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Exploring CavesSkip Navigation | Main Page | Teacher's Guide: Download | Multimedia ResourcesExplore Caves: Cave Types | Cave Animals | Cave Care | America's Caves Story: Ch 1 > Lessons | Ch 2 > Lessons | Ch 3 > Lessons | Ch 4 > Lessons | Ch 5 > Lessons Most American caves are big holes that form in limestone rock. The holes begin as cracks in limestone. The cracks get bigger and bigger. They grow into underground streams, rivers, and even lakes. When water drains away, the waterways turn into open cave tunnels, passages, and caverns. It takes 10,000 to 100,000 years to form a cave big enough for people to move around inside. Water drips constantly in caves. The drips dissolve limestone minerals in one part of the cave. As water dries out, the minerals build up in other places. In this way, beautiful cave rock formations and crystlas grow over thousands of years. These rock formations change dark limestone caves into hidden fantasy lands. Poster is now a sale item. |
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