Assignment # 2 Weathering part 2
LO: I can determine if a landscape was chemically or mechanically weathered.
EQ: How can we use a model to differentiate between weathering, erosion and deposition?
Agenda
Notes
Activity
Discussion
HOMEWORK
Study today’s notes
Catalyst
Compare and contrast
weathering and erosion
WEATHERING – the breakdown of rocks into smaller pieces, called sediments.
• Mechanical- breaking down without changing its composition
• Chemical- processes that change the chemical composition of rocks and
minerals
EROSION – the process where the sediments are transported by wind, gravity,
glaciers, and running water.
DEPOSITION – the process whereby these sediments are dropped by their
transporting agents.
• Weathering: the process by which rocks break down and change
• Two types of weathering: mechanical and chemical
• Mechanical Weathering: the process by which rocks and minerals
break down into smaller pieces, does not change the rock’s
composition
• Mechanical weathering comes from:
• Temperature changes: when water freezes, it expands. Ice takes up more
room than water
• Frost wedging: thawing and freezing of water in the cracks of rocks is called frost
wedging
• Exfoliation: outer layers of rock are stripped away
• Composition: what something is made of
• Chemical Weathering: rocks and minerals change in their composition
because of chemical reactions (rust)
• Things that cause chemical weathering:
• Oxygen, acid, water
• Chemical reactions between rocks and water form new minerals
• Some minerals, like calcite, dissolve completely
• Higher temperature can make reactions go faster
• Composition – what something is made of
• Water: dissolves many minerals and rocks
• Oxygen: oxygen can combine with other substances by oxidation
Iron + oxygen -> RUST
• Carbon dioxide: carbon dioxide combines with water to make an
acid, this can dissolve rocks and minerals
carbon dioxide (CO2) + water -> carbonic acid
Glaciers
• Glaciers are large masses of
ice and snow
• Takes can take 100,000 years
to form a glacier
• Move 2.5 cm a day
Glaciers
• 2 types of glaciers
• Valley glaciers – form in stream
valleys
• Continental glaciers – very thick and
cover land (Antarctica and
Greenland)
• Glaciers erode land as they pass
over them
• As glaciers melt, they deposit
sediment
Wind
• Wind lifts and deposits loose
material
• Wind also can weather rocks
• Erosion is moving weathered material from one location to another
• Erosion is caused by running water, rain, waves, glaciers, wind, and
gravity (landslides)
• Deposition – when sediments are laid down in a new location by a
process of erosion
erosion
• Normal erosion takes a long time but a landslide is a fast form of
erosion
Landslide in Southern
California on June 1,
2005
Mass wasting
• Creep – slow mass
wasting when ground
moves slowly
downhill
SKITTLES LAB (do not write)
10 drops
VISUAL
WRITTEN
20 drops
30 drops
40 drops
50 drops
Work together with your group to answer the questions. (Use Spit Back
format)
1. When did mechanical weathering occur during this lab activity?
2. When did chemical weathering occur during this lab activity?
3. When did erosion take place during this lab activity?
4. What did the water represent in this lab activity?
5. What did the Skittle represent in this lab activity?
6. What did the color on the Skittle represent in this lab activity?
7. What did the tin pan represent in this lab activity?
8. From where we left off, could your group demonstrate deposition? How?
1. When did mechanical weathering occur during this lab activity?
When the precipitation from the water dropper hit the Skittle and pieces of the
shell were worn away or broken off (including the letter S)
2. When did chemical weathering occur during this lab activity?
When the Skittle sat in the water that accumulated on the surface of the Earth
(tin pan) and the color (minerals, rock fragments, sediment) dissolved off of the
bottom of the Skittle
3. When did erosion take place during this lab activity?
When the colored water flowed away from the Skittle-the water was carrying
away the color (minerals, rock fragments, sediment)
4. What did the water represent in this lab activity?
Precipitation/rain that weathered the Skittle
5. What did the Skittle represent in this lab activity?
A rock
6. What did the color on the Skittle represent in this lab activity?
Minerals, rock fragments, sediment
7. What did the tin pan represent in this lab activity?
The surface of the Earth
8. From where we left off, could your group demonstrate deposition? How?
Possible answer: Pour the water from each tin pan through a stack of paper
towels. The water will soak through and leave behind anything that was
carried away by the water including the color (minerals, rock fragments,
sediment)
Part 1: Glue the three images to your notebook AND for each
write:
What type of weathering created the formation and how can
you tell.
Part 2: Write a story about something that got weathered,
eroded, and deposited.