Download Weathering and The Rock Cycle

Weathering and The Rock
Cycle
Weathering
• Weathering is the breaking down of rocks
into sediments. After the rocks have been
broken other forces carry the rocks away.
• Weathering affects rocks, caves, mountain
and even buildings and streets. Different
types of weathering (chemical and
mechanical) break down earth’s surface
and have changed what we see over
billions of years. Mountains becomes hills.
Mechanical Weathering
• Mechanical weathering occurs when rocks are
broken apart by physical processes.
– The rocks actually disintegrate but the overall
chemical make-up of the rock stays the same. Each
piece of rock is similar to the original rock. It is like a
jackhammer smashing up rock.
– Growing plants, burrowing animals, and expanding
ice can mechanically weather rocks. Enough force is
created to break the rocks into smaller pieces.
The Major Types of Mechanical
Weathering are:
• 1.) Frost Wedging
• 2.) Exfoliation/ Uploading
• 3.) Organic Activity
Mechanical Weathering – Frost
Wedging
• When water enters the cracks in a rock
and freezes, it expands.
• The cracks enlarge and the rock breaks
apart.
• Then more water can enter the crack,
freeze and expand, causing the cracks to
grow bigger. This processes also breaks
up roads
Freeze Thaw Cycle
Freeze Thaw Cycle
Mechanical Weathering Exfoliation
• The rock weathers and erodes away
• There is less weight and pressure pushing
down on the rock
• The rock expands upward under reduced
pressure and breaks into sheets and
slabs.
Mechanical Weathering - Organic
• Water and nutrients that collect in the
cracks of a rock allow plants to grow.
• Plant roots grow into rocks and split it
apart
• Burrowing animals, such as earthworms
and moles can loosen sediments.
Mechanical Weathering
• Once a rock weathers, its surface area
increases, thus the surface area exposed
allows for more weathering
Chemical Weathering
• Chemical Weathering occurs when
chemical changes dissolve the minerals in
rocks or change the minerals into different
minerals.
• Occurs when rocks react with air, water
and other chemicals.
• 2 major types of chemical weathering:
– Oxidation
– Acid reactions
Chemical Weathering - Oxidation
• When rocks containing iron are exposed to
air and water
• The rocks oxidize or “rust” producing a red
colour
– A rusty nail or bike chain
Chemical Weathering – Acid
Reactions
• When water reacts with carbon dioxide it
produces carbonic acid.
• The acid reacts with the rocks that contain
calcite (Limestone)
• Rocks like Limestone will dissolve from the
acid.
Factors affecting Weathering
• 2 Major factors affecting weathering are:
– Mineral Composition of Rock
• Some minerals are less stable and dissolve faster
than others
– Climate of a region
• The warmer and more wet a region is, the more
weathering occurs
• Climate affects both mechanical and chemical
weathering
Rock Cycle
• Rocks can be broken apart, chemically
altered, dissolved and carried away by
water and ice. Once the rock reaches a
new location, it can undergo even more
changes and become part of an entirely
different family of rocks. Sedimentary
rocks can become metamorphic rocks.
Metamorphic rocks can become igneous
rocks.
Rock Cycle
• The ROCK CYCLE consists of the
processes in which rocks are continually
changed over long periods of time.
How the Rock Cycle Works
• Many foods are made by the same processes
that rocks undergo in the rock cycle.
• How is chocolate fudge like an igneous rock?
(heating and cooling)
• How is a granola bar like a sedimentary rock?
(different types of sediments cemented together)
• How is a grilled cheese sandwich like a
metamorphic rock? (how heat transforms the
cheese)
Bonus Activity
• Complete a diagram and write-up with
your class a food you could use to
represent processes in the rock cycle.
Explain the similarities between rocks and
your food. Discuss what steps of the food
preparation represent processes in the
rock cycle.