Worksheet

Dust on Highway 9: Forecasting Dust Storms in a Dry Farm Year

Grade 7 earth science: a farm county uses rain, bare-field, wind and crash data to forecast dust storms and judge cover crops and highway warning signs.

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1 NGSS standard
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10 questions
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Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Matching, Circle the answer, Short answer

About this worksheet

What students practice

Students analyze rain, bare-field and wind data to forecast how many dust storms a dry year may bring.
Students use crash rates to judge how well a highway warning system reduces harm from dust storms.
Students match technologies to the part of the dust hazard each one works on.

How to use

Read the extension notes together and talk about why both rain and bare fields matter before students use Table 1. Students can work the crash rates in Table 3 on scrap paper before writing the dust outlook.

Curriculum

NGSS standard covered

MS-ESS3-2

Use data on natural hazards to forecast future events and inform technologies that reduce their effects.

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Dust on Highway 9: Forecasting Dust Storms in a Dry Farm Year

Use rain, field and crash records to forecast dust storms and judge the tools that reduce their harm.

Dry springs and dusty days

Read the extension notes and Table 1, then answer the questions.

Extension Notes: A Dry Spring in Saltgrass County

1Saltgrass County is a farming county on the dry plains of the southwestern United States, where families grow wheat, cotton and sorghum. Strong winds sweep across the county most springs. When the soil is dry and bare, the wind can lift it into a dust storm, a moving wall of dust that can cut how far drivers see on State Highway 9 to a few meters in less than a minute. Crashes involving many cars have happened in these storms. This spring looks dry, so the county's farm extension agent, Ms. Yetunde Halloran, asked Teodora Begay and Callum Nakamura-Reyes, seventh graders in the county farm youth club, to help her plan.

2Wind lifts soil grains only when it blows faster than a certain speed, and that speed depends on the ground. Plants and the stubble left after harvest slow the wind right at the ground, and roots help hold soil in place. Damp soil grains stick to each other. Dust monitors beside fields have recorded the gust speed at which dust starts to blow from different kinds of ground (Table 2).

3Since 2023, the county has paid farmers to plant cover crops, fast-growing plants such as rye that cover a field between one harvest and the next planting. Rows of trees planted along field edges, called windbreaks, also slow the wind, but they take about 10 years to grow tall enough to help.

4In 2020, the state put visibility sensors and electronic signs along a 30 km stretch of Highway 9. When the sensors detect thick dust, the signs lower the speed limit and tell drivers to pull off the road, turn off their lights and take their foot off the brake, so that drivers behind them do not follow their taillights into a crash. A similar 30 km stretch farther west has no sensors (Table 3).

5This year the forecast calls for only about 5 cm of rain from March through May. Many farmers tried to plant cover crops last fall, but the seeds did not sprout in the dry soil, so about 40% of the county's fields are bare this April.

Table 1. Spring records for Saltgrass County
Year	Rain, Mar–May (cm)	Bare fields in April (%)	Dust days on Hwy 9
2018	6	35	9
2019	16	25	1
2020	8	40	8
2021	12	30	3
2022	5	45	12
2023	7	20	4
2024	6	15	3
2025	14	15	1

A dust day is a day when dust cut visibility to less than 1 km somewhere on Highway 9 in the county.

Look at the years 2018 through 2022, before cover crops were paid for. Which pattern do they show?

A. Dust days went up each year from 2018 to 2022, whatever the rain.
B. Springs with less rain and more bare fields usually had more dust days.
C. The number of dust days stayed between 8 and 12 whatever the rain.
D. The wettest springs had the most dust days, since rain loosens the soil.

Springs 2018 and 2024 each had 6 cm of rain, but 2024 had 6 fewer dust days. Which explanation fits the notes best?

A. Cover crops left fewer fields bare in 2024, so less soil was open to the wind.
B. The highway signs from 2020 kept dust from blowing onto the road in 2024.
C. The soil in 2024 was drier, so its grains were too light to stay in the air.
D. The tree windbreaks planted in 2023 had grown tall enough to block the wind.

Use paragraph 5 and Table 1. Which forecast for this spring is best supported?

A. About 1 dust day, like 2025, because cover crops have been paid for since 2023
B. About 3 dust days, like 2024, because this spring has about as little rain as 2024
C. About 8 to 12 dust days, like 2020 and 2022, with as little rain and as many bare fields
D. No forecast is possible, because dust storms start at random on windy days

Wind, ground and warnings

Use Tables 2 and 3 and paragraphs 2 to 4.

Table 2. Gust speed at which dust starts to blow
Kind of ground	Gust speed (km/h)
Bare, dry soil	30
Dry wheat stubble	45
Bare, damp soil	65
Growing cover crop	80

Use Table 2. Dust starts to blow from a growing cover crop only at a gust speed km/h faster than from bare, dry soil.

Tomorrow's forecast calls for gusts up to 55 km/h. It has not rained for three weeks. Circle every kind of ground that is likely to give off dust tomorrow.

Bare, dry soilDry wheat stubbleBare, damp soilGrowing cover crop

Table 3. Two 30 km stretches of Highway 9, 2020–2025
Stretch	Dust days	Crashes in dust
East, with sensors and signs	25	3
West, no sensors	24	12

Find the number of crashes per dust day on each stretch. Write each answer as a decimal; do not round.

East stretch: crashes per dust day
West stretch: crashes per dust day

Why is it more useful to compare crashes per dust day than to compare the total number of crashes on the two stretches?

A. Crashes per dust day count the crashes on clear days as well.
B. Totals would show the east stretch had more crashes than the west.
C. Crashes per dust day show which stretch gets windier springs.
D. The stretches had different numbers of dust days, so totals alone could mislead.

Match each technology or plan to the part of the dust hazard it works on.

Cover crops on fields between harvest and planting
Visibility sensors linked to electronic speed signs
An outlook map of dry soil and next-day wind gusts
Pulling off the road with lights off and foot off the brake

A. Keeps other drivers from following one car into a crash
B. Warns people a day ahead that dust is likely
C. Slows traffic once a storm is crossing the road
D. Lowers the chance that soil lifts at all

Planning for this spring

Use the whole sheet to answer the questions.

The county can pay for one project this spring. Which project is most likely to reduce harm from dust storms on Highway 9 this spring?

A. Add sensors and signs to the west stretch, where dust crashes are more common
B. Pay farmers to plant cover crops this month in the dry, bare fields
C. Plant rows of trees as windbreaks along the fields next to the highway
D. Wait until the first dust storm of the spring before choosing a project

10.

Write a dust outlook for this spring for the county newsletter. Make a claim about how risky this spring will be, use evidence from Tables 1 and 2 and paragraph 5, and explain your reasoning. Then name one technology that will help this spring and one that will help in future years, and say why.