Forces that build land up and wear it down
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
Read this first
Survey of one range (example data)
Year Summit (m) Valley floor (m) 1900 3,100 1,200 1950 3,106 1,194 2000 3,112 1,188 Ari reads the survey from 1900 to 2000. Which pair of processes best explains both columns?
- Erosion wearing both the summit and the valley floor down over the century
- Uplift raising the summit while a river cuts the valley floor lower
- Deposition filling the valley while uplift lifts the summit
- Uplift raising the summit and the valley floor by equal amounts
Field notes (example data)
Site Observation North ridge clam fossils in layered rock 3,200 m above sea level East flank black lava that cooled last year South coast sand building up at a river mouth Bo sorts the notes. Which site gives the best evidence that uplift raised the land?
- East flank: new lava shows the land is being lifted
- South coast: growing sand shows the crust is rising
- North ridge: sea level must once have stood 3,200 m higher
- North ridge: sea-floor fossils far above the sea show the rock was lifted
Table, Processes and the size they shape (example ranges), with columns Process, Size shaped, Time needed
Frost wedging, one boulder, about 1 m, days to years; River cutting, a valley, about 10 km, thousands of years; Plate collision, a mountain belt, about 1,000 km, millions of years.
A mountain belt stretches about 1,000 km. Kira checks the table. Which process can build land on that scale?
- Frost wedging, since many cracked boulders slowly add up to a whole mountain belt
- River cutting, which shapes valleys about 10 km wide
- Frost wedging, since it works fastest, in days to years
- Plate collision, which raises crust over about 1,000 km in millions of years
Cliff base, sharp-edged, 40 cm; River, 5 km on, rounded, 8 cm; Delta, 40 km on, rounded, 0.05 mm. Jun follows grains downstream. Which statement fits the table?
- Erosion broke the cliff rock in place; weathering then carried the grains downstream
- Weathering broke the rock at the cliff; moving water then wore the pieces smaller and rounder
- Deposition made the grains smaller and rounder as they settled at each place
- Chemical weathering alone shrank the grains; flowing water merely moved them
Use this
Table, Stream speed and the largest grain it carries (example data), with columns Speed (m/s), Largest grain carried: 1.0, gravel, 10 mm; 0.5, sand, 1 mm; 0.1, silt, 0.05 mm.
A stream moving 1 mm sand at 0.5 m/s enters a lake and slows to 0.1 m/s. What does Milo predict for the sand?
- It keeps moving, since water that once carried it will carry it anywhere it goes
- It settles out as a delta, since 0.1 m/s carries only grains up to 0.05 mm
- It breaks into silt by weathering and keeps moving
- It dissolves in the lake water as chemical weathering
A, neutral, still, 0.1; B, acid rain, still, 0.8; C, neutral, shaken daily, 0.2. Noah compares the beakers. Which kind of weathering do the data show most strongly?
- Erosion: the water carried 0.8 g of limestone away
- Physical: shaking removed the most mass from the chips
- Neither: each beaker lost some mass, so the type of water did not matter
- Chemical: acid water removed 0.8 g, eight times the neutral water
Water expands about 9% in volume when it freezes (ice is about 0.92 g/cm³; water is 1.00 g/cm³). Pia sees 50 cm³ of water freeze in a rock joint. What kind of weathering is this, and how much more room does the ice take?
- Physical: the ice takes up 4.5 cm³ more room and pries the joint wider
- Physical: the ice takes up 0.45 cm³ more room and pries the joint wider
- Chemical: freezing makes new minerals, so the ice takes up 4.5 cm³ more room
- Physical: the ice takes up 45 cm³ more room and pries the joint wider
Iron-rich rock after 10 years (example data)
Site Climate Surface turned rusty (%) A dry desert 5 B humid forest 60 Ren compares the two sites. What do the data say about chemical weathering?
- Water speeds it up: rust covers 60% in the humid forest but only 5% in the desert
- Heat alone speeds it up, since deserts are hotter and still rusted
- Erosion made the rust, since moving water carried iron onto the surface
- Physical weathering made the rust, since the surface cracked in both places
Tala models a range that rises 4 mm a year while erosion wears it down 4 mm a year (example data). What is its height change after 1 million years?
- It gains about 4,000 m, since only uplift changes height
- It gains about 4 m, since 4 mm a year is tiny
- Almost none: 4,000 m of uplift is matched by 4,000 m worn away
- It gains about 8,000 m, since both processes add height
Uplift and erosion at three sites (example data)
Site Uplift (mm/yr) Erosion (mm/yr) X 5 4 Y 1 2 Z 3 3 Zee reads the table. Which site is getting lower?
- No site: each site has uplift, so the three of them rise
- Site X: its erosion rate of 4 mm a year is the highest
- Site Z: erosion equals uplift, so the land must be wearing down
- Site Y: erosion at 2 mm a year beats uplift at 1 mm a year