My experiments with volcanoes

by Thomas Augustus Jaggar

I hoped and prayed that the commercial packet, the Mauna Kea, might take me to Hilo. But no, the navy tug Navaho came from Lahaina, and Captain Green put up his megaphone and announced that the Admiral’s instructions were that he was to take Dr. Jaggar to Hawaii. My heart sank because I knew what a seaway would be running against that little tub. The second rescue ship proved to be the Pelican equipped with a crane to swing the plane on board and take it back to Pearl Harbor.

On board the Navaho I was assigned a canvas camp cot in the lower, circular wheelhouse at the bow; and all night long waves broke over the bow and a foot of water sloshed back and forth under my cot. The pitching was so heavy and our speed so reduced that it took us all night to get across the Hawaii Channel, and we didn’t make Hilo until 2 P.M. the second day. After that wet and seasick night, I found wry humor in our reception at Hilo Wharf, where we were met by Frank Cody with his motion picture camera and a bunch of hula girls and leis. Instead of five hours, the journey took thirty and quite failed to make me air-minded. Furthermore, I arrived at Kilauea Volcano in time for only the final stages of the explosive eruption.

Finch had organized volunteers, including Oliver Emerson as photographer, and even our collie dog, Teddy, who could hear and feel an explosion coming before we had any other warning. All observers wrote notes and fondled the seismographs during the three weeks of steam blast and cavings in of the pit, which had enlarged itself by collapse 700 feet outward radially in all directions. When I got there it was 3,500 by 3,000 feet in diameters and 1,300 feet deep, the bottom a funnel of converging taluses, made of avalanches from the pit walls. The taluses were wet and steaming vigorously in vertical lines, and at night showed red hot avalanches from the north and west walls, where two intrusive bodies of hard rock were red hot inside. The talus below stayed hot, and slides occurred for only a few seconds. The incandescent matter was not flowing in any sense, but was, rather, the peeling of a rocky boss of reddish color at the west and a canoe-shaped ledge at the north about 600 feet below the rim.

This showed the cross section of old screes, revealed above it, and horizontal basalt flows overlapping above that. It was a beautiful section of an ancient pit, of the same quality as Halemaumau itself, and the incandescent canoe sill at the bottom appeared to be an intrusion of fine-grained gabbro, which had pushed its way in under an older talus funnel, similar to the present talus cup of Halemaumau, the bottom of which was 700 feet lower.

On the opposite wall of the pit the Kau Desert rift was displayed as a vertical cavern or arcade, merging into a group of dikes higher up and tapering to zero thinness at the top. These same dikes, less conspicuous, cut the canoe sill on the northeast wall, to indicate that the ring of the pit was fractured vertically from below. This fracture is the main deep rift of the mountain which crosses under Kilauea, bending in the direction of Kilauea Iki, and this it was which had opened as a curved chasm to let the lava down. Lava had gone down in a succession of flank outflows, with intervening rises, from the Kau Desert in 1920 to the final drainage under the sea at the east. This drainage had let in the groundwater, made a steam boiler, and so caused the explosive eruption and engulfment of Halemaumau walls as the mountain yawned open.

A. L. Day made one of his return excursions to Kilauea at this time and thus saw the extraordinary phenomenon of the hard basaltic intrusive bodies half way down the walls, caving to a red hot talus. The explosions, which started with two-hour intervals, gradually decreased, coming at four hours and eight hours; and on May 18 came the culminating cauliflower clouds with torrents downward of broken rock, some of it showing low red heat. At all times the motive power was steam jets 10 to 15 thousand feet high, which plastered the pahoehoe of the pit edge with broken wall rock fragments of every size.

There was no sign of pasty lava or glassy bombs in the ejecta, and the red incandescence seen at night in some of the explosions was the avalanche material of the western boss and the canoe sill.

It took the pit less than two months, to mid-July, to recover its liquid lava, which poured through the talus and made aa puddles, to form a new pattern of cone source and short-lived flows. Then everything came to rest, and lava activity was not resumed there until the summer of 1927. However, in 1926 Mauna Loa went into action on its southwestern rift, and sent an aa flow into the sea at South Kona, destroying the village of Hoopuloa.

Here was history in the island lava column of majestic decline and recovery from 1914 onward. Outflow in Mauna Loa crater at 13,000 feet in 1914 extended to outflow from the southwest rift in 1916 and 1919 at 8,000 feet. Next, in 1920, came outflow in the Kau Desert from Kilauea, at 3,000 feet. There were alternating spurts upward within Halemaumau pit, acting as a crater similar to Mauna Loa’s at the lower Kilauea level of 3,700 feet.

Then this whole progress downward moved over to the Chain of Craters at 2,500 feet, and finally to the ruptured earthquake rift of Kapoho on the east point of Hawaii and at beach level. Some miles farther east, on the same rift beneath the sea, the gigantic submarine mountain of Hawaii drained the last lava from Halemaumau pit and let in groundwater which caused steam explosions.