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

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

   • A much thicker crust, about 2,000 km deep
   • Iron would float to the top
   • 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?

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

5. 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.

6. 4.

   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
   • Agree: the crust is the densest layer, since it holds the iron
   • Disagree: the inner core is liquid
7. 5.

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

   • Disagree: the spinning liquid outer core creates it
   • Agree: the crust holds a huge magnet
   • Agree: the solid inner core is a bar magnet
   • Disagree: Earth has no magnetic field
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 11%
   • About 1%
   • About 50%
   • About 0.01%

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?

    • About 50%
    • About 3.7%
    • Under 1%
    • 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)?

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

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

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

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