subsidence

noun2

1. •
   A sinking of something to a lower level, especially of part of the surface of the Earth due to underground excavation, seismic activity or underground or ground water depletion, or the rocks in a geological basin, due to continued deposition from above.

   • In the early hours of April 28, 1953, it was completely blocked by a subsidence, which caused the death of five persons, when a pair of semi-detached houses collapsed into the cavity. — 1957
2. •
   The process of becoming less active or severe.

   • The subdual or subsidence of the more violent passions. — 1754