Because the shorter wavelength components, such as blue and green, scatter more strongly, these colors are preferentially removed from the beam.

The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange.

[9] Ash from volcanic eruptions, trapped within the troposphere, tends to mute sunset and sunrise colors, while volcanic ejecta that is instead lofted into the stratosphere (as thin clouds of tiny sulfuric acid droplets), can yield beautiful post-sunset colors called afterglows and pre-sunrise glows.

A number of eruptions, including those of Mount Pinatubo in 1991 and Krakatoa in 1883, have produced sufficiently high stratus clouds containing sulfuric acid to yield remarkable sunset afterglows (and pre-sunrise glows) around the world.

The high-altitude clouds serve to reflect strongly reddened sunlight still striking the stratosphere after sunset, down to the surface.