Lesson 1.6 · Unit 1 · Thinking spatially
Distribution, concentration and pattern: three different questions
Geographers use three separate words for three separate properties of a spatial arrangement, and students frequently treat them as synonyms. Keeping them apart lets you describe a map precisely instead of vaguely.
- Distribution is the general term for how a phenomenon is arranged across space, and the next three properties are the ways of describing it.
- Density is the frequency per unit area, which is the subject of lesson 1.5.
- Concentration is how spread out or bunched the occurrences are within the area. Clustered means bunched; dispersed means spread.
- Pattern is the geometric arrangement: linear, grid, random, radial or centralized.
- Density and concentration are independent. Two areas can have identical density with completely different concentration, and the distinction is the most useful thing in the lesson.
- Change over time is described the same way. A distribution becomes more clustered or more dispersed, and saying which is more precise than saying it changed.
- Pattern usually has a cause you can name: a grid implies deliberate survey, a linear pattern implies a route or a river, and a radial pattern implies a single center.
Where students lose marks: describing a map as "spread out" when asked about density, or quoting a density figure when asked about pattern. Use the word the question uses and answer the property it names.
A constructed comparison. Two invented counties, each ten kilometers square, each containing exactly one hundred farmhouses.
Step one: compute density for both. Each county is 100 square kilometers and contains 100 houses, so density is one house per square kilometer in both. The two counties are identical on this measure.
Step two: describe County One's concentration. Its hundred houses are spaced evenly across the whole area, roughly one per square kilometer everywhere. This is a dispersed distribution.
Step three: describe County Two's concentration. Its hundred houses sit in four groups of twenty-five, each group occupying about one square kilometer, with the remaining ninety-six square kilometers empty. This is a clustered distribution.
Step four: state the finding. Identical density, opposite concentration. Anyone reporting only the density figure would describe the two counties as the same, and anyone living in them would say they are entirely different places.
Step five: now describe pattern for each. County One's houses fall on a regular grid one kilometer apart. County Two's four clusters sit along a single road running east to west. One has a grid pattern and the other a linear pattern.
Step six: infer causes from the patterns. A grid of evenly spaced farmhouses suggests land divided by a rectangular survey system that allocated equal parcels to individual owners. Clusters along a road suggest settlement that grew from a route, with farmers living in villages and traveling out to their fields.
Step seven: predict consequences from the concentration. Dispersed settlement means longer roads, more expensive utilities and services, and greater isolation. Clustered settlement shares infrastructure and supports a shop or school in each cluster while requiring farmers to travel to their land.
Step eight: state the description a geographer would give. Not "there are a hundred houses" but: density one per square kilometer in both; County One dispersed in a grid pattern, County Two clustered in a linear pattern; the difference consistent with rectangular survey against route-based settlement. That is three properties and an inferred cause, which is what the question is asking for.
Questions 1 to 5 are recall. Questions 6 to 10 ask for reasoning.
- What does concentration describe?
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How bunched or spread out the occurrences are within an area: clustered or dispersed
- Name four geometric patterns.
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Linear, grid, random, radial, and centralized
- In the worked example, what is the density of each county?
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One farmhouse per square kilometer in both
- What pattern does each county show?
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County One a grid pattern, County Two a linear pattern
- What does a radial pattern usually imply?
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A single center that the arrangement organizes itself around
- Explain how two areas can have identical density and opposite concentration.
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Because density counts occurrences per unit area and says nothing about where within that area they sit. Both counties contain a hundred houses in a hundred square kilometers, so both have a density of one. County One spreads them evenly, which is dispersed. County Two puts them in four tight groups and leaves ninety-six square kilometers empty, which is clustered. The arithmetic is identical and the places are nothing alike. Density counts how many per area; concentration describes where within it
- What can be inferred from a grid pattern of farmhouses?
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That the land was divided by a deliberate rectangular survey before settlement rather than growing organically. Evenly spaced houses on a regular grid one kilometer apart indicate that equal rectangular parcels were allocated to individual owners who each built on their own land. That is a specific historical process, and it contrasts with patterns that follow rivers, ridges or roads, which indicate settlement responding to existing features. Deliberate rectangular survey allocating equal parcels before settlement
- What practical consequences follow from dispersed rather than clustered settlement?
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Dispersed settlement requires far more road, electricity cable, water pipe and telephone line per household, so infrastructure and service delivery cost more per person, and residents are more isolated. Clustered settlement shares that infrastructure among twenty-five households in a small area and can support a shop or a school in each cluster, at the cost of requiring farmers to travel out to fields they do not live on. Dispersal costs more per household in infrastructure; clustering shares it
- Why is "the distribution changed" an inadequate description?
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Because it does not say which property changed or in which direction. A distribution can become denser without changing concentration, more clustered without changing density, or shift from a grid to a linear pattern with both unchanged. Saying that settlement became more clustered while density held constant is a specific claim that can be checked and explained; saying it changed conveys nothing that could be tested. It does not name which of the three properties moved, or how
- Give the full geographic description of the two counties.
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Density is one farmhouse per square kilometer in both counties. County One is dispersed, with houses spaced evenly, and shows a grid pattern. County Two is clustered, with four groups of twenty-five and most of the county empty, and shows a linear pattern along a road. The difference is consistent with rectangular survey in the first case and route-based settlement in the second. That is three properties and an inferred cause. Equal density; dispersed grid against clustered linear; survey against route