THE REGION OF THE DISCHARGE OF 1840 AS DESCRIBED BY.
Captain Wilkes went over the ground traversed by this erup tion January 18th to 23d, 1841, and published a map of the region. He used the name of Lua Pele for Kilauea iki. A short distance from this he observed a deep crevice about four feet wide, extending in a southerly direction. At two miles he passed the pit-crater Kalanokano. This new term he explains as a crater "of which there is no appearance whatever until one is close upon it, and which never throws out lava." It might have been formed by the undermining of the part beneath them, as by a stream of lava, which running away had left large cavities with out any adequate support, and the superincumbent rock would fall down. Some of these pit-craters are from eight hundred to i,000 feet deep. The other craters he describes as hills of scoria and ashes formed by the ejection of lava, and gives them the name of cone-crater.
The first cone-crater met with is about a mile beyond Kalano kano, called Puukehula, about eight hundred feet high above the plain. From its summit eight pit craters were visible ; four on the Kilauea side, one at the foot of Puukehulu, and three others to the east-southeast with two cone craters Moka-opuhi and Kane muokama. The pit crater Alealea-iki, at the foot of Puukehulu is about five hundred feet deep, and shows that a stream of lava has flowed into it. Kanemuokama is the largest of all the pit craters except Kilauea, and an old crater adjacent the most regular of any that the exploring party had seen upon the island. The new eruptions on both sides of Moka-opuhi appeared simultaneously upon May 31st.
For several miles the country consists of rough lava clinkers overgrown with grass and stunted shrubbery, where walking proved to be irksome and dangerous. About thirteen miles south east from the new opening is the cone-crater of Kalalua of the altitude of I,Too feet above the plain. It has sent forth streams of pahoehoe. At the altitude of 1,244 feet, twenty-seven miles from Kilauea, twenty-one from the first outbreak and twelve from the seashore at Nanawale, is situated the commencement of the final outbreak. It began in a point, gradually enlarging, and in two miles became a torrent of fluid rock from ten to fifteen feet thick, sweeping everything before it. The fallen timber still re mained, only holes were left to show where it once stood, the stumps having been entirely consumed, sometimes reaching a depth of twelve to fifteen feet. In some places lava was found adhering to the leaves and branches of trees. A copse of bam boo remained in the midst of the flow, and many of the trees were still living. Some large trees not more than twenty feet from the stream were scarcely affected, while it was still possible to light walking sticks two feet below the surface and only thirty yards from these living trees. This was eight months after the eruption. Nearer the sea all the foliage to the distance of three
hundred and fifty yards from the lava stream was killed. The slope of this stream was about one hundred feet to the mile, and its velocity was estimated to he about four hundred feet an hour.
Wilkes observed many fissures along the whole line and thinks that lava must have flowed from them, as lava seems to have is sued from them in some cases. Where the ground was steep, underground tunnels were apparent. The upper part of the stream consisted of pahoehoe, and much of the lower part, while some what suggestive of clinkers (aa), was to be compared with the slabs of ice in rivers when broken up by the force of the current. About six miles from the sea there seems to have been a simultane ous outbreak over a large area. Occasionally a "blowing cone" was seen with quantities of salts, sulphur and hot gases still issu ing from it.
At the sea the lava fell over a cliff into the water for a width of three-quarters of a mile. There were three sand hills, evi dently accumulated from a shower of shivered particles of lava that prevailed while the fiery cataract existed. They were one hundred and fifty and two hundred and fifty feet high when Wilkes saw them. Brigham says they were not a third as high in 1864. And in 1883 and 1899 when seen by myself, they were still smaller, because of the action of the sea. The sand originally extended about one hundred feet into the ocean. There is more olivine in this sand than is common in the lava ; due probably to its higher specific gravity.
Wilkes' figure of these sand hills represents a fissure between them, but his mention of the sand storm would seem to imply an eolian origin. Dana's figure made in November, 1840, does not indicate any fissure, but in his text he calls them examples of ele vations thrown up suddenly over fissures of eruption. "They consist of a rusty yellow tufa, distinctly and finely laminated." Had he not adhered to this theoretical statement down to his latest publication, it would seem as if he had himself shown the way to a better view, for he says: "The sands are said to have been thrown out from the center of each hill while in progress; yet there was no cavity at top. As the molten lava met the sea there was a violent explosion and an ejection of fragments which fell around the center of eruption ; and owing to the water which as cended and descended with them, the structure became laminated." The stratification is concentric : hence the layers were entirely of eolian origin. It is easy to contrast the structures of these sand hills with tuff cones formed near the seashore in the normal eruptive way. These always show a hollow interior. I have found these peculiar sand hills on the edge of the sea in other parts of Hawaii and Maui and believe them all to have had an eolian origin.