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Worksheet Grade 7 Art & Music

Drawing the Layers Under Thrushcombe: A Cross-Section Worksheet

Grade 7 students plan a library panel from a fictional well log, choosing mark patterns and one-color emphasis and computing drawn layer heights from a scale.

Objectives

  1. Students will choose mark patterns whose shape and density communicate grain size, value, and the role of each underground layer.
  2. Students will compute drawn heights and a vertical exaggeration from the scales of a cross-section panel.
  3. Students will use a single accent color to give the aquifer emphasis and explain how isolation creates a focal point.

Vocabulary

Aquifer
An aquifer is an underground layer of rock, sand, or gravel that holds water in the tiny spaces between its grains. Wells reach down into aquifers to bring water up to the surface.
Water table
The water table is the underground level below which the ground is completely soaked with water. Dig a hole deeper than the water table and it will start filling with water.

Also: cross-section, well screen, texture, value, emphasis, vertical exaggeration

Teacher overview

The town of Thrushcombe and its well field are fictional. The Thrushcombe Public Library is making a wall panel that shows visitors what lies under the town, drawn from the driller's log for Well 3, and students plan that panel on this worksheet. Part A asks them to judge mark patterns by how their shape and spacing describe each material, Part B has them size the layers from the panel's scales, and Part C asks where the panel's single accent color should go and why.

Teaching note: many students picture groundwater as an underground lake or river flowing through a cave. In most aquifers, including the one in this scenario, the water fills the small spaces between grains of sand and gravel. The panel design makes this visible: the blue tint goes on a layer of gravel, drawn as grains, not on an open pool. A second, design-side misconception is that more color always makes a diagram clearer. Items 13 through 15 test this directly, because a panel with one accent color has an obvious focal point while a panel in which every layer is bright has none. Items 11 and 12 open a discussion of why a panel with a stretched vertical scale should tell visitors so.

Drawing the Layers Under Thrushcombe: A Cross-Section Worksheet — Grade 7 Art & Music
Name: ____________________________ Date: ______________

Student Worksheet

The town of Thrushcombe is fictional. Its library is making a wall panel that shows what is under the ground at the town's Well 3. You are helping to plan the drawing. Here is the driller's log for the well in our scenario, measured in feet below the ground.

  • Topsoil: from 0 to 4 feet deep.
  • Fine sand: from 4 to 22 feet deep. The spaces between the grains hold mostly air.
  • Coarse gravel: from 22 to 46 feet deep. The spaces between the pebbles are full of water. This layer is the aquifer that the town pumps from.
  • Clay: from 46 to 58 feet deep. Water moves through clay very slowly.
  • Limestone bedrock: from 58 to 80 feet deep. This is the bottom of the drawing.

The water table, the top of the water-filled layer, is at 22 feet. The well screen is the part of the well pipe with slots that let water in. It runs from 30 to 42 feet deep.

Part A: Marks and patterns

Geologic drawings often use simple mark patterns for each material. The panel's key uses dots for sand, small open circles for gravel, short flat dashes for clay, and a brick pattern for limestone.

  1. Why do small open circles suit gravel better than tiny dots do?
  2. Clay grains are tiny, flat, and packed tightly. What do short flat dashes suggest about clay that dots would not?
  3. On the panel, the sand dots are about 1/8 inch apart. The clay dashes are packed close together. From across the room, which layer will look darker? Explain using the idea of value.
  4. The clay slows water from moving down into the limestone. Describe one mark or line choice that would help visitors see the clay as a barrier.

Part B: Sizing the layers

The panel uses a vertical scale of 1 inch = 4 feet.

  1. How tall, in inches, should the fine sand layer be on the panel?
  2. How tall, in inches, should the coarse gravel layer be on the panel?
  3. How tall, in inches, is the whole drawing from the ground surface to the bottom of the limestone?
  4. The top of the well screen is 30 feet below the ground. How many inches below the top of the drawing should the screen begin?
  5. The panel is 36 inches wide. It shows 360 feet of ground from left to right. How many feet does 1 inch stand for across the panel?
  6. Compare the two scales. How many times more is the drawing stretched up and down than side to side?
  7. A stretched vertical scale makes thin layers easier to see. Name one way it could mislead a visitor.
  8. What should the designer add to the panel so that visitors are not misled by the stretched scale?

