SCIENCE 7: Origins and Composition of Soils
1.3.1: Investigate and explain various ways in which
rocks can be weathered and explain the rock cycle
1.3.2: Relate various meteorological, geological and
biological processes to the formation of soils.
1.3.3: Investigate and discuss procedures and
expenditures for enriching soils, providing science and
technology examples.
Soils are formed through the combined action of many forces:
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Meteorological forces
a) Weathering __________________________________________________________________
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b) Erosion _____________________________________________________________________
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Geological forces – The movement of the tectonic plates, scraping against each
other, breaks rock into smaller pieces. This movement can also bring new elements
to the surface from deep in the Earth’s crust, which may or may not be helpful to
living things.
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Biological processes
a) Plants ________________________________________________________________________
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b) All living things _______________________________________________________________
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Soils are not created equally. These different forces are different everywhere, as are the minerals
and elements in the rock that is broken down there. Many different things will determine how
productive soil is (how good it is for growing new plant-matter). What are some important things
to have in healthy soil? (List below, and be as specific as possible!)
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You probably listed “dirt” above, which really are small particles of weathered
rock. There are 3 types of “soil particles” that are based on their size. The largest is
__________ (weird, eh?), followed by _________, and the smallest soil particle is
_________--these particles can pack tightly together. The combination of these 3
things in a soil determines most of the other properties that you have listed above.
Now let’s compare soils in three different locations and see how and why they are
different!
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HORIZON O:
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HORIZON A:
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HORIZON B:
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HORIZON C:
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In the grassland, there is lots of ___________________________ because grasses die
off every year. This decaying stuff provides __________________ to new plants, so the
soil is generally productive.
In the forest, trees die less frequently, the layers of _______________________ and
_____________ are shallow. This is good for the trees because it
____________________________________________.
The desert has the least plant life of all, so it has very little ______________. This is not
a good soil for growing!
• Enrichment of Soils:
Soil is a very important resource—all living things need it, either to
grow in, or to grow the food they need to eat! However, only a
small amount of land on Earth has soil that is good for growing
crops. This means we often need to add things or change the soil to
make it right for what we need. In our next class, you will look into
what is needed when growing a particular type of plant here in
Nova Scotia, and consider the science and technology that goes into
developing fertilizers and other materials to optimize (make the
best possible) soil.
• My Choice of Crop: ___________________________________