Heat inside Earth and mantle convection

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Earthquake S waves cannot travel through liquids. S waves from earthquakes do travel through the mantle. Ari reads that plates ride on the mantle. What does card A show about the mantle?

   • The top of the mantle is solid and the rest is liquid
   • The mantle is a liquid, since plates move on it
   • The mantle is a gas, since waves pass through it
   • The mantle is solid rock, even though it flows slowly over time

2. Read this first

   Card

   Hot steel under a steady load bends slowly without melting. USGS: solid mantle rock flows under heat and pressure over millions of years.

3. 2.

   Hot steel bends slowly under a steady load. Bo reads that USGS compares this with mantle rock. What lets mantle rock change shape without melting?

   • Cooling it until it turns brittle and slides along cracks
   • Enough heat to melt it into a liquid first, which then flows
   • A sudden hard blow that shatters the rock into moving pieces
   • Heat and steady pressure acting for a very long time
4. 3.

   a GPS station can detect a shift of 1 cm. The plate under the station moves 3 cm a year. GPS stations show a shift once it reaches 1 cm. Kira wants to know how long a station on a plate needs to show the motion. About how long?

   • About 1 year
   • About 3 years
   • About 30 years
   • About 4 months
5. 4.

   Hot rock is 3.30 g/cm³. Cooler rock beside it is 3.40 g/cm³. USGS: hotter, lighter material rises. Jun compares two pieces of mantle rock side by side. Using the card, which one moves up, and why?

   • The cooler rock rises because it is denser than the hot rock beside it
   • The hot rock rises because it is less dense than the cooler rock
   • The hot rock sinks because it holds more heat energy than the cooler rock
   • Neither moves, since both pieces are solid rock held in place
6. 5.

   In heated soup, hot soup rises in the middle, cools at the top and sinks at the sides. USGS compares mantle convection with thick soup heated in a pot. Milo matches the cool soup that sinks at the pot's side. What plays that part in the mantle?

   • Plates that stay in one place at the surface
   • The hot core at the bottom of the mantle
   • Cold slabs sinking at subduction zones
   • Hot rock rising under a mid-ocean ridge

7. Card (example data)

   Sunlight warms only the top few meters of rock. The mantle starts tens of kilometers down. USGS: Earth's inner heat comes from within.

8. 6.

   A student tells Noah that the Sun heats the mantle. Using the card, what is the best reply?

   • Yes; the top 100 km of mantle gets Sun heat and passes it down by flowing
   • No; sunlight cannot reach it, so the heat comes from decay and leftover heat
   • Yes; surface heat flows down through the crust until the mantle begins to churn
   • No; the mantle has no heat of its own and pressure alone moves the rock

9. Card

   Residual heat is energy left from Earth's formation 4.6 billion years ago. Decay of uranium, thorium and potassium adds heat now (USGS).

10. 7.

    Suppose Earth had only residual heat and no decay. What would Pia predict for the mantle's temperature over billions of years?

    • It would warm up as old heat is released
    • It would cool in a single moment and then stay cold
    • It would stay the same, since the Sun keeps heating it
    • It would cool steadily, with nothing to replace the lost heat
11. 8.

    Rock is a poor conductor, so heat leaves Earth's interior slowly. Radioactive decay adds heat inside (USGS). Earth formed 4.6 billion years ago, yet Ren notes its interior is still hot. Which explanation fits the card best?

    • Heat escapes slowly and decay keeps adding more
    • Sunlight reheats the mantle each day, so it cools very little
    • The mantle is a liquid that traps heat and stops it escaping
    • Rock cannot lose heat, so the heat stays inside
12. 9.

    Gravity slides a plate away from a raised ridge. A cold, dense slab sinking at a trench drags its plate. Zee draws arrow 1 at a raised ridge pushing a plate away, and arrow 2 at a trench pulling it down. Which labels are correct?

    • Both arrows are slab pull
    • Arrow 1 is ridge push; arrow 2 is slab pull
    • Both arrows are ridge push
    • Arrow 1 is slab pull; arrow 2 is ridge push

13. Card

    Plates certainly move a few centimeters a year. How many convection cells exist and how they work is still studied (USGS).

14. 10.

    Esme sorts statements into known and still studied. Which statement about plate motion is supported by USGS?

    • The exact number of convection cells is known, and so is how each one works
    • Scientists have drilled into the cells to map them directly
    • Whether plates move is still unsettled among scientists
    • Plate motion is certain, but the number and structure of cells are unsettled