weatheri ng weathering is the physical and chemical breakdown of rocks at the earth’s surface. the...
TRANSCRIPT
Weathering
Weathering is the physical and chemical breakdown of rocks at the Earth’s surface.
The pieces or particles of rock (large and small) that
are weathered are known as sediments.
Weathering occurs when
rock is exposed to “weather events” (ex: wind, water,
pressure changes), as well as, the actions of organisms.
Chemical Weathering is the breakdown of rock through a change in the composition of
the rock..
The red color in this rock represents chemical weathering. The original composition of the rock has changed due to its exposure to rain. The iron
minerals in the rock combined with the oxygen molecules in rain water to create iron oxide (rust).
The iron oxide in the rock can weather easily.
The statue has gone through chemical weathering. Water combines with carbon dioxide in the air to create carbonic acid.
Carbonic acid will dissolve specific minerals, such as those found in limestone
or marble.
Physical (Mechanical) Weathering is the breakdown of
rock into sediments without chemically altering the rock. .
Frost Action: Water will make its way into a crack in the rock When the water freezes, it will expand widening the crack in the rock.
Frost action is responsible for damage done to roadways.
Abrasion: A form of physical weathering whereby rock particles grind against other rock particles.
An agent of erosion such as gravity, running water, wind, glaciers and/or tides are responsible
for abrasion.
Physical Weathering
In this example, the wind pushes small sediments against larger ones. This
leads to abrasion.
“How does abrasion work?”
Sometimes the weathering of rocks can be caused by biologic action.
Living organisms can weather rocks both chemically and physically.
Some organisms will release compounds
through biologic activity. These compounds will chemically breakdown
rocks.
The roots of plants will grow into cracks found in rocks. The growth of these roots physically
breakdown rocks.
Biologic Action
Factors that Impact Weathering Exposure The closer a
rock is to Earth’s surface, the faster it will
weather.
The exposed bedrock along the beach will weather quickly due
to:1. changes in
temperature2. exposure to wind
and precipitation3. exposure to
chemicals that can alter rock
4. tidal action
Factors that Impact Weathering
Particle Size and Mineral Composition
Smaller sediments have a larger surface area exposed to
weathering agents and will weather more quickly than
larger sediments.
Some minerals in rocks are more resistant to weathering
than other minerals.
The minerals that make up this vein of granite are more resistant to weathering than the dark parent rock surrounding it.
Factors that Impact Weathering Climate
Specific types of weathering and its intensity are prone to
certain climates.
PHYSICAL WEATHERING: Prone to climates that are
cool and dry.
CHEMICAL WEATHERING:Prone to climates that are
warm and humid.
Soil Formation Soil is a combination of organic (living) and inorganic (nonliving) matter that
accumulates at the Earth’s surface.
Sediments that have weathered from rocks become part of the soil.
Soil from parent bedrock can form
in horizontal layers over time. The upper layers
contain more organic material than the lower
layers.
Many soils are transported by water, wind or glaciers to new locations.
The soil may then become the parent material for new soils to form.