I can say for sure groundhogs do pull up targets lol. Found some nails and old lead that one retrieved pushing dirt out of a hole once a long time ago.Let's not forget the ever busy Moles.
Those pesky coins get in the way.
And they'll just push them up and outta their way
Thats what the hobby is about. I can say this as long as its making you happy or doing what you want it to do, you've got the right detector. Detecting attracts all types, from people looking for a relaxing hobby, to people looking to darn near make a living off it with the stuff they find.Joe and Jim use something in a price range they can afford or are just starting out in the hobby. Looks like fun and want to see if they like it. Some others are swinging the newest technology out regardless of cost.
I see alot of soil erosion from flooding and water. Any time after it rains and floods, i head out to my creek and river spots. and hit the fields. On an additional note. I have always seemed to do better when the ground is wet, or has just rained. I think there is some research/people that have concluded that you do get better vdis-depth in wet ground, but i can;t remember where i saw thatThe soil is dynamic,not static.There are many factors that cause the soil to constantly shift,moving objects that are contained within it.Like you i have found objects on the surface that should be deep and deep objects you think would be shallow.Frost has s major influence on soil......as moisture in soil freezes it expands and causes quite substantial movement.Biological processes also cause movement......worms,microbes,decay etc all contribute to the constant movement of soil.Wind erosion can also play a major part removing a lot of top soil if it becomes very dry and dusty.