Transcript Weathering and Soil Formation

Weathering and Soil Formation
The Effects of Weathering
1. Weathering is the process that
breaks down rock and other
substances on Earth's surface.
2. What contributes to weathering?
• Heat
• Cold
• Water
• Ice
The Effects of Weathering
• Forces of weathering break rock into
smaller pieces.
–Erosion carries the pieces away.
3.Erosion is the movement of rock particles
by wind, water, ice, or gravity
4.There are two kinds of weathering:
• Mechanical weathering
• Chemical weathering
Mechanical Weathering
5. Weathering where rock is physically broken into
smaller pieces is called mechanical weathering.
– smaller pieces have the same composition as the original
rock
6. Mechanical weathering breaks rock by
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Freezing and thawing (Ice wedging)
Pressure
Growth of plants
Actions of animals
Abrasion
7. Abrasion is the grinding away of rock, by rock
particles carried by water, ice, wind, or gravity.
Mechanical Weathering
Chemical Weathering
8. Chemical weathering is the process that
breaks down rock through chemical
changes.
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The agents of chemical weathering include:
Water
Oxygen
Carbon dioxide
Living organisms
Acid precipitation (acid rain)
10.Chemical weathering produces rock
particles that have a different mineral
makeup from the rock they came from.
Chemical Weathering
Chemical and Mechanical Weathering
• Chemical and mechanical weathering
often work together.
11. As mechanical weathering breaks rock
into pieces, more surface area becomes
exposed to chemical weathering.
Water and weathering
• How does water contribute to weathering?
12. Water is the most important agent of chemical
weathering.
– Water weathers rock by dissolving it.
– Over time, many rocks will dissolve in water.
Water and weathering
13. Water can also freeze, expand in
rock and break it apart. (Ice wedging)
Oxygen
• How does oxygen contribute to weathering?
• The oxygen in the air is an important cause
of chemical weathering.
– Think of a Bicycle or metal tool left outside in
the rain
14.Iron combines with oxygen in the presence
of water in a process called oxidation.
15.The product of oxidation is rust.
• Rust makes rock and metal soft and crumbly
Oxygen
Living Organisms
• How do living organisms contribute to weathering?
• Weak acids around the roots slowly dissolve rock
chemically.
Acid Rain
• How does acid rain contribute to weathering?
• Over the past 150 years, people have been
burning large amounts of fossil fuels (coal,
oil, and gas) for energy.
• Burning these fuels can pollute the air.
• These fuels react chemically with the water
vapor in clouds, forming acids.
• These acids mix with raindrops and fall as
acid rain.
• Acid rain causes very rapid chemical
weathering like the picture seen before…..
Chemical Weathering
Rate of Weathering
16.The most important factors that
determine the rate at which weathering
occurs are
• Type of rock
– Sedimentary, Igneous, Metamorphic
• Climate
Permeable Rocks
• Some rock weathers easily because it is permeable.
17.Permeable means that a material is full of tiny,
connected air spaces that allow water to seep
through it.
• Permeable rock weathers chemically at a fast rate
Climate
• How does climate contribute to
weathering?
• Climate refers to the average weather
conditions in an area.
– It’s not the same thing as weather.
• Both chemical and mechanical
weathering occur faster in wet climates.
18.Chemical reactions occur faster at
higher temperatures.
Climate and Weathering