Sag pond
A sag pond is a body of water collected in the lowest parts of a depression formed either near the head scarp of rotational landslides[1] or between two strands of an active strike-slip fault.[2] Sag ponds may be useful identification features in aerial photographs for mapping faults and landslides.
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Rotational landslides [edit]
Deep-seated landslides may exhibit rotational failure along a curved slip surface resembling a circular arc in a vertical cross-section along the axis of soil movement. Rotational failure occurs when a bowl-shaped block of soil rotates to reduce the slope of the ground surface. The uphill edge of undisturbed soil surrounding the bowl may be left exposed as a steep scarp face indicating the uphill boundary of the landslide. The lower edge of the rotating bowl tends to break apart and collapse into translational downhill movement. A sag pond may form below the head scarp if rotational momentum carries the ground surface of the rotating soil block past horizontal.[3]
Fault lines [edit]
The relative motion of the two fault strands results in a stretching of the land between them, causing the land between them to sink.
External links [edit]
Sources [edit]
- ^ "Earthquake Images". Idaho Geological Survey. Retrieved 2013-02-10.
- ^ Nevada-Government Dictionary on Water Words, retrieved April, 3rd 2012
- ^ Samford, Jerrold "Narrows Landslide, Giles County, Virginia" in Virginia Minerals volume 29, number 4 (November 1983) p.37
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