Download Chapter 8 Notes

Chapter 8 Notes
 Weathering is the process
that breaks down rock and
other substances at Earth’s
surface
 Factors that contribute to
weathering
 Heat
 Cold
 Water
 Ice
 O2 & CO2 in the atmosphere
 Examples of weathering
Rust
Peeling paint
 Examples of weathering
Cracking sidewalks
Potholes
 Erosion is the removal of
rock particles by water, wind
& ice or gravity
 Weathering breaks rocks
into smaller pieces and
erosion takes those pieces
away
Mechanical
Weathering
Chemical
Weathering
 Mechanical Weathering is
caused by physically
breaking rocks into smaller
pieces
 Causes of Mechanical Weathering
Freezing
Ice Wedging: process where
wedges of ice in rocks widen and
deepen cracks
Release of
pressure
 Plant growth
 Animals
Abrasion:
grinding
away of
rock by
rock
particles
carried by
erosion
 Chemical Weathering is the
process that breaks down
rock through chemical
changes
Action of water = dissolves rock
 O2 (Oxygen Gas) = oxidation (rust)
CO2 = dissolves in rain water
and forms carbonic acid
Living
organisms =
plants grow
and produce
a weak acid
Acid Rain =
compounds
from burning
fossil fuel to
mix chemically
with rain to
form acid
 Mechanical weathering breaks
rock and makes more surface
area for chemical weathering to
take place
 Rate of weathering affected 2 ways
 Rock type
More permeable allow more water
to seep inside
 Climate
Mechanical weathering occurs
faster in wet climates
Chemical weathering occurs
faster in hot temps
Weathering occurs more
rapidly in a warm rainy climate
The graph shows
the rate of
weathering for two
identical pieces of
limestone that
weathered in
different locations.
(1) What does the
x-axis of the graph
represent?
(2) What does the
y-axis of the graph
represent?
(3) How much
thickness did
Stone A lose in
1,000 years?
How much
thickness did
Stone B lose in
the same
period?
(4) Which stone
weathered at a
faster rate?
(5) Since the two
identical pieces of
limestone
weathered at
different rates, what
can you infer
caused the
difference in their
rates of
weathering?
 Soil is the loose weathered material
on the earth’s surface
 Main ingredient: bedrock
 Bedrock: solid layer
of rock beneath soil
 Rock particles
 Minerals
 Humus: dark colored substance
that is plant and animal matter
decay
 Water
 Air
 Fertility of Soil: measure of
how well the soil supports
plant growth
 Depends on size of
individual soil particles
Largest: Gravel
Sand
Silt
Clay
 Texture is important for plant growth
Clay holds too much water
Plants drown
Sandy soil drains quickly
Plants die from too little water
Loam: best type of soil for growing
plants
Soil that is made of equal parts of
sand and clay
What two
materials
make up the
major portion
of this soil?
 Soil forms as rock is broken
down by weathering and is
mixed with other materials
on the surface.
 Soil Horizon: a
layer of soil that
differs in color
and texture from
the layers above
and below it.
 Horizon A:
Topsoil which is
a crumbly dark
brown soil
mixture of
humus, clay,
other minerals
 Horizon B: clay
and other
particles
washed down
from horizon A
Also called
subsoil
 Horizon C
Only
weathered
rock
 Climate
Soil formation quickly forms
in a warm rainy climate
 Type of rock
Limestone forms soil more
quickly
 Climate
Thick soil: Moderate Temp
 Plants
Grassland soil is different from
forest soil
 Soil Composition
rocky
sandy
clay
 Make humus (formed from
decomposition)
 Litter: a loose layer of
dead plant leaves and
stems on the
surface of the soil.
 Decomposer: organisms that break
down the remains of organic
material
Bacteria
Worms
Fungus
Small animals
 Mix soil
 Makes space for
air and water
 Soil Conservation:
The management
of soil to prevent
its destruction
 Contour plowing farmers plow
their fields along the curves of
a slope.
 Conservation plowing: farmers
disturb the soil and its plant cover
as little as possible
 Crop rotation:
a farmer
plants different
crops in a field
each year.