Weathering is the physical, chemical and biological
breakdown of rocks in situ (same place).
Onion skin weathering is also known as:
The absence of Time in tropical deserts
& the overhead sun produces high day
The sun’s heat
causes the outer
layers of the
rock to expand
Most common in fine-
(e.g. volcanic rocks)
With no clouds Repeated daily heating &
rocks cool quickly. cooling causes outer layers
A process known as rock to be weathered
of Cooling causes
radiation cooling the outer layers
Different minerals of the rock to
expand and contract contract
at different rates Layers or
causing stresses shells of rock
along mineral Quarts increases in
boundaries. size by three times
more than feldspar
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?