Transcript Onion skin weathering

Onion skin
weathering
Weathering is the physical, chemical and biological
breakdown of rocks in situ (same place).
Onion skin weathering is also known as:
•Exfoliation
•Thermal Expansion
•Insolation weathering
The absence
clouds in tropical deserts
Dayof Time
& the overhead sun produces high day
The sun’s heat
time temperatures
causes the outer
layers of the
rock to expand
Most common in finegrained rocks
(e.g. volcanic rocks)
& boulders
With no clouds Repeated daily heating &
Night
Time
rocks cool quickly.cooling
causes outer layers
A process known asof rock to be weathered
Cooling causes
radiation cooling
the outer layers
Different minerals
expand and contract
at different rates
causing stresses
along mineral
boundaries.
Quarts increases in
size by three times
more than feldspar
of the rock to
contract
Layers or
shells of rock
peel away
Layers of rock collect on the desert floor
Onion skin weathering
• Exfoliation is caused by alternate expansion &
contraction caused by temperature changes.
What happens in the day time?
(Dark rock can reach over 50oC)
What happens at night time?
• The outer layers of rock are exposed to extreme
temperatures (no vegetation or soil). Outer layers
of rock break away from the cooler inner layers.
Where can we find extreme temperature changes?