In 1948 Observatory work was returned to the administration of the Geological Survey, and a volcanologic branch in Denver took over Dr. Powers to make airplane studies of the Aleutian Islands. This was under Mr. Walter Frederick Hunt, in charge of geology, U.S. Geological Survey.
When Hawaii National Park was reorganized, Frank Oberhansley, superintendent, the Natural History building was adopted as Park Headquarters, and the Uwekahuna buildings, with their magnificent view in all directions, were reconstructed as the Hawaiian Volcano Observatory. A new seismograph cellar was dug, away from disturbances of Uwekahuna cliff, and modern instruments were installed. Mr. John Forbes became assistant machinist; and on Mr. Finch’s retirement in 1951, Dr. Gordon Macdonald became volcanologist in charge. C. K. Wentworth moved from Honolulu to the National Park region and took charge of magnetic measurement, which had been established at numerous stations by physicists of the Geological Survey. During past decades physicists and chemists had visited the Observatory, among them Dr. Stanley Ballard, who equipped the laboratories with a Gaertner spectrograph; Dr. Harvey White of Berkeley, who found no radioactivity in Hawaiian lavas; and Dr. J. J. Naughton, who found a critical isotope of carbon in the emanations of Sulphur Bank. Modern chemistry was beginning to be applied to volcanology in the field, and this was what Hovey, Perret, and I hoped for fifty years ago. So much for dry facts of organization.
In 1949 the summit crater of Mauna Loa erupted, with fracture and outflow of its south end toward Kona. This was followed in 1950 by lengthy rupture of the southwest rift with the most voluminous and rapid outflows of history, three of them going into the ocean and wreaking destruction in South Kona.
The sequence of these outflows was from high sources first, with others opening farther south, and the most conspicuous flows following the steep Kona slope into the ocean, beginning at Hookena. Macdonald and National Park naturalists photographed and recorded everything. The old Hookena post office on the upper road at the home of the veteran Mr. Lincoln was carried away, and this occasioned much drama, for the old man didn’t wish to leave his home. The next house destroyed, an old landmark, was the Magoon Ranch. The third was the attractive and modern Ohia Lodge, a resort built of native logs in the wilderness.
A separate large flow forked away from the rift, to the eastern side of the mountain, reaching the lowest landward elevation in the forest of Kahuku, and short flows spilled over the southwest rift on the east side.
Several persons approached the flows in South Kona from the ocean. The early photographs of the first flows, where the hard sprouts and boulders of stiff aa partially cooled entered the ocean, showed big columns of vapor from contact with sea water. Not so with the third flow farthest south, explored from a canoe by Jack Matsumoto and a companion, equipped with motion picture cameras. The pictures were good color photographs, and the torrent of lava flowed down a steep bank of its own substance, hemmed in by hardened ridges at the sides, the stream intensely liquid and flowing directly into the ocean.
The result was most remarkable. The yellow liquid lava went into the salt water without making any column of steam at all; the sea bottom simply received it with its rush downward, the water boiling superhot, and the lava taking the water vapor into itself. The phenomenon was not due to the rising of dry steam, for there was no condensation cloud above. Scientists explained it by assuming a shell of lava making a tunnel under the ocean, with the crust ending just at sea level.
Such a submarine arch was definitely not present, for the waves surged back and forth and, Matsumoto states, there was no sign of a submerged reef. The motion picture bears this out. What was probably going on is what happens to slag in a patented process of the steel mills, where the glow liquid is flowed over a perforated surface emitting hundreds of water jets, and the melt at 1300° Centigrade absorbs the water without making visible steam. The slag turns into a myriad of microscopic glassy spheres, becoming a kind of pumice. A peculiarity of this substance is that if it is cooled at 700° Centigrade it will pass a critical point and give up the absorbed water with explosive effects. It seems likely that Matsumoto’s golden torrent sweeping into the ocean was so excessively hot that it took up the water and continued to flow down the sea bottom as a water-charged product. The snapping and crackling effects, and the submarine earthquakes, making localized tidal waves such as those noted in 1919 when such a torrent entered the sea, may be due to the explosive cooling when the slag gives up its water.
The use of color motion pictures is one of the many improvements owed to modern science, and the mapping of lava flows by airplane photography. This gave Macdonald a new weapon for surveying the volume accumulation at the time of the 1950 outflows, for from air photographs he got exact outlines of the flows. These, checked against calculated thicknesses, gave him volumes which could be compared with volumes of older flows proportionate to areas. These calculations showed that nothing since 1868 has yielded such large volumes of lava, per days of outflow.
Mrs. Jaggar and I were returning to Hawaii from a trip to Nova Scotia, and the Matson steamer Lurline took us to the Kona coast toward the end of the 1950 eruption, for inspection of the glowing flows late at night. They looked like hot coals extending far up the mountainside under the clouds, with occasional bright flares where trees burst into flame. Visible motion there was none, as we were too late for the rapid flowing and too far away to see detailed motion. This eruption resembled the voluminous flow of Mauna Loa in 1868, from a low vent at the south end of the mountain, and lasted only a short time after preliminary summit outbursts. The similarity was a big earthquake series, and this was to happen again in Kona in 1951. The cataclysmal opening of the southwest rift in the nineteenth century eruption followed a quarter century of northern outflows, those from 1843 to 1859. Next came those from 1929 to 1952 in the twentieth century. The 1929 earthquakes subterraneously began the northern series.