These first ten years of the Observatory answered many questions and pointed the way for future experiment and study. It now appears that liquid lava is a gas froth, that Kilauea and Mauna Loa are all one system, that hydrogen is the most elemental gas in eruption, that a gas-free paste is the residue of flowing foam both in pits and lava flows, that earthquakes and vibrations are a function of this paste wedging up cracks and sinking back underground, and that the rise and fall is in tides and cycles, short and long. These things are not guesses, but measurements.
The earthquake problem at volcanoes is misunderstood in geology. The superstition that volcanic quakes are small is wrong. “Volcanic” in volcanology is not limited to volcanoes. Los Angeles, Charleston, Lisbon, and the deep ocean bottom are all volcanic, are all tremulous; and all have “lava” underneath. Kilauea and Midway Island are one, Rome and Etna are one, Iceland and St. Helena are one, Redlands and Mount Rainier are one, and the paste is underneath. These facts concern the globe, not a little bundle of wrinkles like the Alps.
We do not know what an earthquake is or what lava is. However, “lava” falling suddenly and rising slowly with big and few earthquakes accompanying fall, and little and many earthquakes appearing with rise, are facts observed at Kilauea. At Tokyo in 1923 the greatest quake in history centered at lowered lava and lowered sea-bottom next to Oshima Volcano island. The Messina quake in 1908 made a hissing noise, and nearby Etna lava was low. There are long cracks in the earth shell somewhere deep down, and we know little about them except that volcanoes and faults are in lines. So long as the three-quarters of the globe under oceans are unexplored by man, with no rock specimens or even decent maps, and so long as there are no instruments planted on sea bottoms, we cannot use the term volcanic intelligently. Most volcanoes of the earth are undiscovered. Kilauea measurements whet the appetite for a new scientific frontier, the prospecting for ores, volcanoes, and mountains under the sea. The absence of core drilling and rock sampling over three-quarters of the earth is a disgrace to the oil-drilling and quarrying sciences of mankind.
The founding decade of the Hawaiian Observatory produced two effective expeditions, one to Japan and one to New Zealand.
The Research Association voted to send me to Kagoshima in Kyushu, the south island of Japan, where the volcano Sakurajima made earthquakes, explosions, and lava flows in January of 1914. About the same time Perret was sent to Sakurajima by Friedlaender of Naples, so we met in Japan.
Sakurajima, or Cherry Island, is a 4,000-foot cone in Kagoshima Sound, a deep inlet at the southernmost end of Kyushu. The volcano threatened 22,000 persons in villages on Sakurajima Island itself, and 70,000 in Kagoshima. It is a land of orange groves, fisherfolk, Satsuma porcelain, and maritime commerce, situated at the north end of the Okinawa-Ryukyu islands, a volcano chain extending north to Nagasaki.
Authorities in Kagoshima knew all about Pelée; and the army, navy, and governor wasted no time. Professor Omori, who had a seismograph at the weather station of Kagoshima, went at once to the volcano, and profiting from the lesson of Pelée, guided the lives of 90,000 persons.
The Sakurajima eruption began on a Saturday and Sunday with hundreds of earthquakes locally identified as coming from the volcano. Public and private vessels were called into service to move all the people of the island over to Kagoshima and beyond. With a general of the army in command, this was accomplished in two days. On Monday at ten o’clock the great, picturesque peak, quite like Pelée or Vesuvius, suddenly ejected vertically and quietly, from a crack in its flank, a column of “smoke” 30,000 feet high. This was answered by another, similar column on the opposite side of the mountain; and the two columns joined above into a colossal arch of cauliflower clouds consisting of sand, dust, and boulders. The crack in the mountain which gave vent to all this opened with slight rumble and behaved like two radial ruptures meeting toward the peak, extending southwest and southeast. The sector of the mountain between them appeared to have been lifted like a piece of pie shoved up in the center. But the summit craters played no appreciable part in the eruption, unless it was a gush of steam on Sunday evening. The line of craterlets along the cracks and only half way up the mountain quickly developed lava flows, and these poured down, the one toward Kagoshima Strait, the other toward the narrow Osumi Strait, which separated the volcano from the wilder eastern mainland. This strait was filled up with heavy block lava, or aa, converting the island into a peninsula. A similar aa lava flow, fifty feet high in front, swept down to the beach on the Kagoshima side, with boulders as big as a house tumbling over its andesite front.
Tidal waves made by these two lava flows entering the sea were small but perceptible. The principal effect was thousands of white steam jets where the red hot blocks entered the ocean. Culmination of glowing heat came the second night, Tuesday. The flows continued for months, but the maximum of seismic effect had happened at six o’clock in the evening of the first day, Monday.
This was a really big earthquake damaging masonry and causing landslips from the cliff next to Kagoshima city and killing a number of people. The flux of refugees from the volcano villages on Monday was a dramatic event. When the lava outbreak occurred in the forenoon, the schools sent the children home. On their way, the children gazed entranced toward the terrific arch of cloud over the mountain, vomiting trajectories of stones. Shops closed, and the city was quiet while everybody sized up the crisis. As a schoolboy in English class wrote, “Monster rocks went horizontally from the down to the up, with smokes on their behind.”