Kaʻū News Briefs, Friday, August 30, 2019

HALEMAʻUMAʻU POND, the first in recorded history, keeps growing. Many days of clear weather since the discovery of the pond on July 25 during a checkup of the now vastly expanded crater have allowed a good amount of study of the phenomenon.
     Assisted by laser rangefinder measurements, U.S. Geological Survey Hawaiian Volcano Observatory scientists state the pond continues to rise at a rate of less than one meter (yard) per week. The pond measures more than 35 meters (yards) wide by more than 80 meters (yards) long. The surface pond is probably no more than a couple of meters (yards) deep. But the visible pond could be just the top of the saturated zone, which could conceivably be several tens of meters (yards) deep.

Telephoto shots of the pond on Aug. 7 and Aug. 23 show the original  three smaller ponds coalesced into one, now more than 250 feet  long by 100 feet wide. USGS photo/ M. Patrick

     Most of the water's surface is opaque greenish-yellow in color, with some semi-translucent blue areas. The temperature of the water is approximately 70 degrees Celsius (158 degrees Fahrenheit). Steam across the water rises slowly and moves with the shifting wind. Shimmering on the pond surface happens intermittently, indicating agitation of the water surface, source unknown.
     Since there has been no major rainfall since the discovery of the pond, scientists surmise the source is groundwater. The local water table is at an elevation of about 590 m (1936 ft; the elevation changes slightly with time), as measured in a deep hole drilled in 1973 about 800 m (about half a mile) south of Halema‘uma‘u. The elevation of the floor of Halema‘uma‘u is about 520 m (1706 ft), 70 m (230 ft) lower than the nearby water table. It is probable that the 2018 eruption drew down the water table during the months of collapses. The water table is likely recovering now, and as it rises, water inundates low areas such as the crater floor.

Halemaʻumaʻu sports a hot pond - the first in recorded history - which is suspected to be filling from groundwater sources.  USGS photo/ M. Patrick

     There is probably a bottom to the standing water, because heat in the plugged magma conduit below the floor of Halema‘uma‘u would boil away water at some depth. But as the conduit cools, the floor of standing water could move downward, deepening the water body from below as well as at the surface. If the body of water is think potential hazards during future eruptions are possible, an explosive scenario HVO scientists are "quite sure" has happened repeatedly in Kīlauea's past. Detailed study of textures of glass fragments in deposits some 400 years old provide evidence of water quenching, when a lava fountain has to push past layers of water.
     If the water body is thin, even rapidly rising magma would not create large explosions because of the small amount of steam generated. If, however, the water is several tens of meters (yards) deep, locally powerful explosions could ensue, probably not large enough to diminish public safety but perhaps big enough to create a nuisance ash fall during unfavorable wind direction.

     At present, state HVO scientists, monitoring data show no signs of impending eruption, and it could be years down the road before the next summit eruption happens.

     Learn more at volcanoes.usgs.gov/volcanoes/kilauea/multimedia_chronology.html.

To read comments, add your own, and like this story, see Facebook. Follow us on Instagram and Twitter. See our online calendars and our latest print edition at kaucalendar.com.


To read comments, add your own, and like this story, see Facebook. Follow us on Instagram and Twitter. See our online calendars and our latest print edition at kaucalendar.com.