Chip seal is when a layer of oil is placed on top of the existing paved road and gravel is applied to the top. After a couple of days, you get a new surface repairing small issues that were on the old road. Not all the gravel sticks (and our county is particularly good at putting too much gravel everywhere) so excess gravel can pile up places.

I'm on a mountain bike and have 2" tires on at the moment. I don't think much of anything would have helped hitting 3" deep gravel while turning especially if it looks like asphalt.