My visit to the park took me to the eastern end of the National Lakeshore, where you can find one of the park's taller dunes, Mount Baldy, which stands an impressive 126 feet tall. You see the dune right away, as the parking lot is right up against it.
Science Lesson: How does a sand dune move? Well, the prevailing winds come in from the direction of Lake Michigan, and as these strong winds blow, they pick up and carry grains of sand and dust up the windward side of the dune (the side facing the lake), and blow it over the top where it then rolls down and settles on the leeward side (the side opposite from the lake). The leeward side faces the parking lot, so that's the side we're looking at here. So from our perspective, the dune is moving toward us.
All those trees you see seemingly growing out of the side of the dune? Well, when they first sprouted, they were on flat ground and the dune was standing behind them, much closer to the lake. In the time it's taken those trees to grow, the dune has moved inland enough to subsume over half of their height! Eventually, the dune will move far enough forward to completely cover them in sand. It will take years, but it will happen.