Very nice Deepbeeps. And you are right, no place is EVER hunted out totally. I go back to places I have hunted, and still find stuff right where I was not too long ago. Hit it at a different angle and you would be amazed at the new targets you get.
I second that Hoser....hitting a lot from different directions will almost always produce something that was missed. We have frost heaves here every winter, so with the ground moving so much you're almost guaranteed something new every spring.
When the water seeps into the ground and the ground freezes, the water/ice expands the dirt therefore creating movement. That is why when you build in areas where the earth is moved, you have to go below the frost line. Different depths for different states due to the weather conditions of that particular state. If you built above the frost line it would make your construction unstable when winter came.....it would move the earth below and consequently your structure. If I am incorrect I am sure someone will enilighten me!!! HH