原级：depression
1. Karst depressions are usually located in regions plentiful in limestone and dolomite, where groundwater has enlarged openings to form a subsurface drainage system.
2. Deep depressions marked the site, and I was told this was where gunpowder was produced.
3. Cyclones often turn into rain depressions which bring substantial falls that can lead to prolonged flooding.
4. Fortunately, this recipe for creating future European depressions was rapidly dropped.