The black-water river didn’t plunge into a stale sump. It widened into an underground sea.
At six thousand five hundred meters beneath the surface of the fractured continent, the narrow dark rock canyon that had funneled the Iron Ark through four days of grueling descent suddenly fell away. The air, which had grown steadily hotter and more stale as they navigated the upper chimney pipes of Outpost 09, cleared with the crisp, shocking coolness of an ice-slow valley. Arthur Vance stood on the forward watching deck of the lead command hauler, his heavy canvas duster whipping in a nonstop, moisture-laden gale that blew upward from the deep pit.
Before them stretched the Sunken Bioluminescent Aquifer of Trench 05.
It was an underground expanse so vast that the distant limestone bluffs were lost in a pale turquoise haze. Four hundred meters overhead, the arched ceiling of the world-size mantle was carpeted with huge colonies of deep-sea bryozoans, glowing cave-sponges, and weeping tendrils of eerie-glowing moss. They shed a gentle, twilight-blue radiance that reflected across the mirror-flat surface of a huge underground lake. The water was so pure, so fully empty of heavy-duty silt, that even in the dim bioluminescence, Arthur could see down through forty feet of crystal-clear depths to the white quartz sand below.
