Nearly 40 years ago, boiling water, towering chimneys, and a menagerie of weird creatures stunned researchers who were trying to study the seafloor 250 miles (400 kilometers) northeast of the Galápagos Islands. They had stumbled upon hydrothermal vents, which made for a hellish world completely cut off from sunlight.

The discovery upended our view of life on Earth, which until then had been based on the assumption that life couldn't survive without the sun's rays.

Ocean explorer Robert Ballard was part of the original expedition, and he recently revisited the area known as the Galápagos Rift to study how it had changed.

Hydrothermal vents are ephemeral habitats dependent on heat from the mantle below to power them. New eruptions can obliterate vents, and tectonic plate movement can carry them away from their heat source.

When Ballard, a National Geographic Explorer-in-Residence, and his team arrived at the Rift this past June, they found chimneys that were active in the 1970's had been destroyed by new lava flows. New vents had popped up nearby, and species previously seen only in other parts of the world were sprinkled throughout their survey areas.

To see what they found, click through the following ten pictures.