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Unformatted text preview: Prof. M. Fall - University of Ottawa 23 Decompression - Exfoliation of a plutonic rock Physical weathering Mechanical exfoliation of a plutonic igneous mass occurs after removal of overlying rocks allows it to expand upward, fracturing into thin slabs of rock parallel to its exposed surface Exfoliation: example Physical weathering Action of freezing (frost wedging) 4.1 Weathering of materials Water expands when it freezes, breaking rocks into angular fragments. The sandstone cliff of the canyon Bryce (Utah) undergoes an intense mechanical disintegration. For 8 months of the year, the average temperature is lower than 0°C the night and higher than 0°C the day. Which role that does it play in disintegration? Question Physical weathering Chemical weathering Decomposition and decay of the constituent Decomposition and decay of the constituent minerals in rock through chemical alteration of minerals in rock through chemical alteration of those minerals. Water is essential, with rates those minerals. Water is essential, with rates those minerals....
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- Spring '11