On the way over to Great Basin National Park last week, I grabbed this quick photo of the alpenglow hitting the west side of Wheeler Peak (13,063 feet ASL), partly because the lower line of the pinkish band was hitting the mountain at just about tree line. The pinkish band is sometimes known as the Belt of Venus or antitwilight arch, at least when it is seen in the sky, and the dark purplish blue area below the alpenglow is the Earth's shadow on the mountain. It is sometimes called the dark segment, at least when seen in sky.
If you happen to be standing on a mountain when this pinkish phenomenon is visible to those to the west of you, you will be standing in the pinkish, dying light of the sun, just before it goes below your western horizon (presuming you aren't in Alaska or somewhere very far north or very far south, where the sun doesn't always set in the west, but can set in the north or south, or not set at all). As the pinkish, last light of the sun leaves you on your mountain perch, the terminator will come upon you, you'll be in the twilight zone, and then you will pass into the night (all while standing still).
In this grainier enlargement of the same photo, you can see that the pinkish alpenglow isn't exactly congruent with tree line in all places.
We drove on, to find and set up camp in the dark, at about 9800 feet on the other side of that same mountain.
Recent Great Basin N.P. Blogospherics:
A Park without it's Namesake at Geotripper
We Head Underground in the Great Basin at Geotripper
Great Basin National Park at Nature's Blog
My Backyard - Great Basin NP at WATCH FOR ROCKS