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.

   The plate moved 9.3 cm a year from the Big Island to Midway. What was its rate from Midway to the bend, and how does it compare, by Bo's math? (1 km = 100,000 cm.)

   • About 60 cm a year, much faster than 9.3
   • About 9.3 cm a year, the same as before
   • About 6 cm a year, faster than 9.3
   • About 6 cm a year, slower than 9.3
3. 2.

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

   • 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
   • Midway to the bend, at about 6 cm a year
   • The bend to the seamounts, at about 6.8 cm a year
4. 3.

   The whole chain averages 7.5 cm a year. Why does that differ from the 9.3 and 6 cm a year of two stretches, by Jun's reasoning?

   • The stretches are measured in different units, so they cannot be compared
   • An average over 80 million years mixes faster and slower stretches
   • The 7.5 value is an error, because each stretch must give the same rate
   • The 7.5 value was measured by GPS, so it differs from the dated stretches
5. 4.

   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 1 cm a year
   • Plate B, by 73 cm a year
   • Plate A, by 73 cm a year
   • Plate B, by 1 cm a year
6. 5.

   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 6 km per million years
   • About 96 km per million years
   • About 60 km per million years
   • About 600 km per million years
7. 6.

   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?

   • The width of the ocean at the ridge today
   • Dated stripes laid down over millions of years
   • GPS station positions over the 5 years
   • The age of one volcano on the plate
8. 7.

   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?

   • 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
   • The ages and distances of the volcanoes along the chain
   • The age of the Big Island alone, which is under 0.7 million years

9. Card (example data)

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

10. 8.

    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

11. 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

12. 9.

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

    • The rate rises with the span, from 6 up to 9.3 cm a year
    • The rate depends on span and method: 6 today, 9.3 over 28 million years, 7.5 over 80
    • The rate is 6 cm a year, since GPS is the sole method that counts
    • The rate is 9.3 cm a year, and the other values are measurement errors
13. 10.

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

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