Twilight: Twilight | Silhouette | Calm
While this prompt is about Twilight and Silhouette it is also about taking the photo using an iPhone. I must admit I didn't use the iPhone as a camera very much at all. Not while I've got a nice DSLR to use. So I'm veering off topic.
In the thermal spring areas the flow from the springs tends to kill off the surrounding flora due to the high levels of chemicals in the springs. There was such a desolate and barren feel to many of the thermal areas with the dead trunks remaining. This is taken at Yellowstone National Park.