For the past year or so, when I go to mow my lawn there have been big piles of dirt appearing in my yard. I have excavated them and there are no holes or disturbances around them just grass, as if the dirt has just been piled there. I have seen from others that it might be moles or gophers but I am starting to doubt this seeing that these mounds are quite larger then the ones I have seen in pictures. also were they appear frequently (in my back yard) the soil is quite dark but the foundation and front yard of my house has red soil, so the soil does not even match so its not like its being dug up from that area. Its not a big deal I am just worried the dirt might dull my mower blades and its just a little weird.