Warm Up Tuesday, Nov. 4
1. Define mechanical weathering. Define
chemical weathering.
2. What do you think causes weathering to
happen faster?
Rates of Weathering
• What is differential
weathering?
• How does surface area
affect the rate of
weathering?
• How does climate affect the
rate of weathering?
• Why do mountaintops
weather faster than rocks at
sea level?
What Factors Affect the Rate of
Weathering?
• 1. make up of rock
(composition)
• 2. surface area
• 3. climate
4. elevation
What can effect the
rate of weathering?
#1 Make-up
(composition) of Rock
Differential Weathering
• Softer rocks whether more quickly than
harder rocks.
• Differential weathering is a process by
which softer, less weather-resistant rocks
wear away and leave harder, more
weather-resistant rocks behind.
Example of Differential
Weathering: Devils Tower
Devils Tower
appears as it
does today
because of
differential
weathering. As
surrounding rock
was worn away,
the hard rock of
the tower was
exposed.
On Your Rates of Weathering
Question WS
Answer Questions #1-3
What can effect the
rate of weathering?
#2 Surface Area
#2 Surface Area
• Weathering takes place on the
outer surface of rocks.
#2 Surface Area
• If a large rock is broken into
smaller pieces, weathering of the
rock happens much faster.
• Explain:
– This is because the broken pieces
expose more of the rock to
weathering.
–Multiple pieces of one rock will have
a greater amount of surface area
for the same amount of volume.
Surface area. If these all contain the same
volume of rock, which one will weather faster?
Total Surface Area to Volume
On Your Rates of Weathering
Question WS
Answer Questions #4-5
What can effect the
rate of weathering?
#3 Climate
#3 Climate
• Climate: overall temperature and
weather of a region over a long
period of time.
#3 Climate- 2 ways climate speeds
up weathering.
1. Chemical weathering:
Will happen faster in warm, humid
(moist) climates than in cold, dry
climates.
#3 Climate- 2 ways climate causes
weathering.
How does climate speed up
chemical weathering?
Explain: Warmth and moisture will
speed up the process of oxidation
(rusting), thus weathering happens
faster.
Climate- 2 ways climate speeds up weathering
2. Mechanical weathering- Ice and
temperatures changes.
Climate- 2 ways climate speeds up weathering
Explain:
• When water gets into the crack of rock
and freezes, it expands, pushing the
rock apart.
• Warmer temperatures thaw (melt) ice.
• Freezing temperatures freeze the
water, expand, and push the rock apart
further
• Freeze-thaw(melt)-freeze-thaw(melt):
pattern that causes ice wedging.
On Your Rates of Weathering
Question WS
Answer Questions #6-9
What can effect the
rate of weathering?
#4 Elevation
#4 Elevation- Exposure
• Higher elevation=
more weathering.
• Low elevation= less
weathering.
#4 Elevation
Explain:
• Higher elevations (mtn tops) are exposed
to more wind, rain, and ice than rocks at
sea level or lower elevations.
• The increase of these agents causes more
mechanical and chemical weathering.
Question:
• Why will mountain tops whether away faster
than rocks at a lower elevation?
#4 Elevation- Gravity
Gravity
• Gravity affects the rate of weathering:
– 1. Steepness of mountain slope: when it
rains, water runs off steep mountain slopes
more quickly, carrying sediment away.
– 2. When sediment is carried away, it exposes
new to rock to weathering.
– 3. Abrasion As rocks tumble down mountain
side, the hit each other, breaking them apart
more and increasing the surface area of rock
that will be exposed to more weathering.
Weathering
and Elevation
The Ice, Rain,
and Wind that
these mountain
peaks are
exposed to
cause them the
weather at a
fast rate.
On Your Rates of Weathering
Question WS
Answer Questions #10-15
Let’s Sum it Up
• Now….Let’s see what
you learned!
Get out notebook paper,
number the paper 1-11.
Let’s Sum it Up
1. _________rocks weather more slowly than
softer rocks. (hard; soft)
2. The more surface area of a rock that is exposed
to weathering, the ________ the rock will be worn
down. (faster; slower)
3. Chemical weathering occurs _________ in
warm, humid climates. (faster; slower)
4. Weathering occurs faster at ______ elevations
because of an increase in ice, rain, and wind.
(high; low)
Quick Check
5. What four factors determine the rate at
which rock weathers?
1.
2.
3.
4.
Quick Check
6. The process by which softer, less weather
resistant rocks wear away and leave
harder, more weather-resistant rocks
behind is called
A.
B.
C.
D.
mechanical weathering
chemical weathering
differential weathering
acid precipitation
Quick Check
7. Weathering takes place
A. on the outer surface of rocks.
B. on all rocks equally.
C. inside the rocks.
Quick Check
8. Because of a large rock’s volume, it will
A.
B.
C.
D.
weather unevenly.
weather relatively quickly.
not weather at all.
weather relatively slowly.
Quick Check
9. What is the average weather condition in
an area over a long period of time called?
_______________
Quick Check
10. Chemical weathering such as oxidation
occurs more quickly in a climate that is
___________ and ________________.
1.
2.
Quick Check
11. Weathering occurs faster at high
elevations because of
A.
B.
C.
D.
an increase in wind but not ice or rain.
an increase in ice and rain but not wind.
a decrease in wind, ice, and rain.
an increase in wind, ice, and rain.