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4th grade · Science · Unit 6 of 8

Rock Layers & Erosion

Weathering, erosion and what rock layers tell us.

What your child practices

Practices how water, ice, wind and plants break down and move rock, and how patterns in rock layers and fossils show how a landscape changed over time.

Arizona Academic Standards learning standard: 4.E1U1.7; 4.E1U1.6 · rock types, fossils and landforms as evidence that Earth changes, and weathering and erosion

How we explain it

Children can open this short lesson before they practice.

  1. Weathering breaks rock. Erosion moves it. Running water moves the most.
  2. Glaciers scrape and carry rock. Roots growing in cracks can split rock.
  3. Over a very long time, erosion can carve deep canyons.
  4. Plants and their roots slow erosion on a hillside.

Example: Which hillside erodes faster in heavy rain: a bare one or a grassy one? Roots hold soil in place. A bare hill has nothing to hold the soil. Answer: the bare hillside

Rock Layers & Erosion in Arizona

In the Arizona Academic Standards, this is unit 6 of 8 in 4th grade Science, after Pushes, Pulls & Forces and before Energy Resources.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Arizona Department of Education

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Rain falling on a slope with no plants will…

    • make new rock
    • wash away less soil
    • grow plants at once
    • wash away more soil

  2. Question 2

    A river carved the Grand Canyon by…

    • one big flood in a day
    • an earthquake
    • wind only
    • erosion over a very long time

  3. Question 3

    Which moves rock and soil the most in a river valley?

    • Sound
    • Moonlight
    • Sunlight
    • Running water

  4. Question 4

    Wind erosion is common in…

    • rainforests only
    • deserts
    • oceans
    • under glaciers

  5. Question 5

    Which slows erosion on a hillside?

    • Pouring water
    • Removing all plants
    • Plants and their roots
    • Digging

  6. Question 6

    The Columbia River Gorge was scoured wider and deeper long ago by…

    • huge Ice Age floods
    • wind in a single day
    • earthquakes
    • a volcano's lava only

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