Telescope Peak
Death Valley was once a very shallow ocean like the Bahamas. Telescope peak was created millions of years ago by titanic plates hit each other forcing volcanoes up to the surface. Forcing the ocean back. It used to be all mountains but then scene the continents were still moving some of the mountains sunk and that's what created Badwater basin.
Sand dunes
Sand dunes were created by wind picking up the sand and putting it some were else. In this case the sand is coming from eroded canyons. washes provide plenty of sand, the wind seems to always blow (especially in the springtime), but there are only a few areas in the valley that you can find sand dunes.