sentences:  Meanwhile, a subsidence problem that had irreparably damaged at least 10 downtown buildings by 1928 worsened through the 1930s.Dozens of buildings, including the post office and jail, were lost as the earth beneath them sank away.Contributing causes were geologic faulting in the area, blast vibrations from the mines, and erosion that may have been exacerbated by vegetation-killing smelter smoke.