How water's properties change rock and land
Grade 9 Science Worksheet
Circle the best answer.
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Card (example data)
Site A: 120 days below 0 °C, 8 freeze-thaw cycles, 3 rockfalls a year. Site B: 60 days below 0 °C, 45 freeze-thaw cycles, 31 rockfalls a year. Both cliffs have water in their cracks.
Ari compares rockfall at two cliffs of the same granite (example data). Which explanation fits, and what should warming do at Site A?
- Thawing ice shrinks and pulls cracks apart, so warming will not change A
- How cold it gets: A is colder, so warming will lower A's rockfall
- Frozen days: A has 120 against 60, so A's count must be a mistake
- Freeze-thaw cycles, so warming that adds cycles at A raises its rockfall
Card (example data)
Crack width each spring: 1.0, 1.1, 1.3, 1.6 and 2.0 mm. Each winter the crack fills with water that freezes and thaws many times.
Bo measures one crack in a cliff each spring (example data). Which description of the trend and its cause fits best?
- It speeds up: a wider crack holds more water to wedge next winter
- It is steady, about 0.25 mm a year, since each winter is the same
- It slows down as ice packs the crack and keeps more water out
- It reverses: the crack narrows as ice contracts while freezing
Ice is about 9% less dense than liquid water, so it floats. Liquid water is densest near 4 °C. Water is densest near 4 °C, and ice is about 9% less dense than water. Which prediction does Esme make for a deep mountain lake in a long, cold winter?
- Ice forms on top and insulates; water near 4 °C stays at the bottom
- The whole lake must cool to 0 °C before the first ice can form
- A cold enough winter freezes any deep lake solid within a few weeks
- Ice forms at the bottom, where water is densest, and grows upward
Card (example data)
County A: heavy well pumping from 1990; water table fell 8 m; sinkholes per year 2 before 1990, 14 after. County B: little pumping; water table steady; sinkholes 2 before, 2 after.
Two counties sit on the same limestone and get the same rain (example data). Jun must say what raised sinkholes in County A. Which reading of the data is best?
- Natural dissolving, since both counties sit on the same limestone
- More rain dissolved A's limestone faster than B's after 1990
- New caves filled with stalactites and pressed A's ground down
- Pumping: A's sinkholes rose as its water table fell; B's did not
Card (example data)
Alpine site: water 3 °C, soil air 0.2% carbon dioxide, thin soil. Tropical site: water 25 °C, soil air 2% carbon dioxide, thick soil with roots and decay. Rain is equal.
Cold water holds more carbon dioxide than warm water, yet Kira finds tropical limestone dissolves faster than alpine limestone (example data). Which explanation fits the card?
- Ten times the soil carbon dioxide outweighs cold water's solubility
- The data must be wrong, since cold water should dissolve more rock
- Heat itself dissolves limestone, so the warmer site must win
- Rain is equal at both sites, so the two rates should be the same
Card (example data)
Winter cave air 600 ppm carbon dioxide, growth 0.12 mm a month. Summer cave air 3,000 ppm, growth 0.02 mm a month. Drip water is the same all year.
Luz logs a stalactite's growth and the cave air (example data). Why does it grow faster in winter?
- Winter drips dissolve more calcite and so reshape the stalactite
- Cold slows chemistry, so winter growth ought to be the slower
- Winter rain is more acidic, so it carves the stalactite faster
- Low winter cave carbon dioxide lets drips degas and drop calcite
Card (example data)
Reach A: discharge 50 m³/s, slope 0.002. Reach B: discharge 20 m³/s, slope 0.010. Reach C: discharge 100 m³/s, slope 0.0005.
Stream power grows with discharge × slope. In which reach does Milo expect the gravel bed to erode most (example data)?
- Reach C: its gentle slope slows the water so it scours
- Reach A: it is middling on both, so it balances out
- Reach B: 20 × 0.010 = 0.20 is the largest product
- Reach C: it carries the most water, 100 m³/s
Card (example data)
Suspended sediment above the reservoir 12 million tonnes a year, below the dam 1 million tonnes. Riverbed below the dam lowered 2 m in 30 years. Yearly discharge unchanged.
A dam traps sediment (example data). Discharge below it is unchanged. Why did the riverbed below the dam drop 2 m in 30 years, Noah asks?
- The reservoir slowed the water, so it drops more sediment below
- Clear water leaving the dam picks up bed sediment as a new load
- Sediment is 1/12 as much, so the bed falls 12 times as fast
- The dam held back water, so the river below sank as it dried
Card (example data)
Valley X: U-shaped cross-section, scratched bedrock, unsorted boulders and clay mixed together. Valley Y: V-shaped cross-section, rounded pebbles in sorted layers, a fast stream.
Ren surveys two valleys (example data). Which set of evidence best shows a glacier, not a river, carved Valley X?
- A deep valley lying far below the nearby ridge tops
- U-shape, scratched bedrock, and boulders mixed with clay
- Steep valley walls with a stream on the valley floor
- Rounded pebbles laid down in neat, sorted layers
Card (example data)
49 yearly peak flows; 1,200 m³/s ranks 5th. Recurrence interval T = (49 + 1) ÷ 5 = 10 years, a 10% chance each year.
A 49-year record ranks a 1,200 m³/s flood 5th. A builder says the site is safe for a 30-year home, as such floods come every 10 years and one just happened. Tala's verdict?
- Safe: one just happened, so the next is about 10 years off
- About 10% risk overall, the same as for a single year
- Unsafe: 10% each year makes about 96% over 30 years
- Certain: 30 ÷ 10 = 3 floods, which is a 300% chance