Cave popcorn (noun, “kayv POP-korn”)
Cave popcorn is a kind of cave formation. These knobby clusters of minerals decorate cave walls and ceilings. They can also cover other cave formations, such as stalactites and stalagmites. Sometimes, cave popcorn is made up of many tiny bumps bunched close together. This can create a cauliflower-like texture. Other times, cave popcorn features larger, cherry-like blobs. Cave popcorn is part of a larger group of bulbous cave formations known as coralloids.
Cave popcorn typically forms when mineral-rich water splashes or seeps onto cave surfaces over hundreds or thousands of years. As the water evaporates, it leaves minerals behind. Over time, these minerals build up and clump together.
Most cave popcorn forms through evaporation. But some forms entirely underwater. This can occur when water is “supersaturated” with minerals. That is, it contains more dissolved minerals than it can hold. The dissolved minerals can “fall out” of the solution. And sometimes, that forms popcorn-like deposits.
Like other cave formations, popcorn is thought to grow about 1 centimeter (about half an inch) every 100 years. Most cave popcorn consists of calcium minerals, such as calcite and gypsum. These minerals usually give the popcorn a whiteish color. However, some caves contain formations made of other minerals, such as salt.
Often, cave popcorn looks especially bright when growing. But as water flow changes, and the formation growth slows, it may darken. Some elements imbue cave popcorn with colorful hues. Iron may give it an earthy reddish color.
In a sentence
In Poland’s Wieliczka Salt Mine, cave popcorn, straws and other formations — all made of salt crystals — adorn the surfaces.
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