Whether it "comes on little cat feet," as poet Carl Sandburg whimsically suggested, or rolls in like an ominous tsunami cloud, fog is one of Mother Nature's most magnificent displays. It can veil the dawn in delicate beauty or shroud an entire city in gloom. It has even been known to kill.
This atmospheric marvel is actually a cloud that touches the ground, formed when water vapor in the air condenses around microscopic dust, salt or other particles and morphs into suspended water droplets or ice crystals. And like overhead clouds, fog isn't a single entity that varies by degree of murkiness. It comes in several distinct varieties that are influenced by nearby bodies of water, landscape features and other local factors. Here are some of the most impressive forms of fog on the planet.