Caves tell stories about what the climate used to be. One of the ways that caves guard climate secrets is in speleothems. These are mineral deposits that accumulate inside caves upon years of sedimentation and water seepage. You may recognize stalactites and stalagmites as typical cave formations– both of these are forms of speleothems.
Speleothems are formed as a by-product of a reaction between water (usually rainwater), carbon-dioxide from the atmosphere, and rocks that contain calcium carbonate. The chemical reaction between these three forms calcite deposits, which is the same material that chalk is made from. Speleothem formation is a very slow chemical process that takes tens of thousands of years. They grow almost 1000 times slower than human hair!
One scientist who is trying to understand what these rocks can tell us is a paleoclimatologist named Kathleen Johnson. Read the post on Dr. Johnson's amazing research, and then follow along with this activity to grow your own speleothems at home! Real speleothems in caves may take thousands of years to form, but you can grow your own tiny versions of the rocks at home much quicker!
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