We live in an era when Earth has been considered long-conquered. The highest mountains, darkest rain forests, the Arctic and Antarctic wastelands have all been explored and mapped. The ocean’s deepest points have been plumbed and detailed isobenthic maps exist. These former frontiers are now relegated to places for ever more detailed scientific investigations (especially the oceans for their bio-diversity), extreme sports, and for commercial exploitation. But as places for true exploration they are a part of history.
While truly known only to a handful of teams worldwide, the last -- and arguably the most technologically and psychologically challenging -- terrestrial frontier is being systematically explored in our time: that of extraordinarily deep cave systems. And, like the original exploration of the Poles, and the race to climb Everest, there is a quiet, yet spirited competition now to explore the once-and-for-all-time deepest natural abyss on Earth.