8. A cumulonimbus cloud near Waterville, KS, exhibits a form called mamma,
which are the bulbous protuberances hanging from the lower side of the cloud.
They can produce spectacular displays, especially when the sun is low in the sky.
Despite their common occurrence, beauty, and wide variety of speculations regarding their origin,
mamma remain somewhat mysterious. Mamma can often be seen on the lower sides of cirrus,
altocumulus, altostratus, and stratocumulus clouds, as well as cumulonimbus.
They have also been observed on the base of volcanic ash clouds
(see the cover of National Geographic, January 1981).
(Photo courtesy of David K. Hoadley, copyright 1977.)