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Contents of 11.5 How do geologic structures relate to stress, strain, and strength?

• Brittle faults and joints form in rocks close to the surface whereas plastic flow occurs at deeper levels where high pressure inhibits fracturing and temperature lowers rock strength.
• Compression shortens and thickens crust by producing folds, reverse faults, and thrust faults in shallow rock, and plastic flow in deeper rock.
• Tension elongates and thins crust by movement on normal faults in shallow rocks and taffy-like stretching of plastic rocks at deeper levels.
• Folds form by plastic flow in deep crust but also develop at and near the surface in sedimentary rocks where bending of thin layers and slippage along layers takes place.

11.5 How do geologic structures relate to stress, strain, and strength?