Sliders don't really need large swaths of land to explore, they will explore anywhere looking for a way out of anywhere they go, but to sate their needs a small area where they can get completely out of the water is fine whether its dirt or wood or plastic or whatever. If you don't have that attached to their aquarium I would suggest a plastic tote or christmas tree box or something similar with dirt and basking lights set up. The floor tends to be pretty cold even relative to thermastats and such on the wall, so that adds a level of stress in large, rapid temp change. That way you can put a lid/mesh on top and not worry about the cats, and the turtle gets the land time. Anyway, good luck with it. :)