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?

   • The Moon's core is liquid like Earth's outer core
   • Outer layers were iron-poor, so the Moon got little iron
   • The Moon's iron rose to its surface
   • The Moon formed already layered with no iron
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
   • The same layers as today
   • Little sorting, so no distinct iron core

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 must be made of light rock
   • It likely has a large iron core
   • It did not form layers
5. 4.

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

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

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

   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 11%
   • About 0.01%
   • About 50%

9. Radii (NASA, USGS)

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

10. 7.

    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 3.7%
    • About 50%
    • About 19%
11. 8.

    Plate tectonics recycling crust into the mantle. Why are no rocks left from Earth's first few hundred million years, by Tala's reading (USGS)?

    • Earth had no crust until recently
    • Plate tectonics has recycled Earth's oldest rocks
    • Earth formed just 4 billion years ago
    • The first rocks sank into the core as heavy iron long ago

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?

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

    Four evidence cards, labeled A to D. Which evidence best supports the sorting (differentiation) model, by Bo's reading?

    • A crust thousands of km thick
    • Each layer having the same makeup
    • The crust being the densest layer
    • A dense metal core under lighter rocky layers