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 iron rose to its surface
   • The Moon formed already layered with no iron
   • The Moon's core is liquid like Earth's outer core
   • 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?

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

3. Read this first

   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.

4. 3.

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

   • Disagree: the inner core is liquid
   • Agree: the crust is the densest layer, since it holds the iron
   • Disagree: the crust is far thinner than the mantle
   • Agree: the crust is thousands of km deep
5. 4.

   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
   • Disagree: Earth has no magnetic field
   • Agree: the crust holds a huge magnet
   • Agree: the solid inner core is a bar magnet
6. 5.

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

7. Radii (NASA, USGS)

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

8. 6.

   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 19%
   • Under 1%
   • About 3.7%
9. 7.

   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
   • Plate tectonics has recycled Earth's oldest rocks
   • Earth had no crust until recently
   • Earth formed just 4 billion years ago

10. Model planet (model data)

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

11. 8.

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

    • A crust thousands of km thick
    • A huge iron core
    • A liquid inner core
    • Little or no dense iron core
12. 9.

    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 would change, since the crust makes the field
    • It would grow stronger
    • Nothing; the inner core is already liquid
    • It would weaken, since the moving liquid makes it
13. 10.

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

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