Data Representation · Lesson 5

Diagrams and labeled models

A diagram in a Science passage shows how something is arranged: layers in the ground, the parts of an apparatus, or the path materials take through a process. It tells you what is above, inside, connected to or flowing into what. The numbers usually sit in a table beside it, so many questions ask you to find a part in the diagram and then look that part up in the table.

Read a diagram in three passes. First, match every label to the part it names. Second, read any scale or measurement written on it: depths, lengths, or arrows that show which way something flows. Third, find the shared names that link the diagram to the table. In the passage below, the link is the layer names.

Then answer from what is drawn and written, not from where a label happens to sit. A label goes wherever it fits; it names a part, and it isn’t a data point. If the diagram doesn’t give a value, look for it in the table.

Layers Under a Field

Students used the drilling records of two wells to draw a cross-section of the ground under a field. They also took a core sample from each layer and measured how fast water moved through it, in centimeters per hour (cm/h).

Figure 1 is the cross-section, drawn to scale. Depths are measured downward from the ground surface, both wells were drilled straight down, and the number beside the bottom of each well gives its total depth.

Table 1 lists the depth of the top and bottom of each layer and the water flow rate measured in its sample.

Table 1
LayerDepth of top (m)Depth of bottom (m)Water flow rate (cm/h)
Soil058
Sandstone51536
Shale15200.5
Limestone203524
For each layer, the depth of its top and bottom in meters and the water flow rate through its sample in cm/h. Soil: 0 to 5 m, 8.0 cm/h. Sandstone: 5 to 15 m, 36.0 cm/h. Shale: 15 to 20 m, 0.5 cm/h. Limestone: 20 to 35 m, 24.0 cm/h. Water moved fastest through sandstone and slowest through shale.

Worked example Easy

Show the whole passage

Layers Under a Field

Students used the drilling records of two wells to draw a cross-section of the ground under a field. They also took a core sample from each layer and measured how fast water moved through it, in centimeters per hour (cm/h).

Figure 1 is the cross-section, drawn to scale. Depths are measured downward from the ground surface, both wells were drilled straight down, and the number beside the bottom of each well gives its total depth.

Table 1 lists the depth of the top and bottom of each layer and the water flow rate measured in its sample.

Table 1
LayerDepth of top (m)Depth of bottom (m)Water flow rate (cm/h)
Soil058
Sandstone51536
Shale15200.5
Limestone203524
For each layer, the depth of its top and bottom in meters and the water flow rate through its sample in cm/h. Soil: 0 to 5 m, 8.0 cm/h. Sandstone: 5 to 15 m, 36.0 cm/h. Shale: 15 to 20 m, 0.5 cm/h. Limestone: 20 to 35 m, 24.0 cm/h. Water moved fastest through sandstone and slowest through shale.
Figure 1: Cross-section of the ground under the fieldWell AWell B12 m28 mSoilSandstoneShaleLimestone0 m5 m15 m20 m35 m
Figure 1: Cross-section of the ground under the field Cross-section drawn to scale, with depth measured down from the ground surface. Four flat layers, top to bottom: soil from 0 to 5 m, sandstone from 5 to 15 m, shale from 15 to 20 m, and limestone from 20 to 35 m. Depths of 0, 5, 15, 20 and 35 m are marked at the layer boundaries on the left. Two wells go straight down from the surface: Well A, on the left, ends at a dot labeled 12 m, and Well B, on the right, ends at a dot labeled 28 m. Each layer’s name is printed inside it, and the name “Limestone” sits low in its layer.

According to Figure 1, the bottom of Well B is in which layer?

  1. Soil
  2. Sandstone
  3. Shale
  4. LimestoneAnswer

How to solve it

  1. Find Well B in Figure 1, the well on the right.
  2. Follow its line down to the dot where it ends, labeled 28 m.
  3. Match that depth to a layer: limestone runs from 20 m to 35 m, so 28 m is inside the limestone.

