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?
- Deposition filling the valley while uplift lifts the summit
- Erosion wearing both the summit and the valley floor down over the century
- Uplift raising the summit and the valley floor by equal amounts
- Uplift raising the summit while a river cuts the valley floor lower
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
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?
- B and C, since water works on rock in both
- A and C, which break down rock where it lies
- B and D, since both involve the weather
- A and B, since both start with rock being cracked
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 dissolves in the lake water as chemical weathering
- 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
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?
- Physical: shaking removed the most mass from the chips
- Chemical: acid water removed 0.8 g, eight times the neutral water
- Neither: each beaker lost some mass, so the type of water did not matter
- Erosion: the water carried 0.8 g of limestone away
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 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 4.5 cm³ more room and pries the joint wider
- 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?
- Erosion made the rust, since moving water carried iron onto the surface
- Heat alone speeds it up, since deserts are hotter and still rusted
- Water speeds it up: rust covers 60% in the humid forest but only 5% in the desert
- 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?
- Almost none: 4,000 m of uplift is matched by 4,000 m worn away
- It gains about 4,000 m, since only uplift changes height
- It gains about 8,000 m, since both processes add height
- It gains about 4 m, since 4 mm a year is tiny
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 lowers about 10 m
- It rises about 10 m
- It lowers about 10,000 m