How people are changing Earth's systems

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Paving covers soil with a surface that rain cannot soak into, so the rain runs off into streams (USGS, EPA). Ari traces paving through Earth's systems. Which pair changes first, then next?

   • The hydrosphere (water) alone, since the land surface stays the same
   • The geosphere (land surface), then the hydrosphere (stream flow)
   • The biosphere (plants), then the atmosphere (air), with no change in water
   • The atmosphere (air), then the geosphere (rock), since rain falls from the air
2. 2.

   Clearing a forest removes plants that store carbon, and bare soil can vent carbon (NASA). Bo follows a cleared forest. Which two systems change, and how?

   • The biosphere loses plants, and the atmosphere gains CO₂
   • The biosphere alone changes, since plants are the thing that gets removed
   • The atmosphere loses plants, and the biosphere gains CO₂
   • The hydrosphere loses plants, and the geosphere gains CO₂
3. 3.

   A dam slows river water, so sediment settles in the reservoir (USGS). Kira traces a dam through three systems. Which statement matches the card?

   • Atmosphere: water slows. Geosphere: sediment is lost from the river
   • Hydrosphere changes alone; the sediment stays in motion past the dam
   • Hydrosphere: water slows. Geosphere: sediment piles up in the reservoir
   • Hydrosphere: water speeds up. Geosphere: sediment is carried farther along

4. Read this first

   Where rain goes as land is paved (USGS, from FISRWG 1998)

   Ground cover	Evapotranspiration	Runoff	Shallow infiltration	Deep infiltration
   Natural ground cover	40%	10%	25%	25%
   10–20% impervious	38%	20%	21%	21%
   35–50% impervious	35%	30%	20%	15%
   75–100% impervious	30%	55%	10%	5%

5. 4.

   How does deep infiltration change from natural ground to 75–100% impervious cover, by Luz's reading?

   • It rises from 5% to 25% of the rain
   • It falls from 25% to 10% of the rain
   • It falls from 25% to 5% of the rain
   • It falls by 5 percentage points of the rain
6. 5.

   At 35–50% impervious cover, what share of rain soaks into the ground (shallow plus deep), by Milo's math?

   • 30%, the runoff share
   • 20%, the shallow share alone
   • 65%, the share that does not soak in
   • 35%
7. 6.

   Runoff carries oil, dirt, chemicals and fertilizers. Roads, lots and rooftops keep rain from soaking in. Why does runoff from a city block carry oil and fertilizer into a stream, by Pia's reading?

   • Streams make their own oil and fertilizer from the sediment they carry
   • Rain soaks into the soil and brings oil and fertilizer up to the stream
   • Water that cannot soak in runs across surfaces and picks up what lies on them
   • Pavement makes oil and fertilizer when rain falls on it

8. Card (EPA)

   a city block makes more than 5 times the runoff of a same-size woodland. Model data: the woodland gives 200 gallons.

9. 7.

   A woodland gives 200 gallons of runoff in a storm (model data). A same-size city block gives more than 5 times that. At least how much, by Ren's math?

   • About 100,000 gallons
   • About 205 gallons
   • About 40 gallons
   • More than 1,000 gallons

10. Card

    NOAA says the ocean absorbs about 30% of the CO₂ people release. Model data: 10 billion tons released in a year.

11. 8.

    People release 10 billion tons of CO₂ in a year (model data). About how much does the ocean take up, by Tala's math?

    • About 3 billion tons
    • About 30 billion tons
    • About 0.3 billion tons
    • About 7 billion tons

12. Card (NOAA)

    The ocean absorbs CO₂ from the air. Surface pH has fallen about 0.1. A lower pH means a more acidic solution.

13. 9.

    Surface ocean pH has fallen about 0.1 as the ocean takes up CO₂. What does that mean, and which systems exchange the CO₂, by Zee's reading?

    • The seawater is unchanged, since CO₂ stays in the air above the ocean
    • The seawater is more acidic, and CO₂ moves from the atmosphere to the hydrosphere
    • The seawater is less acidic, and CO₂ moves from the atmosphere to the hydrosphere
    • The seawater is more acidic, and CO₂ moves from the hydrosphere to the atmosphere
14. 10.

    Deforestation was 16 million hectares a year in 1990–2000 and 10 million hectares a year in 2015–2020. Esme reads the forest numbers. Which statement is right?

    • The yearly loss rose by 6 million hectares between the two periods
    • The yearly loss fell by 6 million hectares, but forest was still being lost
    • The yearly loss fell to zero, so forest stopped being lost
    • The yearly loss fell by 10 million hectares between the two periods