Worksheet

Two Islands, Two Wet Sides: Wind Belts and Landslides

Grade 6 earth science: a spinning-disk model and rain, landslide and quake records from two islands show how heating and Earth's spin set wind belts.

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1 NGSS standard
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11 questions
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Format: Interactive · Printable
Grade: Grade 6
Subject: Science
Question types: Fill in the blank, Multiple choice, Matching, Circle the answer, Sorting, Short answer

About this worksheet

What students practice

Students use a rotating-disk model to explain how Earth's rotation curves moving air in each hemisphere.
Students combine uneven heating and Earth's rotation to predict wind directions at different latitudes.
Students use rain and landslide data to explain why the wet side of a mountain ridge changes with latitude.

How to use

If you can, spin a paper plate on a lazy Susan and draw a straight line across it before students start. Have them name the wind direction at each latitude before answering Section 2.

Curriculum

NGSS standard covered

MS-ESS2-6

Model how uneven heating and Earth's rotation cause patterns of atmospheric and ocean circulation that shape climate.

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Two Islands, Two Wet Sides: Wind Belts and Landslides

Use a spinning-disk model and island records to explain which mountain slope gets the rain.

The spinning-disk model

Read the passage and the disk data, then answer the questions.

Why One Side of the Island Slides

1Ridgeback is a mountain town on Kestrel Island, a large island at about 45° north latitude (45°N). A steep ridge runs from north to south down the middle of the island, with open ocean on both sides. The town's hazard office, run by Mr. Bertrand Okoye, keeps records of landslides and earthquakes. Sixth graders Odette Laurent and Kwame Boateng, who volunteer at the office, noticed that the towns on the west slope have many more landslides than the towns on the east slope. They compared Kestrel Island with Palmetto Island, which has the same kind of north–south ridge but lies at about 18°N. The islands and their numbers are made up, but the patterns are based on real places.

2Mr. Okoye explained that most landslides on both islands happen during or after long, heavy rains, when soaked soil grows heavy and slips. A smaller number are set off by earthquakes.

3The students started with a model of how air moves around Earth. Sunlight strikes Earth most directly near the equator, so the air there is heated the most. This warm air rises, spreads toward the poles high in the atmosphere, cools and sinks back to the surface at about 30°N and 30°S. Near the surface, part of the sinking air flows back toward the equator. Between about 30° and 60° latitude, surface air flows the other way, away from the equator and toward the pole.

4To see how Earth's spin changes the path of moving air, the students built a second model. They taped a paper disk with a radius of 20 cm onto a turntable. While Kwame turned the disk slowly, Odette slid a marker along a ruler that did not move, from the center of the disk toward a dot at its edge, taking about 1 second for each line. A counterclockwise spin stands for Earth as seen from above the North Pole, and a clockwise spin stands for Earth as seen from above the South Pole. For each line, they measured how far its end landed from the dot and noted which side of the dot it was on, looking from the center toward the dot. Each result is the average of 3 trials.

5Air over the ocean picks up water vapor. When the wind pushes moist air up a mountain slope, the air cools, and much of its water vapor condenses into clouds and rain. By the time the air crosses the ridge and sinks down the other side, it has lost much of its water.

Table 1. Spinning-Disk Model (average of 3 trials)
Spin direction	Turns per minute	Line ended from dot (cm)	Side of the dot
No spin	0	0	On the dot
Counterclockwise	2	4	Right
Counterclockwise	4	8	Right
Counterclockwise	6	13	Right
Clockwise	4	8	Left

Use Table 1.

With a counterclockwise spin, the line ended cm farther from the dot at 6 turns per minute than at 2 turns per minute.

Which conclusion does Table 1 support best?

A. A faster spin made the line curve more, and the spin direction set which way it curved.
B. The line curved the same amount at every speed, as long as the disk was turning.
C. The line curved more when the disk turned slowly, because the marker had more time.
D. A counterclockwise spin made the line curve to the left of the dot.

Use paragraph 4. What does the clockwise trial stand for in the model?

A. Warm air rising near the equator before it spreads toward the poles
B. Air moving across the Southern Hemisphere, where its path curves to the left
C. Cool air sinking near 30°N, where it piles up and stops moving
D. Air moving across the Northern Hemisphere at a slower speed than usual

Use paragraph 3 and the disk model. A wind is named for the direction it blows from: a wind moving toward the south is a wind from the north. Match each place to the surface wind it most likely has.

18°N, where surface air flows toward the equator
45°N, where surface air flows toward the North Pole
18°S, where surface air flows toward the equator
45°S, where surface air flows toward the South Pole

A. Wind from the southwest
B. Wind from the southeast
C. Wind from the northwest
D. Wind from the northeast

Rain, landslides and earthquakes on two islands

Use Table 2, the passage and your wind answers.

Table 2. Island Towns (averages for 1995–2024)
Town	Island	Side of ridge	Rain (mm/yr)	Landslides/10 yr	Felt quakes/10 yr
Ridgeback	Kestrel (45°N)	West	2,400	15	6
Ashford	Kestrel (45°N)	East	600	3	7
Saltpan Cove	Palmetto (18°N)	West	500	2	4
Cloudfall	Palmetto (18°N)	East	2,500	16	3

Landslides/10 yr counts every landslide the office recorded near the town, whatever set it off. Felt quakes/10 yr counts earthquakes strong enough for people in the town to feel.

Ridgeback gets times as much rain each year as Ashford.

Which statement best describes Table 2?

A. Both slopes of each island get about the same amount of rain.
B. The towns that feel more earthquakes also get much more rain.
C. On both islands, the west slope gets more rain and more landslides.
D. The west slope is wetter on Kestrel, but the east slope is wetter on Palmetto.

Which explanation of Ridgeback's heavy rain fits the models best?

A. Ridgeback is closer to the equator than Ashford, so stronger sunlight gives it more rain.
B. Winds from the southwest push moist ocean air up the west slope, where it cools and rains.
C. Winds from the northeast carry rain clouds over the ridge and drop them on the west side.
D. Air sinking near 45°N squeezes the water out of the clouds above the west slope.

Kwame wonders whether earthquakes explain why Ridgeback has five times as many landslides as Ashford. What do the data in Table 2 suggest?

A. Earthquakes explain it, because Ridgeback feels 6 earthquakes every 10 years.
B. Earthquakes are not the main reason, because Palmetto Island feels more earthquakes than Kestrel.
C. Earthquakes are not the main reason, because Ashford feels about as many quakes but has far fewer slides.
D. Earthquakes explain it, because both islands feel earthquakes and have landslides.

Underline each fact from Table 2 that is evidence that heavy rain, not earthquakes, explains most of the landslides.

The two wettest towns have the most landslides.Ridgeback feels 6 earthquakes every 10 years.Ashford feels more earthquakes than Ridgeback but has fewer landslides.Both islands have a ridge that runs from north to south.Cloudfall feels the fewest earthquakes but has the most landslides.

10.

Each slope below is on a large island with a north–south ridge and ocean on both sides, like Kestrel and Palmetto. Use the wind belts to sort each slope.

West slope of an island at 50°NEast slope of an island at 12°NWest slope of an island at 12°NEast slope of an island at 15°SWest slope of an island at 45°SEast slope of an island at 45°S

Likely the wet, windward slope	Likely the drier, sheltered slope

11.

A visitor asks Mr. Okoye, "Why is the landslide side of the ridge the west slope on Kestrel Island but the east slope on Palmetto Island?" Write a claim, use data from both tables as evidence, and explain your reasoning using uneven heating and Earth's rotation.