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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.

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Onion skin weathering

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  1. Onion skinweathering 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

  2. The absence of clouds in tropical deserts & the overhead sun produces high day time temperatures Day Time The sun’s heat causes the outer layers of the rock to expand Most common in fine-grained rocks (e.g. volcanic rocks) & boulders

  3. RADIATION COOLING Different minerals expand and contract at different rates causing stresses along mineral boundaries. Quarts increases in size by three times more than feldspar With no clouds rocks cool quickly. A process known as radiation cooling Repeated daily heating & cooling causes outer layers of rock to be weathered Night Time Cooling causes the outer layers of the rock to contract Layers or shells of rock peel away Layers of rock collect on the desert floor

  4. 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? Onion skin weathering

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