We went caving again this past weekend, exploring somewhere truly special. We had secured special permission to enter a restricted, incredibly fragile cave that very few people ever get to witness. The highlight was a ceiling blanketed in thousands of delicate straws.
These straws are formed by the slow, steady drip of mineral-rich water over thousands of years. As rainwater seeps through the earth, it dissolves calcium carbonate from the limestone above. When a single drop hangs from the cave ceiling, carbon dioxide escapes into the cavern air, causing a microscopic ring of calcite to crystallise around the edge of the water droplet. When the drop finally falls, the next one takes its place, adding another tiny ring.
Layer by layer, year after year, these rings build downward to create a hollow, glass-thin tube. The water actually flows down the inside of the straw. They grow agonizingly slowly…often just a fraction of a millimeter per year, meaning the delicate formations suspended above us had been quietly building in the dark for millennia.
