Chunks Keep Regenerating After Being Replaced By Air

Earlier today I was going to build a new building, but ran out of land. To get more land, I replaced a section of a plains biome with air to get flat land. At first it looked like the picture below, but without the random chunks. Later on after clearing more land, I came back to find those chunks. I didn't think much of it and just replaced them with air again. I left for a little while and they regenerated. I can't continue building until this stops. Thanks a lot- Spencer