Download Aim: Weathering - Hicksville Public Schools

Aim: Weathering
What are the different types of
processes that break down
rocks?
• The breakdown of rocks and other
materials on the Earth’s surface
• It is a slow and continuous process that
affects all substances exposed to the
atmosphere
Two types of weathering:
1. Physical
• Occurs when rocks are broken down
into smaller pieces called sediments
• There is no change in composition
Agents of Physical Weathering:
•
•
•
•
Frost Action
Abrasion
Exfoliation
Root Pry (Root Wedging)
Frost Action
When water
repeatedly freezes
and thaws in a small
crack in a rock it will
expand and force
the rock apart
Abrasion
• The wearing down of rocks when they
are rubbed against each other as they
are carried by rivers and ice
• Occurs mainly dry areas
Here, the photo shows some pits that have
been eroded into the rock by sandblasting
The powerful effect of wind generated
abrasion (Double Arch from Arches
National Park)
Exfoliation
• The peeling away of large sheets of loosened
material at the surface of a rock
Root Pry
• Roots from plants
grow into cracks in
rocks searching for
nutrients and cause
the rock to break
apart
2. Chemical Weathering
• Changes in the mineral composition or
chemical makeup of a rock
• Minerals can be added, removed or
broken down
Hydration
• When water unites with certain minerals
such as feldspar and they crumble into
small particles of clay
Oxidation
• When oxygen combines with iron to form iron
oxide (rust)
Carbonation
• Carbon dioxide
dissolves in water to
form carbonic acid
• Dissolves large
amounts of
limestone
Organic Decay
• The decay of plants produces acids
which dissolve minerals causing rocks to
break down
• Much like carbonation