The late afternoon sun shines into a heavy rain storm, forming rainbows over the crater at Haleakala National Park, Maui, Hawaii. Haleakalā, the eastern of the two volcanoes on Maui, last erupted sometime between 1480 and 1600 AD. (This image was featured on a U.S. Postal Service "Forever" stamp to honor the centennial of the National Park Service.)