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

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

   • The Big Island to Midway, at about 9.3 cm a year
   • They are equal, since the whole chain averages 7.5 cm a year
   • The bend to the seamounts, at about 6.8 cm a year
   • Midway to the bend, at about 6 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 7.5 value was measured by GPS, so it differs from the dated stretches
   • 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
5. 4.

   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 20 million years
   • About 1 million years
   • About 10 million years
   • About 100 million years
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 600 km per million years
   • About 60 km per million years
   • About 6 km per million years
   • About 96 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?

   • 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
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?

   • 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

9. 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

10. 8.

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

    • 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 9.3 cm a year, and the other values are measurement errors
    • The rate is 6 cm a year, since GPS is the sole method that counts
11. 9.

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

    • About 6 cm a year today by GPS; hotspot ages give 7.5 to 9.3 over longer spans
    • 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
12. 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 55%
    • About 3.3%
    • About 155%
    • About 35%