Part C: Color and emphasis

The panel's main message is "This layer holds the water that comes out of your tap." The whole panel is drawn in black and gray, and only one layer may be tinted blue.

  1. Which layer should get the blue tint?
  2. Why does using blue in only one place help the message?
  3. A classmate wants to give every layer its own bright color. Explain the problem, using the idea of emphasis.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: Open circles look like larger, rounded pieces, so they show that gravel grains are bigger than sand grains.
    The shape and size of a mark suggest the shape and size of the grains. Dots read as fine grains, and circles read as pebbles.
  2. Answer: They suggest flat grains lying in tight layers, like a stack.
    Dots suggest separate round grains with space around them. Flat dashes packed close together suggest a dense material with little room for water to pass, which fits clay.
  3. Answer: The clay layer will look darker.
    Value is how light or dark an area looks. Marks packed close together cover more of the white paper, so from a distance the eye blends them into a darker gray. The widely spaced sand dots leave more white paper showing, so the sand reads lighter.
  4. Answer: Accept any clear visual signal of a barrier, such as a heavy solid line along the top of the clay.
    Other strong answers: small water arrows in the gravel that point down and stop at the clay, or a thicker, darker pattern in the clay than anywhere else. The answer should name a mark and explain how it shows that water is held back.
  5. Answer: 4.5 inches.
    The sand runs from 4 to 22 feet, so it is 22 - 4 = 18 feet thick. At 1 inch per 4 feet, 18 / 4 = 4.5 inches.
  6. Answer: 6 inches.
    The gravel runs from 22 to 46 feet, so it is 46 - 22 = 24 feet thick, and 24 / 4 = 6 inches.
  7. Answer: 20 inches.
    The drawing goes from 0 to 80 feet, and 80 / 4 = 20 inches.
  8. Answer: 7.5 inches.
    The screen starts 30 feet down, and 30 / 4 = 7.5 inches below the top of the drawing.
  9. Answer: 10 feet.
    360 feet across 36 inches gives 360 / 36 = 10 feet for each inch.
  10. Answer: 2.5 times.
    Across, 1 inch stands for 10 feet. Up and down, 1 inch stands for only 4 feet, so heights are drawn larger. 10 / 4 = 2.5.
  11. Answer: Layers look thicker and deeper compared with their width than they really are.
    A visitor might think the aquifer is much thicker, compared with its width, than it really is, or that the ground surface and the layer boundaries slope more steeply than they do. Any answer that says the shapes look taller or steeper than in real life is correct.
  12. Answer: A note saying the height is stretched 2.5 times, with a separate scale bar for each direction.
    A note alone or two labeled scale bars alone also earn credit if the student explains that it tells visitors the heights are not to the same scale as the widths.
  13. Answer: The coarse gravel layer.
    It is the aquifer. Its spaces are full of water, and the well screen sits inside it, so the water in town taps comes from this layer.
  14. Answer: A single color on a black-and-gray panel becomes the focal point, so the eye goes to the aquifer first.
    This is emphasis by isolation. Because nothing else on the panel competes with the blue, the layer that carries the main message is the first one a visitor sees.
  15. Answer: When every layer is bright, nothing stands out, so the panel has no focal point.
    The colors compete with each other, and the aquifer no longer looks special. Visitors might also think each color means something important, which makes the panel harder to read.

Differentiation

Support

Provide a partly drawn panel strip, 20 inches tall on the scale of 1 inch = 4 feet, with tick marks every inch, so students can count down from the surface to check items 5 through 8. For Part A, give a small sample card showing each mark pattern, so students compare the patterns by eye before explaining them.

Extension

Suppose the fictional library decides to show a second well 200 feet to the east, where the clay layer thins out and ends. Ask students to sketch how the cross-section changes between the two wells, keeping the same patterns and scales, and to write two sentences explaining why the place where the clay ends matters for how fast rain can reach the limestone.

ELL supports

Label a simple sketch of the cross-section with the key terms (topsoil, sand, gravel, clay, limestone, water table, and well screen) before students begin. Let students answer Part A and Part C with a small labeled sketch and a short phrase in place of full sentences, and provide a frame for item 15: "If every layer is bright, then ... so the viewer ...".