PLANET EARTH Caves

They named the cave** 'Lechuguilla' **（墨西哥龙舌兰）and since this discovery more than 120 miles of passageways have been mapped. When the first explorers descended, no-one guessed at the sheer size of this cave. But even that was not going to be the biggest surprise. Little did they realize that Lechuguilla would soon be regarded by cavers the world over as the most beautiful of all caves. They were about to discover some of the most exquisite（精致的） formations ever seen underground.



The walls were covered with the most delicate and fragile crystals. Many of these crystals were made of gypsum（石膏）, a mineral that comes from limestone. And there was mile after mile of them. Water is the creator of most caves, but, unlike all other limestone caves, Lechuguilla's rock had not been eaten away by running rainwater. Something else was responsible.



The only water Lechuguilla has are these wonderfully still clear pools. As the explorers went deeper into the cave, they came across whole galleries filled with the most unusual formations, like these 5-metre cones, frosted with the most delicate crystals. It was Lechuguilla's gypsum crystals that made scientists question how these caverns were formed.



They discovered that Lechuguilla's limestone had actually been eaten away by sulphuric acid, cutting through literally miles of limestone. And when sulphuric acid dissolves limestone it leaves behind gypsum, the basis of Lechuguilla's remarkable formations. And there was one set, more than a mile from the surface, that almost defied belief.



The Chandelier Ballroom was the ultimate discovery. With its six-meter long crystals it's surely the most bizarre cave chamber in the world. And the walls had one further surprise. Extremofile bacteria were found to be feeding on the rock itself. The discovery of life that exists without drawing any of its energy from the sun shows us once again how complex and surprising the underground world can be.



Each year explorers chart over a hundred miles of new cave passages. But with half the world's limestone still to be explored, who knows how many Lechuguillas are still waiting to be discovered?