slickenside
/ˈslɪkənˌsaɪd/
noun
- A polished, grooved surface on a rock, caused by friction during an earthquake or movement along a fault line.
- The geologist pointed to the shiny slickenside on the cliff face, evidence of ancient fault movement.
- The museum displayed a large slab of rock with a slickenside, showing the direction of the prehistoric earthquake.
- Hikers sometimes mistake a slickenside for a natural mirror because of its smooth, reflective surface.