How Earth formed and separated into layers

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   The Moon's iron core is small compared with Earth's (NASA). How does that fit the idea that the Moon formed from material flung out of Earth's outer layers, by Esme's reading?

   • Outer layers were iron-poor, so the Moon got little iron
   • The Moon formed already layered with no iron
   • The Moon's core is liquid like Earth's outer core
   • The Moon's iron rose to its surface
2. 2.

   If early Earth had never become hot enough to partly melt, what would the model predict, by Jun's reading?

   • Iron would float to the top
   • A much thicker crust, about 2,000 km deep
   • Little sorting, so no distinct iron core
   • The same layers as today

3. Read this first

   Density (NASA)

   Planet	Density (kg/m³)
   Mercury	5,429
   Earth	5,514
   Mars	3,934

4. 3.

   Mercury has a very high density for its size (5,429 kg/m³, NASA). What does the sorting model suggest about it, by Kira's reading?

   • Its magnetic field makes it dense
   • It did not form layers
   • It likely has a large iron core
   • It must be made of light rock
5. 4.

   Luz's friend says Earth formed with its layers already in place. Which response is best?

   • Disagree: Earth has no layers
   • Agree: planets form fully layered
   • Agree: the core was added last
   • Disagree: the layers formed later, as iron sank through hot Earth

6. Table, Earth's layers (USGS), with columns Layer, Thickness, State

   Crust, about 5 km (oceans) to 30 km (continents), solid, brittle; mantle, about 2,900 km, hot, semi-solid rock; outer core, about 2,200 km, liquid iron-nickel; inner core, about 1,250 km, solid iron-nickel.

7. 5.

   Milo's cousin says the crust is the thickest layer because we stand on it. Which response is best (USGS)?

   • Agree: the crust is thousands of km deep
   • Agree: the crust is the densest layer, since it holds the iron
   • Disagree: the crust is far thinner than the mantle
   • Disagree: the inner core is liquid
8. 6.

   Noah's friend says Earth's magnetism comes from a giant magnet buried in the crust. Which response is best (USGS)?

   • Agree: the crust holds a huge magnet
   • Disagree: Earth has no magnetic field
   • Agree: the solid inner core is a bar magnet
   • Disagree: the spinning liquid outer core creates it
9. 7.

   Studies suggest Earth's core had mostly formed within its first tens of millions of years. What fraction of Earth's 4.54-billion-year age is 50 million years, by Pia's math?

   • About 1%
   • About 50%
   • About 0.01%
   • About 11%

10. Radii (NASA, USGS)

    Body	Radius (km)
    inner core	1,221
    Earth	6,375

11. 8.

    The inner core's radius is about 1,221 km (NASA); Earth's radius is about 6,375 km. What fraction of Earth's volume is the inner core (radius ratio cubed), by Ren's math?

    • Under 1%
    • About 50%
    • About 19%
    • About 3.7%

12. Model planet (model data)

    Quantity	Density (kg/m³)
    average	3,000
    surface rock	3,000

13. 9.

    A planet's average density equals its surface rock's density. What would that suggest, by Zee's reading?

    • Little or no dense iron core
    • A crust thousands of km thick
    • A huge iron core
    • A liquid inner core
14. 10.

    The outer core shown frozen solid. If Earth's outer core cooled and froze solid, what would happen to the magnetic field, by Ari's reading?

    • Nothing; the inner core is already liquid
    • It would weaken, since the moving liquid makes it
    • Nothing would change, since the crust makes the field
    • It would grow stronger