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
- Uplift raising the summit and the valley floor by equal amounts
- 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
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?
- Plate collision, which raises crust over about 1,000 km in millions of years
- 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
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 B, since both start with rock being cracked
- B and D, since both involve the weather
- A and C, which break down rock where it lies
- B and C, since water works on rock in both
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 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
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?
- Chemical: acid water removed 0.8 g, eight times the neutral water
- 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
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 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 0.45 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?
- Physical weathering made the rust, since the surface cracked in both places
- 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
- Erosion made the rust, since moving water carried iron onto the surface
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 8,000 m, since both processes add height
- 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 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 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
- 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
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 10,000 m
- It rises about 10 m
- It lowers about 10 m