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?
- 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
- Erosion wearing both the summit and the valley floor down over the century
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?
- 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
- East flank: new lava shows the land is being lifted
- South coast: growing sand shows the crust is rising
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 it works fastest, in days to years
- Frost wedging, since many cracked boulders slowly add up to a whole mountain belt
- River cutting, which shapes valleys about 10 km wide
- 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?
- Weathering broke the rock at the cliff; moving water then wore the pieces smaller and rounder
- Chemical weathering alone shrank the grains; flowing water merely moved them
- Erosion broke the cliff rock in place; weathering then carried the grains downstream
- Deposition made the grains smaller and rounder as they settled at each place
Four observations (example)
Letter Observation A frost splits a boulder where it lies B rain washes the pieces 3 m downhill C acid rain slowly dissolves a limestone ledge D wind drops sand into a dune Luz sorts the observations. Which two are weathering, not erosion or deposition?
- A and C, which break down rock where it lies
- B and C, since water works on rock in both
- A and B, since both start with rock being cracked
- B and D, since both involve the weather
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 breaks into silt by weathering and keeps moving
- 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 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?
- Neither: each beaker lost some mass, so the type of water did not matter
- Physical: shaking removed the most mass from the chips
- Erosion: the water carried 0.8 g of limestone away
- 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
- 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
- Physical: the ice takes up 0.45 cm³ more room and pries the joint wider
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?
- Site Y: erosion at 2 mm a year beats uplift at 1 mm a year
- 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
Esme models uplift of 2 mm a year and erosion of 3 mm a year (example data). What is the net change in height after 10,000 years?
- It rises about 50 m
- It rises about 10 m
- It lowers about 10,000 m
- It lowers about 10 m
