How water's properties change rock and land
Grade 9 Science Worksheet
Circle the best answer.
Read this first
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?
- Frozen days: A has 120 against 60, so A's count must be a mistake
- Thawing ice shrinks and pulls cracks apart, so warming will not change A
- Freeze-thaw cycles, so warming that adds cycles at A raises its rockfall
- How cold it gets: A is colder, so warming will lower A's 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 slows down as ice packs the crack and keeps more water out
- It reverses: the crack narrows as ice contracts while freezing
- 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
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
- More rain dissolved A's limestone faster than B's after 1990
- Natural dissolving, since both counties sit on the same limestone
- 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?
- Ten times the soil carbon dioxide outweighs cold water's solubility
- Rain is equal at both sites, so the two rates should be the same
- Heat itself dissolves limestone, so the warmer site must win
- The data must be wrong, since cold water should dissolve more rock
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
- Low winter cave carbon dioxide lets drips degas and drop calcite
- Winter rain is more acidic, so it carves the stalactite faster
- Cold slows chemistry, so winter growth ought to be the slower
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: it carries the most water, 100 m³/s
- Reach A: it is middling on both, so it balances out
- Reach C: its gentle slope slows the water so it scours
- Reach B: 20 × 0.010 = 0.20 is the largest product
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 dam held back water, so the river below sank as it dried
- 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 reservoir slowed the water, so it drops more sediment below
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?
- Sediment cut-off: retreat began when supply fell; sea-level rise held steady
- Stronger waves after 1970, as the sudden retreat itself shows
- Sea-level rise: the sea kept rising, so the delta is drowning
- Both causes equally, as each record changed by the same amount
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
- Certain: 30 ÷ 10 = 3 floods, which is a 300% chance
- Unsafe: 10% each year makes about 96% over 30 years
- Safe: one just happened, so the next is about 10 years off
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?
- Levees kept flow off the floodplain, so it passed as a higher crest
- More rain must have fallen in the years after the levees went up
- The levees slowed the water, so the river bed filled with sediment
- Levees made the river carry less water past the town downstream