what type of landslide has a very slow movement which is hardly noticeable?
What type of landslide has a very slow movement which is hardly noticeable?
Answer:
The type of landslide with a very slow movement, often imperceptible to the naked eye, is known as creep (also called soil creep). Unlike rapid mass-wasting events such as rockfalls or debris flows, creep operates on a timescale of months to years, gradually displacing soil or rock downslope.
Key Characteristics of Creep
- Slow Rate: Movement typically measures in millimeters or centimeters per year.
- Gravity-Driven: Occurs on slopes due to gravitational forces.
- Expansion & Contraction: Repeated cycles of freezing/thawing or wetting/drying can loosen particles, contributing to slow downslope movement.
- Hardly Noticeable: Structures such as fences, utility poles, or retaining walls might exhibit leaning or cracks over long periods.
Below is a concise table summarizing different types of landslides alongside their general movement speeds:
| Type of Landslide | Speed | Notable Characteristics |
|---|---|---|
| Rockfall | Very fast (meters/second) | Sudden detachment of rock from a steep slope |
| Debris Flow | Rapid (meters/minute to m/s) | Water-saturated flow of loose mud, soil, and rocks |
| Slump | Moderate (meters/hour to days) | Rotational slide with a concave slip surface |
| Earthflow | Slow to moderate | Flow of fine-grained materials, can continue for days or weeks |
| Creep (Soil Creep) | Very slow (mm/year) | Gradual downslope movement, often imperceptible |
For further reading, you can refer to the U.S. Geological Survey (USGS) or geology textbooks that discuss mass wasting and slope stability in detail.
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