A cavers’ map is dotted with question marks, indicating where other cavers have spotted a crack or crevasse that offers a possible unexplored passage. Some become impassably small. Some dead-end in alcoves. Others open into ballrooms of crystalline features, mineral fingers that trace lines drawn by dripping water.
“Imagine a tunnel, and nobody has ever been there. You walk into this passage, and what’s around the next corner, nobody knows,” says Max Wisshak, a geoscientist, caver, and co-editor of . “Maybe you find something new that not only
