K S 3 G E O G R A P H Y T E A C H E R S ’ T O O L K I T : T H E R O L E O F S T O N E S
© Geographical Association, 2014
10
Water table level
below which
soil is permanently wet
C
B
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60
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Soil formation
Soil is a mixture of tiny particles from broken down
fragments of rock, together with the remains of dead
plants, called humus. It also contains water and air. Most
soil has three main layers, as shown in the drawing –
humus, soil and bedrock.
Humus layer – organic material from the remains of
dead plants
Mineral layer – mixture of plant remains and particles
containing minerals
Bedrock layer – hard rock that slowly weathers into
fragments
The type of soil that develops in any place depends on a
number of factors;
• Bedrock – soil usually develops from the underlying
rock, but it may also develop from the weathered
fragments of other rock, carried by water, wind or ice.
• Climate – temperature and rainfall affect the way soil
develops. Generally, the hotter and wetter the
climate, the deeper the soil will be, since weathering
is more rapid.
• Plants and animals – humus is one of the main soil
ingredients, so plants affect soil composition. Plants
and animals also mix the soil and create air spaces.
• Time – soil develops over time so, generally, it
becomes deeper and more clearly layered over time.
• Relief (shape of the land) – soil is easily eroded from
sloping land. Thin soil is found on steep slopes and
deeper soil at the base of the slope.
The drawing below shows three soils in the same area –
one on the hilltop, one on the hillside and one at the
bottom of the hill. Farmers need to consider the location
of the soil before they decide what to grow.
LESSON 8: Information Sheet 8
10
cm)
Humus layer
organic material from
the remains of dead plants
Soil layer
mixture of plant remains
and rock particles
containing minerals
Bedrock layer
hard rock that slowly
weathers into fragments
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70
Depth (cm)
Penrhiw Farm
You will need to read Information Sheet 8 to do this
activity.
Your task
You are the farmer at Penhriw Farm. You have to decide
the best way to use the land at three locations on the
farm. You could choose to grow crops, grass or trees.
• Crops need fertile soil. This is usually the deepest soil
with the most organic matter and minerals in it. The
soil also needs to be well-drained, with no danger of
flooding.
• Grass needs good soil with plenty of minerals to grow
well. It also needs plenty of moisture and can even
survive flooding.
• Trees can grow on a variety of soil, even thin soil with
fewer minerals. Long roots help them to survive dry
conditions.
1. Look at the contour map that shows the relief, or
shape of the land, on the farm. Try to identify areas
of high land and low land, with slopes in between.
Remember the simple rule – the closer the contour
lines the steeper the land.
2. Now, compare the contour map with the farm map,
showing field boundaries. Find the three locations –
A, B and C – on the map. What type of soil would you
expect to find at each location?
3. Decide how to use the land at A, B and C. Choose one
location each for crops, grass and trees. Give reasons
for your decision.
4. Finally, compare your decision with what the farmer
did. Find Penrhiw Farm on Google Earth at postcode
SA44 4PE (your teacher may need to help you). Did
the farmer make the same decision as you? If not,
why not?
K S 3 G E O G R A P H Y T E A C H E R S ’ T O O L K I T : T H E R O L E O F S T O N E S
LESSON 8: Activity Sheet 11
© Geographical Association, 2014
A
B
C
River
Teifi
Penrhiw
Farm
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metres
0 200
metres
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