How water's properties change rock and land
Grade 9 Science Worksheet
Circle the best answer.
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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 slows down as ice packs the crack and keeps more water out
- It is steady, about 0.25 mm a year, since each winter is the same
- It speeds up: a wider crack holds more water to wedge next winter
- 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?
- Pumping: A's sinkholes rose as its water table fell; B's did not
- 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
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?
- Heat itself dissolves limestone, so the warmer site must win
- Rain is equal at both sites, so the two rates should be the same
- The data must be wrong, since cold water should dissolve more rock
- Ten times the soil carbon dioxide outweighs cold water's solubility
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 B: 20 × 0.010 = 0.20 is the largest product
- Reach C: it carries the most water, 100 m³/s
- Reach C: its gentle slope slows the water so it scours
- Reach A: it is middling on both, so it balances out
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)
Before the dam, 1940–1969: sediment to the delta 12 million tonnes a year, shoreline steady, sea level rising 3 mm a year. After the dam, 1970–1999: sediment 1 million tonnes, shoreline retreating 20 m a year, sea level rising 3 mm a year.
The same river's delta is shrinking (example data). Pia must separate natural and human causes. Which conclusion do the records support best?
- Both causes equally, as each record changed by the same amount
- Stronger waves after 1970, as the sudden retreat itself shows
- Sea-level rise: the sea kept rising, so the delta is drowning
- Sediment cut-off: retreat began when supply fell; sea-level rise held steady
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?
- Rounded pebbles laid down in neat, sorted layers
- A deep valley lying far below the nearby ridge tops
- Steep valley walls with a stream on the valley floor
- U-shape, scratched bedrock, and boulders mixed with clay
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?
- About 10% risk overall, the same as for a single year
- Unsafe: 10% each year makes about 96% over 30 years
- Safe: one just happened, so the next is about 10 years off
- Certain: 30 ÷ 10 = 3 floods, which is a 300% chance
Card (example data)
Before levees, a 900 m³/s peak spread over the floodplain and gave a 4.0 m crest downstream. After levees, the same 900 m³/s peak gave a 5.2 m crest.
After levees were built upstream, the same peak discharge gives a crest 1.2 m higher downstream (example data). Which explanation does Zee choose?
- More rain must have fallen in the years after the levees went up
- Levees made the river carry less water past the town downstream
- The levees slowed the water, so the river bed filled with sediment
- Levees kept flow off the floodplain, so it passed as a higher crest