Thuja occidentalis

Roots of the Northern White cedar.
Heart Lake, North Elba, NY. 

The roots are pretty shallow and this tree was exposed on the edge of the lake, so I imagine the tree was downed easily. In any case the wood of the cedar, even of the roots, is very resilient, that is resistant to decay by moisture and other elements. The "aged" roots are quite beautiful, so you'll see them as decorative pieces in homes throughout the U.S.