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 gas, since waves pass through it
   • The mantle is a liquid, since plates move on 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?

   • Heat and steady pressure acting for a very long time
   • A sudden hard blow that shatters the rock into moving pieces
   • Cooling it until it turns brittle and slides along cracks
   • Enough heat to melt it into a liquid first, which then flows
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 30 years
   • About 3 years
   • About 4 months
   • About 1 year
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 hot rock rises because it is less dense than the cooler rock
   • Neither moves, since both pieces are solid rock held in place
   • The hot rock sinks because it holds more heat energy than the cooler rock
   • The cooler rock rises because it is denser than the hot rock beside it

6. Card

   Hot, lighter rock rises; cold, denser rock sinks (USGS). An ocean plate loses heat to the sea for millions of years.

7. 5.

   Luz follows an ocean plate that cools for millions of years, then reaches a trench. What does the convection idea predict as it goes down?

   • It rises, because rock near a trench is hotter than the mantle around it
   • It melts to liquid at once and stops moving, so nothing is carried down
   • It sinks, because cooling made it denser than the hot mantle around it
   • It floats, because ocean plates are lighter than the land beside the trench
8. 6.

   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?

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

9. 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.

10. 7.

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

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

12. Card

    Slab pull is a cold, dense slab sinking at a trench and dragging its plate. Ridge push is gravity sliding a plate down from a raised ridge.

13. 9.

    Tala studies a plate with a long, cold slab sinking at one edge. Which force fits that edge, using the card?

    • Ridge push, since a sinking slab pushes the plate
    • Ridge push, since the edge is a ridge
    • Tidal pull, since the trench is near the coast
    • Slab pull, acting at the trench edge

14. Card

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

15. 10.

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

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