Changes that may occur in terrestric soils upon inundation with sea water are due mainly to microbial activity. Most prominant changes occur in the clay fraction, where conversion of clay minerals into smectites and/or micas may take place. Iron minerals from terrestric soils may be stable at the sea bottom, but in other cases pyrite and siderite may form. Organic matter will generally decrease in the topsoil of buried terrestric soils and may vanish completely.