Is this a tree root or burrowing animal?
This is interesting! Given the time of year, we can probably rule out any insects that excavate. Yes, tree roots can and will lift pavers as they grow near the soil surface trying to get more oxygen, but the roots would not be pushing up the soil in this manner. We think this may be the work of a tunneling mammal - mole or vole perhaps - that is following the cracks, maybe taking advantage of the root lifing, and removing extra soil from its "runways." If you can, maybe prying up one of the pavers along this route will reveal a channel that the animal has dug. While you can remove the piles and discourage the animal from returning, the tree roots are a more difficult problem to address. Since they need more oxygen, re-leveling the area and/or raising the soil level over them will not only not prevent the problem from recurring, but possibly risk the tree's health as well.
Here is some vole information: https://extension.umd.edu/hgic/topics/voles
and mole information: https://extension.umd.edu/hgic/topics/moles
You can inspect other parts of the yard to see if other tunneling is evident. If not, and no tunnels are present under the stones near these piles, then we may need to probe further for other possibilities.
Thanks much for the detailed and timely response. I too had a feeling it was more of a burrowing animal like a mole. Will try your suggestion and see what's below the paver. I did notice on the other side of my house some holes so perhaps the same creature. Thanks!
You're welcome to send photos of the holes you mentioned, too.
Another possibility is rats, which like to tunnel along edges, especially if there is birdseed or pet food outside to draw them.
So it appears as if the creature found its way out. Noticed these holes in near the pavers. I wonder if that means it got out?
Perhaps, though it would likely be re-using the tunnels for shelter. You could try trapping it if it becomes a nuisance or use a motion-activated camera to capture images of the animal's activities around the burrow entrances.
Okay, will look for a humane trap online and give it a shot. Thanks!