I've just purchased an 80 yr old house which has about a 2 inch gap between the foundation, and the yard on one side. It seems to be fairly deep at around 4 feet. I can certainly get some crushed gravel and backfill it, and then top off with some soil, but am just wondering if anyone knows what could have caused this in the first place. There are no signs of water leaking inside, or cracks from shifting, etc (basement walls are not covered). Also there are no trees/plants in the area as well.