Glue this side
into your
Science Journal
WEATHERING
Weathering - The processes at or near Earth’s surface that
cause rocks and minerals to break down by air, water, plants
and animals.
2 Types of Weathering
 Mechanical/Physical Weathering
 Chemical Weathering
Mechanical/Physical Weathering - A rock is physically
changed without a change in chemical composition
• Frost Action / Ice Wedging - Alternating freezing and
thawing of water causes material to break up.
• Abrasion - Wearing down or smoothing of a material
due to constant collisions by wind and water.
• Plant and Animal Action - Plant root growth and
animals burrowing increase the exposure of rocks to
the air and water and causes breakdown.
• Thermal Expansion and Contraction - Extreme
changes in temperature causes cracking.
• Pressure Unloading / Exfoliation - Earth’s forces can
push rock that formed deep underground up to the
surface. The pressure causes the rock to expand and
crack. This leads to exfoliation.
Chemical Weathering - Processes that change the
chemical composition of rocks and minerals
• Hydrolysis - Water is very slow reaction and the main
cause of chemical weathering.
• Oxidation - Where Oxygen combines with other
substances to produce rust
• Acid Reactions / Carbonation - Carbon reacts with
other substances to dissolve and alter the chemical
makeup of rocks forming caves. Nitric acid produced
by the decay of organic material can alter soil
composition
Differential Weathering - The variable rate of which rocks
weather is called differential weathering. Most weathering
occurs over long periods of time- hundreds, thousands, or
even millions of years.
Factors affecting the rate of weathering
Rocks weather at different rates due to
differences in
mineral composition. The harder the rock, the slower the
rate of weathering is.
 Composition (granite vs. limestone) What minerals a
rock is made from
 Climate (hot, wet, cold, dry) hot, wet regions weather
rocks faster than cold, dry ones
 Rock size (surface area) How large or small a rock’s
surface is
Climates
Cold Climates – Mechanical weathering breaks down rocks
rapidly
Warm, Wet Climates – Chemical weathering breaks down
rocks rapidly.
EROSION
Erosion - The process of removing Earth materials from
their original sites through weathering and transport agents
or forces
Transport Agents or Forces
 Water (Rain, streams, rivers, oceans, and ice/glaciers)
 Wind
 Gravity
DEPOSITION
Deposition - The process by which water, ice, wind, and
gravity drop newly formed sediments.
Deposition Formations
 Delta – a fan-shaped pattern formed as rivers deposit
their load in a body of water
 Alluvial Fan – a fan-shaped deposit that forms on dry
land.