The Radium (British Columbia) and Miette (Alberta) hot springs occasionally produce "dirty" water that carries varying amounts of solid particles in suspension. Dirty-water events in the period 1959–1983 were caused either by heavy rains (or rapid snowmelt) or by earthquakes with magnitudes of 6.9 or greater, between 740 and 2300 km distant from the springs, in Alaska, Idaho, and Montana. Rainfall-induced events at Miette appear to require at least 34 mm of rain within a 48 h period. Associated decreases in water temperatures and dissolved-solids concentrations and changes in the ionic and isotopic compositions of the spring waters result from mixing of deep thermal water with cooler, less mineralized shallow water. By contrast, the earthquake-triggered events did not have significant thermal or geochemical effects. Suspended solids in the dirty waters represent surficial materials (including vegetation debris) and possibly residues from dissolution of carbonate rocks. At Miette Hot Springs the dirt contains secondary sulfur species (native sulfur and gypsum) derived from the HS− content of the spring water.