Transcript Chapter 2 Weathering and Soil Soil

Chapter 2 Weathering and Soil
Mechanical Weathering
Mechanical weathering affects all rock on Earth’s surface.
Release of Pressure As rock erodes, release of pressure
causes the outside of the rock to crack and flake off.
Freezing and Thawing When water freezes in a crack in a
rock, it expands and makes the crack bigger.
Animal Actions Burrowing animals like this mole can
loosen and break apart rocks and soil.
Plant Growth Roots of plants enter cracks in rocks, forcing
the cracks farther apart.
Abrasion Rock particles carried by wind, water, or ice and
wear away exposed rock surfaces like sandpaper on wood.
Chapter 2 Weathering and Soil
Chemical Weathering
WATER (H2O) Water dissolves rock. I can also mix with other
chemicals to dissolve rock quicker.
OXYGEN (O2) Combines with iron to cause rust
CARBON DIOXIDE (CO2)
Combines with water to cause
Type of acid rain
LIVING ORGANISMS
Grow in cracks in rock and cause
additional cracking. Some roots produce weak acids
ACID RAIN
Air pollution mixes with water to form sulfur, nitrogen
and carbon compounds that cause rapid chemical weathering
Chapter 2 Weathering and Soil
Chemical Weathering
As weathering breaks apart rock, the surface
area exposed to weathering increases.
Chapter 2 Weathering and Soil
Chemical or Mechanical?
Reddish soil
Chemical
Rock in a desert
breaking because of
repeated heating and
cooling
Mechanical
Ants making large
hills
Mechanical
Chapter 2 Weathering and Soil
Rate of Weathering
The most important factors that determine the
rate at which weathering occurs are the type of
rock and the climate.
Some rocks weather more easily because they
are permeable, which means filled with tiny
connected air spaces.
Define “permeable” in your notebook, include
examples
Chapter 2 Weathering and Soil
Which Weathered Faster?
The graph shows the rate of
weathering for two identical
pieces of limestone that
weathered in different locations.
Chapter 2 Weathering and Soil
Which Weathered Faster?
Reading Graphs:
What does the x-axis of the
graph represent?
Time in years
Chapter 2 Weathering and Soil
Which Weathered Faster?
Reading Graphs:
What does the y-axis of the
graph represent?
The thickness of stone lost to
weathering
Chapter 2 Weathering and Soil
Which Weathered Faster?
Reading Graphs:
How much thickness did
Stone A lose in 1,000 years?
How much thickness did
Stone B lose in the same
period?
Stone A lost about 8.5
millimeters; Stone B lost
slightly more than 4
millimeters.
Chapter 2 Weathering and Soil
Which Weathered Faster?
Drawing Conclusions:
Which stone weathered at a
faster rate?
Stone A weathered at a faster
rate.
Chapter 2 Weathering and Soil
Which Weathered Faster?
Inferring:
Since the two identical
pieces of limestone
weathered at different rates,
what can you infer caused the
difference in their rates of
weathering?
They were exposed to
different climate conditions.
Chapter 2 Weathering and Soil
Soil
Loam, a type of soil, is made
up of air, water, and organic
matter as well as materials
from weathered rock.
How is the high percentage of
air and water related to the
amount of organic matter in
the loam?
Organic matter helps create
space for air and water.
Chapter 2 Weathering and Soil
Soil
Soil particles range in size from gravel to clay particles too
small to be seen by the unaided eye. The sand, silt, and clay
shown here have been enlarged.
Chapter 2 Weathering and Soil
The Process of Soil Formation
Soil forms as rock is broken down by weathering and mixes
with other materials on the surface. Soil is constantly being
formed wherever bedrock is exposed.
Chapter 2 Weathering and Soil
The Process of Soil Formation
Which soil horizon is most similar to bedrock?
Which soil horizon forms last?
Which is most important for growing food?
C
B
A
Chapter 2 Weathering and Soil
Living Organisms in Soil
Some soil organisms make humus, the material that makes
soil fertile. Other soil organisms mix the soil and make
spaces in it for air and water.
Chapter 2 Weathering and Soil
Soil Damage and- Loss
Wind erosion is one cause of soil
loss. For example, wind erosion
contributed to the Dust Bowl on the
Great Plains. The Dust Bowl ruined
farmland in western Oklahoma and
parts of the surrounding states.
Wind blew dry particles of soil into
great clouds of dust that traveled
thousands of kilometers.