What is weathering?
•
•
Weathering is the breakdown of rock material by physical and chemical processes.
Two kinds of weathering are physical weathering and chemical weathering.
What causes physical weathering?
• Physical weathering is the process by which rock is broken down into smaller pieces by
physical changes.
• The composition of the material does not change during physical weathering.
• Agents of physical weathering include temperature changes, pressure changes, plant and animal
actions, water, wind, and gravity.
• Changes in temperature can cause a rock to break apart by weakening the structure of the rock.
• Heat causes the rock to expand; cold causes it to contract.
• Ice wedging, or frost wedging, causes cracks in rocks to widen with repeated cycles of freezing
and thawing.
• How can a small crack in a rock eventually split the rock into two or more pieces?
• Rocks that formed under pressure deep within Earth can be exposed to the surface.
• As material is removed above the rock, the pressure decreases and the rock expands.
• Exfoliation is the process by which the outer layers of rock slowly peel away due to pressure
changes.
• Animals can cause physical weathering by digging burrows.
• New rocks, soils, and other materials become exposed at the surface as a result of animal
actions.
• Materials exposed at the surface are more likely to undergo weathering than those below.
• Abrasion is the breaking down and wearing away of rock material by the mechanical action of
other rocks.
• Three agents of physical weathering that can cause abrasion are moving water, wind, and
gravity.
• Rocks suspended in a glacier can also cause abrasion of other rocks on Earth’s surface.
• Roots of plants start out as tiny strands that may grow in small cracks in rocks.
• As the roots grow, they put more pressure on the rock, causing the rock to expand and
eventually break apart.
What causes chemical weathering?
• Chemical weathering is the breakdown of rocks by chemical reactions.
• Chemical weathering changes both the composition and appearance of rocks.
• Agents of chemical weathering include oxygen in the air and acids.
• Oxidation is the process by which chemicals in rock combine with oxygen in the air or in water.
• Rock surfaces sometimes change color, indicating that a chemical reaction may have occurred.
• Acids can cause chemical weathering by breaking down minerals faster than water alone.
• Acids in the atmosphere are created when chemicals combine with water in the air.
• Acid precipitation occurs when strong acids fall to Earth as rain, sleet, or snow.
• Acids in groundwater can cause rock to dissolve.
• A small crack in the rock can result in the formation of extensive cave systems carved out over
time.
• Rock material dissolved in groundwater can be carried and deposited in new locations over time.
• Acids produced by living things can cause chemical weathering.
• Chemical reactions occur as these acids move through tiny spaces in rock material.
• As the acids seep deeper, cracks form. Eventually, the rock can break apart.
What is weathering?
•
is the breakdown of rock material by physical and chemical
processes.
•
Two kinds of weathering are
weathering
and
weathering.
What causes physical weathering?
•
weathering is the process by which rock is
broken down into smaller pieces by physical changes.
•
The
•
Agents of
of the material does not change during physical weathering.
weathering include temperature changes,
pressure changes, plant and animal actions, water, wind, and gravity.
•
Changes in temperature can cause a rock to
apart
by weakening the structure of the rock.
•
Heat causes the rock to
•
Ice wedging, or frost wedging, causes cracks in rocks to widen with repeated cycles of
and
; cold causes it to
.
.
•
How can a small crack in a rock eventually split the rock into two or more pieces?
•
Rocks that formed under pressure deep within
can be
exposed to the surface.
•
As material is removed above the rock, the pressure
and the rock
expands.
•
is the process by which the outer layers of rock slowly peel
away due to pressure changes.
•
Animals can cause
•
New rocks, soils, and other materials become
result of animal actions.
•
Materials exposed at the surface are more likely to undergo
than those below.
by digging burrows.
at the surface as a
•
is the breaking down and wearing away of rock material by
the mechanical action of other rocks.
•
Three agents of physical weathering that can cause abrasion are moving
, and
•
,
.
Rocks suspended in a glacier can also cause
of other rocks on
Earth’s surface.
•
Roots of plants start out as tiny strands that may grow in small cracks in rocks.
•
As the roots grow, they put more pressure on the rock, causing the rock to expand and
break apart.
What causes chemical weathering?
•
weathering is the breakdown of rocks by chemical reactions.
•
Chemical weathering changes both the
•
Agents of chemical weathering include
•
and appearance of rocks.
in the air and acids.
is the process by which chemicals in rock combine with
oxygen in the air or in water.
•
Rock surfaces sometimes change color, indicating that a
reaction may have occurred.
•
Acids can cause chemical
by breaking down minerals faster than
water alone.
•
Acids in the
•
are created when chemicals combine with water in the air.
occurs when strong acids fall to Earth as rain, sleet, or snow.
•
Acids in
•
A small crack in the rock can result in the formation of extensive
can cause rock to dissolve.
systems carved out over time.
•
Rock material dissolved in groundwater can be carried and
in new locations over time.
•
Acids produced by
•
Chemical reactions occur as these acids move through tiny spaces in
things can cause chemical weathering.
material.
•
As the acids seep deeper,
form. Eventually, the rock can break apart.