I have a tree in my backyard and can't identify it. I've enclosed two photos of the leaves. Most are approximately 5-6 inches and single lobed, with saw tooth along the edges. The ones that get the most sun though are about 8 inches and three lobed (and huge). There are no visible flowers or the like anywhere on the tree. The bark is gray and deeply furrowed. This is in Susanville, California, USA. Any help would be appreciated!