Chapter 9, Section 3: From Bedrock to Soil
VOCABULARY:
1. soil – a loose mixture of small mineral fragments organic
material, water, and air that can support the growth of
vegetation
2. parent rock – the source of mineral fragments in the soil
3. bedrock – the layer of rock beneath the soil
4. residual soil – soil that remains above its parent rock
5. transported soil – soil that is blown or washed away from its
parent rock
6. humus – dark, organic material formed in soil from the
decayed remains of plants and animals
BIG IDEAS:
-Soil composition
-Soil texture
- describes the kinds and amounts of
different materials in the soil. This
affects the kinds of plants that can
grow in it. Darker soil is richer in
organic material than lighter soil.
-describes the amounts of soil
particles of different sizes that a soil
contains. This affects how easily
water can move into a soil.
-Soil fertility
-PH scale
-describes the ability of the soil to
hold nutrients and to supply
nutrients to plants. These nutrients
come from the parent rock and
humus.
- The lower the ph (0-6), the more
acid there is in the soil. The higher
the ph (8-14) the more basic the soil
is. A PH of 7 is considered neutral.
Most plants grow best in soil with a
ph of 5.5 to 7. Ph is determined by
the parent rock, rainwater and the
use of fertilizers along with chemical
weathering.
How does Climate
affect soil?
- Tropical Climates: the heavy
rain removes the nutrients from the
top layers of soil, thus having poor
soil.
-Deserts and Arctic Climates: There
are not many animals nor plants
that live in these locations, so
humus is not made, leaving the soil
without nutrients.
-Temperate Forests and Grasslands:
The best soil is found here. Medium
amounts of rain, temperature
changes often and many plants and
animals live here to produce humus.
Different layers of Soil:
C horizon: partly weathered
bedrock or sediments from
other locations.
R horizon: bedrock that has not
weathered much.
-Soil Horizons
- Most soil forms in layers
which are horizontal.