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Weathering and Erosion
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HW 14-1 #1-7
1. wind, water, and temperature change
2. Water that seeps into cracks freezes and expands,
which widens and deepens crack with each
freeze/thaw cycle.
3. Plant roots grow and expand, physically wedging
rocks apart. Animal dig and burrow, which exposes
new rock to weathering.
4. Mechanical weathering is a physical process,
breaking large rocks into smaller rocks of the same
chemical composition. Chemical weathering
involves chemical reactions.
5. In oxidation, iron bearing minerals combine with
oxygen to form red colored iron oxide. In
hydrolysis, water and other substances in rock
react chemically to form two or more new
substances. In carbonation, carbonic acid converts
minerals into carbonates.
6. Oxidation, hydrolysis, and carbonation are all
chemical processes that weather rocks.
7. Acid precipitation forms when nitrogen oxides and
sulfur dioxide released during fossil fuel
combustion combine with water in the atmosphere
to produce nitric, nitrous or sulfuric acid. When
these acids fall back to earth they called acid
precipitation.
Weathering
• The breakdown of rocks on Earth’s crust into
smaller pieces.
Mechanical (Physical) Weathering
• Process by which rocks are broken down into
smaller pieces by external conditions.
• Types of Physical weathering
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Frost heaving and Frost wedging (ice)
Plant roots
Friction and impact
Burrowing of animals
Temperature changes
Frost Wedging
Frost Heaving
Plant Roots
Friction and Repeated Impact
Burrowing of Animals
Temperature Changes
Mechanical Exfoliation is the
peeling off of sheets of rock as they
expand and crack.
Chemical Weathering
• The process that breaks down rock through
chemical changes.
• The agents of chemical weathering
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Water (Dissolution)
Oxygen (Oxidation)
Carbon dioxide (Carbonation)
Living organisms
Acid rain
Water: Dissolution
• Water weathers rock by dissolving it
Oxygen: Oxidation
• Iron combines with
oxygen in the
presence of water in a
processes called
oxidation
• The product of
oxidation is rust
Carbon Dioxide
• CO2 dissolves in rain water and creates
carbonic acid
• Carbonic acid easily weathers limestone and
marble
Living Organisms
• Lichens that grow on rocks produce weak
acids that chemically weather rock
Acid Rain
• Compounds from burning coal, oil and gas
react chemically with water forming acids.
• Acid rain causes very rapid chemical
weathering
Chemical
Weathering
Karst Topography
• A type of landscape in rainy regions where
there is limestone near the surface,
characterized by caves, sinkholes, and
disappearing streams.
• Created by chemical weathering of limestone
Features of Karst: Sinkholes
Features of Karst: Caves
Features of Karst: Disappearing
Streams
Transport Agent of Forces
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Water
Wind
Ice (glaciers)
Gravity
Transport Agents - Water
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Rain
Streams and rivers
Ocean dynamics
Ice (glaciers)
Streams
Stream Erosion and Deposition
Glaciers
Wind Transport of Dust
More Wind Transport of Dust – West
Coast of Africa
Deposition Formation
Deposition Formation
Erosion
• The process by which water, ice, wind or
gravity moves fragments of rock and soil.
Water Erosion
• Rivers, streams, and runoff
Ice Erosion
• Glaciers
Wind Erosion
Mass Movements
• Landslides, mudslides, slump and creep
landslide clip.mpeg
Quiz Time –
List weathering, erosion, both or
neither
1.Waves are crashing on a sand
beach.
2.Water expands as it freezes in
the cracks of rocks.
3. Pebbles move down a stream
with the current.
4. Acid rain causes the
decomposition of a statue in New
York.
5. A Glacier slowly moves down a
mountain.
6. A tree’s roots grow into the
cracks of rocks.
7. A major volcano erupts
9. A shovel is left outside and
begins to rust.
1. As the sand is moving there is
definitely erosion; there is also
abrasion from the sand gains
colliding. Both
2. This is frost wedging so it’s
mechanical weathering. There is
no mention of movement.
Weathering
3. There is probably some
weathering, but there is
definitely erosion. Erosion or
Both
4. Acid rain on a statue is chemical
weathering. This is mainly
Weathering.
5. A glacier moving down a
mountain would have both
weathering and erosion. Both
6. A tree’s roots growing into
cracks of rocks would be
Weathering
7. Aweathering.
tree’s roots growing into cracks
of rocks would be weathering. Weathering
7. A major volcanic eruption
would involve both weathering
and erosion. Both
8. The rusting of a shovel is
oxidation. This is chemical
weathering. Weathering
14-2 Rates of Weathering
Vocabulary:
Differential Weathering
Surface area
Climate
topography
Weathering
• Is a SLOW destructive process.
• Carbonation weathers limestone onetwentieth of a cm (0.002) every 100 years.
1. Composition
• Differential Weathering: the process by
which softer, less weather resistant rocks
wear away at a faster rate than harder,
more weather resistant rocks do
• Sedimentary rocks (like limestone)
weather rapidly compared to other type
2. Amount of Exposure
• The more exposure to the weathering
agents: wind, water, gravity, the faster the
rock will weather.
• Surface Area: as rocks break into smaller
pieces the surface area increases
therefore weathering rate increases
3. Climate
• Alternating hot/cold climates tend to
weather faster because of the freezing and
thawing cycle, causing frost wedging a
form of mechanical weathering.
4. Topography
• The elevation and slope of the land
surface
– Temperatures are generally colder higher up
in elevation frost wedging is more evident.
– The steeper the slope, the more rocks pulled
downhill by gravity
5. Human Activities
• Mining, construction, recreational
activities, etc.
6. Plant and Animal Activities