U


li Kunz stared down into the


sinkhole. T is dark hole is the opening to a deep cave. T e cave is full of water. T ere is no light and no air there. T ere would be no hope if he got lost. Yet Kunz was excited. He was


going to explore the cave and take photos. He and his team had trained hard for this adventure. He hiked through jungles with his eyes closed. He used only a guide rope find his way. He practiced swimming through tight spots. He swam with his bulky camera gear. He felt ready, but he worried that


something could go wrong. His lights could fail. He could run out of air. He could get lost. He checked his gear one last time. T en he jumped into the water.


UNITED STATES


Carving Caves Kunz is in Mexico. A rain forest covers the land. Hundreds of caves that are fi lled with water lie under it. T e caves tell a story of weathering. Long ago, this land was solid


limestone rock. Year aſt er year, rain soaked through the dirt on top. As the water moved through the dirt, it became an acid. T e acid dissolved pieces of the rock. T is made the limestone turned soſt . Time passed. Aſt er millions of


years, gaps formed in the rocks. More rainwater dripped into the gaps. Ocean waves rushed in and out. All of this water eroded the rock. T is erosion carried away pieces of rock. T e gaps in the rocks got bigger. Many became caves.


Yucatan Peninsula


PACIFIC OCEAN


Flooded! New rocks formed inside the caves. Some hung like fangs from cave ceilings. Others rose from cave floors like towers. Some even looked like bells. T en Earth started


to warm up. Ice melted. Oceans rose. T e rising water flooded the caves.


12 NATIONAL GEOGRAPHIC EXPLORER


MEXICO


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