Why each choice is right or wrong

  • A. Incorrect. Well B starts in the soil at the surface, but its line continues far below the soil’s bottom at 5 m.
  • B. Incorrect. Well B passes through the sandstone (5 to 15 m), but it doesn’t stop there; sandstone is where Well A ends.
  • C. Incorrect. Well B passes through the shale (15 to 20 m) and keeps going.
  • D. Correct. Well B is 28 m deep, and in Figure 1 the limestone runs from 20 m to 35 m, so the well’s bottom is in the limestone.

Worked example Medium

Show the whole passage

Layers Under a Field

Students used the drilling records of two wells to draw a cross-section of the ground under a field. They also took a core sample from each layer and measured how fast water moved through it, in centimeters per hour (cm/h).

Figure 1 is the cross-section, drawn to scale. Depths are measured downward from the ground surface, both wells were drilled straight down, and the number beside the bottom of each well gives its total depth.

Table 1 lists the depth of the top and bottom of each layer and the water flow rate measured in its sample.

Table 1
LayerDepth of top (m)Depth of bottom (m)Water flow rate (cm/h)
Soil058
Sandstone51536
Shale15200.5
Limestone203524
For each layer, the depth of its top and bottom in meters and the water flow rate through its sample in cm/h. Soil: 0 to 5 m, 8.0 cm/h. Sandstone: 5 to 15 m, 36.0 cm/h. Shale: 15 to 20 m, 0.5 cm/h. Limestone: 20 to 35 m, 24.0 cm/h. Water moved fastest through sandstone and slowest through shale.
Figure 1: Cross-section of the ground under the fieldWell AWell B12 m28 mSoilSandstoneShaleLimestone0 m5 m15 m20 m35 m
Figure 1: Cross-section of the ground under the field Cross-section drawn to scale, with depth measured down from the ground surface. Four flat layers, top to bottom: soil from 0 to 5 m, sandstone from 5 to 15 m, shale from 15 to 20 m, and limestone from 20 to 35 m. Depths of 0, 5, 15, 20 and 35 m are marked at the layer boundaries on the left. Two wells go straight down from the surface: Well A, on the left, ends at a dot labeled 12 m, and Well B, on the right, ends at a dot labeled 28 m. Each layer’s name is printed inside it, and the name “Limestone” sits low in its layer.

Based on Figure 1 and Table 1, what was the water flow rate in the sample from the layer directly above the layer in which Well B ends?

  1. 0.5 cm/hAnswer
  2. 8.0 cm/h
  3. 24.0 cm/h
  4. 36.0 cm/h

How to solve it

  1. From Figure 1, Well B is 28 m deep, so it ends in the limestone (20 to 35 m).
  2. Find the layer directly above the limestone: the shale, from 15 m to 20 m.
  3. Look up the shale in Table 1: its flow rate is 0.5 cm/h.

Why each choice is right or wrong

  • A. Correct. Well B ends in the limestone (20 to 35 m). The layer directly above it is the shale (15 to 20 m), and Table 1 gives the shale a flow rate of 0.5 cm/h.
  • B. Incorrect. 8.0 cm/h is the soil’s rate. The soil is the top layer, three layers above the limestone.
  • C. Incorrect. 24.0 cm/h is the rate for the limestone itself, the layer Well B ends in, not the layer above it.
  • D. Incorrect. 36.0 cm/h is the sandstone’s rate. The sandstone is two layers above the limestone, and it is the layer where Well A ends.

Trap Reading meaning into where a label sits

Labels go wherever there is room. In Figure 1, the name “Limestone” sits near the bottom of its layer, close to where Well B ends, but the label’s position tells you nothing about the layer’s depth or about Well B. The limestone runs from 20 m to 35 m, and Well B ends at 28 m because its line stops there. Read depths from the scale or the table, and read where a line or arrow ends, not where a label happens to be.