year
    Midway's age	28 million years	9.3 cm a year
    Whole chain	80 million years	7.5 cm a year

11. 8.

    Which statement about the Pacific Plate's rate is supported by the table, by Tala's reading?

    • The rate is 9.3 cm a year, and the other values are measurement errors
    • The rate depends on span and method: 6 today, 9.3 over 28 million years, 7.5 over 80
    • The rate rises with the span, from 6 up to 9.3 cm a year
    • The rate is 6 cm a year, since GPS is the sole method that counts
12. 9.

    A news item says the Pacific Plate moves 6 cm a year. Which fuller statement fits the table, by Zee's reading?

    • About 9.3 cm a year today by GPS; hotspot ages give 6 to 7.5
    • Between 6 and 9.3 cm a year, depending on which GPS station is used
    • Exactly 6 cm a year at each moment, as GPS shows
    • About 6 cm a year today by GPS; hotspot ages give 7.5 to 9.3 over longer spans
13. 10.

    The Pacific Plate moves about 6 cm a year today. Midway's age gives about 9.3 cm a year. By about what percent is 9.3 cm a year faster than 6 cm a year, by Ari's math?

    • About 35%
    • About 155%
    • About 3.3%
    • About 55%