A pond of dazzling water is growing at the bottom of Halema’uma’u Crater, a large pit crater located in Kilauea caldera on Hawai’i Island, baffling scientists who say they aren’t sure of the water’s source.
The mysterious pool was spotted on July 31 when geological LIDAR surveys observed a “ small, green patch within the deepest visible area of the new summit caldera,” reported the US Geological Survey (USGS) at the time. Two small pools continued to grow, eventually merging together. Routine laser rangefinder measurements indicate that the pond continues to rise at a rate of just under 1 meter per week. Photos captured by the USGS show how the ponds increased in size over the course of just two weeks.
"What a difference a fortnight can make! These photos show the growth of the water pond in Halema‘uma‘u over a period of two weeks," said the USGS. "On August 7, the main pond was about 15 meters wide and separated from two smaller ponds; by the next day, the water level has risen enough that all three ponds were joined. On August 23, the single elongate pond was about 35 meters wide and about 80 meters long—and still growing."
The video below, captured by the USGS on August 31, shows a close-up of the fumaroles on the north side of Halema‘uma‘u and a broader view of the crater with the water pond at its base, steaming and rippling along the surface of the chalky green water. Estimates suggest the water surface temperature is around 70°C (158°F).
Scientists are working to confirm its origin as they are not sure where the boiling water is coming from, but believe it could be related to last year’s eruption. Kilauea erupted for several months last summer and put on quite the performance, from boiling down a freshwater lake and producing its own thunderstorm clouds and tornado, to making blue fire and new land along the coast. After a series of collapses, the bottom of the crater is now lower than the top of the water table.
“I would guess that barring any kind of disturbance, it will continue to percolate in and eventually equilibrate so that the water table and the water level in the crater are more or less the same,” said geologist Scott Rowland in a statement. Water has not been observed in the crater for at least 200 years, but Rowlands adds that Hawaiian legends mention water found at its depths.
The Hawaiian Volcano Observatory, one of five observatories in the US Geological Survey, will continue to monitor the pools.