Earth's Interior Layers Quiz

Grade 7 · Science · Quiz

10 questions on the crust, mantle, outer core, inner core, and how scientists study Earth's interior.

Questions

1. What is the outermost solid layer of Earth?

   1. Mantle
   2. Crust
   3. Inner core
   4. Outer core
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   Answer: Crust

   The crust is Earth's outermost solid layer. It is the thinnest layer, ranging from 5 km (oceanic) to 70 km (continental) thick.

2. Earth's outer core is in a liquid state.

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   Answer: True

   The outer core extends from about 2,900 km to 5,100 km depth. It is molten iron-nickel that flows and generates Earth's protective magnetic field.

3. Earth's magnetic field is generated by convection in the liquid ___.

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   Answer: outer core

   Convection currents in the liquid outer core's iron-nickel create electric currents, which in turn generate Earth's magnetic field (called the geodynamo).

4. What are seismic waves?

   1. Magnetic waves from the core
   2. Heat waves from the mantle
   3. Vibrations from earthquakes used to study Earth's interior
   4. Sound waves from volcanoes
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   Answer: Vibrations from earthquakes used to study Earth's interior

   Seismic waves are energy waves produced by earthquakes. They travel through Earth and are detected by seismographs; how they behave tells scientists what each layer is made of.

5. The mantle is made primarily of iron and nickel.

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   Answer: False

   The mantle is composed mainly of silicate rocks rich in magnesium and iron. Iron and nickel dominate the CORE, not the mantle.

6. Which type of crust forms the ocean floors?

   1. Granite crust
   2. Continental crust
   3. Oceanic crust
   4. Lithospheric crust
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   Answer: Oceanic crust

   Oceanic crust is the denser, thinner layer made primarily of basalt that forms the ocean floors. Continental crust makes up the land masses.

7. The increase in temperature as you go deeper into Earth is called the ___ gradient.

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   Answer: geothermal

   The geothermal gradient averages about 25–30°C per kilometer in the crust. This heat drives volcanic activity and is used for geothermal energy in some places.

8. Continental crust is thicker than oceanic crust.

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   Answer: True

   Continental crust averages 30–70 km thick (up to 90 km under mountain ranges), far thicker than oceanic crust's 5–10 km.

9. Earth's thickest layer is the:

   1. Crust
   2. Outer core
   3. Mantle
   4. Inner core
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   Answer: Mantle

   The mantle is the thickest layer, spanning roughly 2,830 km and making up about 84% of Earth's total volume.

10. Approximately how deep is Earth's center (radius of Earth)?

    1. 670 km
    2. 2,900 km
    3. 6,371 km
    4. 12,000 km
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    Answer: 6,371 km

    Earth's radius is approximately 6,371 km. The layers from outside in: crust (0–70 km), mantle (70–2,900 km), outer core (2,900–5,100 km), inner core (5,100–6,371 km).

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