Geological and Topographical Report Upon Nihoa, or Bird Island.
Surveyed July 22, 1885, by Sereno E. Bishop.
Hon. W. D. Alexander, Surveyor-General of the Hawaiian Kingdom:
Sir: I was employed by you to proceed with the excursion party of H. R. H. Princess Liliuokalani, Mr. Jaeger and others, to Nihoa, or Bird Island, per steamer Iwalani, and make such topographical survey thereof as circumstances should allow, also to observe the geology of the island.
We sailed from Honolulu on Monday, July 20th, with a large company of excursionists, chiefly Hawaiians, including the Princess and her attendants, and His Ex. J. M. Kapena and family; also, Messrs. Jaeger, Williams, Hall and Dole, the latter of whom made special observations of the birds, which are the sole inhabitants of Nihoa.
At Kauai our company was increased by the addition of Gov. P. Kanoa, Mr. Deverell, with a superior photographic apparatus, and Mr.Rowell, who aided in the survey. At 5 o’clock p. m., on the 22d, passing the “barking sands” of Mana, our course was laid W.N.W. half W., steaming about nine knots, with a fair but moderate wind. Slowed at 3 o’clock a. m. to five knots, but pushed on at 4:30, shortly after which Nihoa was seen bearing W.S.W., twenty miles distant. Bore down directly for its N.W. point, and by 7 o’clock a. m. were close under its immense northern precipice and pinnacles. Many myriads of birds were swarming around the island and the ship. Mr. Williams obtained an excellent photograph, showing especially the N. and E. precipices, and the white streaking thereon of guano. A cave or tunnel, through which boats can pass, of 500 feet length underlies a S.E. promontory. We saw through this tunnel from both sides. Every cranny and ledge of the northern precipice appeared to be packed with the nests of birds, conspicuously the large downy young of the frigate-bird. The greater part of this precipice—4,000 feet long, 300 feet high in the middle, and rising to 900 feet at each end,is either absolutely perpendicular, or sensibly overhangs, so that at several points a pebble may be dropped plumb into the waves. This very exceptional for of precipice appears to be due to a quite uniform structure of compact scoriaceous layers thoroughly cemented, its erosion being almost wholly from the waves at its base. Although much lighter and softer than the basaltic forms of lava, this scoriaceous or clinker lava holds its place as long as anything is at all underneath it, whereas the usual strata of columnar basalt with underlying loose soil and cavities, are incapable of perpendicular erosion. Its precipices are usually at a considerable angle, while the scoriaceous centers of our older and much eroded volcanic mountains abound in sharp ridges and pinnacles.
As we approached the N.W. angle, there became conspicuous a very large number of perpendicular basaltic dikes, more than I have ever before seen in an equal space. These traversed the whole island from end to end, in many places erecting their hard sharp crests above the general surface. They were from two feet to perhaps ten in thickness. They were substantially parallel with each other. Their general direction was east and west.
The north and west precipices form a sharp and very perfect acute angle. The sudden opening of the view of the western wall was very impressive. The upper edge of that wall is strangely jagged, a succession of ragged pinnacles for 3,200 feet declining to a low, long promontory, bending around to enclose a deep cove with a fine sand beach, which unfortunately opens to the S.E. and the force of the trades, which produce a heavy surf. Swiftly rounding the point, we anchored in front of this and two other coves somewhat protected by a projecting cliff to the S.E. These coves are formed by a series of small valleys and ridges sloping down from the high northern side and entering the sea. These gullies and ridges all point inward, precisely as do those at the head of the upper S.W. valley of Konahuanui, which is the chief source of Nuuanu stream.
The middle valley is low, nearly bisecting the island in its narrowest part, which is about 800 feet wide. Its head is the innermost and lowest part of the concavity of the north precipice, about 300 feet high, and its foot at the deepest of the three coves. The island is thus divided somewhat unequally into two lofty bulks, whose slopes incline somewhat toward each other, each presided over by a 900 foot summit.At the head of the deep middle cove Messrs. Dole and Hall found a tolerable landing place upon the ledge. This had eluded observation until too late for use.
The workers landed about 8:30 o’clock in the first boat, with some difficulty, on the ledges which are nearly continuous under the low cliffs which line the whole bay. Ascending the cliff some forty feet with difficulty, we came out upon the steep slopes. These were well covered with the sweet bunch grass known as makuikui. Its straight leaves contain a hemp-like fibre, which does not decay, but accumulates under the bunch for many years. Portions were thickly covered with ilima or sida, and other small bushes. Two small groves of palm trees were conspicuous, the chief one in the large eastern valley, the other in the central one. The entire surface was densely crowded with nests of sea birds, about 2,500 to the acre. As we emerged upon the slope the older birds rose in enormous clouds, while their helpless young remained in their nests, each with its single companion egg, which probably it aided in hatching. The smaller birds nestled in burrows under the dry bunch grass, and in the numerous caves and crannies of the rocks, while many of the larger nests were flat surfaces of twigs on small bushes beaten down and matted together, notably those of the great frigate bird [iwa].
The surface was covered with thin soil and loose brittle scoriae. The soil was gray and ashy. The stone seemed saturated with guano. The strong odor of this was very pervading everywhere. Whether a soil that will permit so much vegetation can be rich enough to pay for removal as a fertilizer I do not know, but it seems worthy of examination. There must be between 50,000 and 100,000 cubic yards of such soil and soft stone upon the slopes of Nihoa, most of which could be easily delivered by shutes into lighters moored off the low cliffs. I estimate the whole number of birds whose nests occupied the southern slopes at not less than one million, large and small, and immense numbers besides on the outer precipice.
Two stations were chosen for a base line, one about 200 feet inland on the most central ridge at the height of 207 feet, the other across the large cove on the brow of the cliff, 126 feet high. The latter station was upon a ruined terrace of stones, probably one of several house foundations which the very accurate Dr. Baldwin informs me that Kamehameha III found on Nihoa, being not far from the best landing and the chief water hole. An accurate telemeter measurement gave the horizontal length of my base at 1,168 feet, from which all my heights and distances are derived. I judge the possible error not to exceed six feet or .005. A magnetic azimuth was employed, circumstances preventing solar observations for true azimuth. The two stations differed four degrees as to the direction of the needle. The azimuth of the first station was adopted, being judged least subject to local attraction.
A quite full survey of the coves was secured by means of depression angles to the water’s edge, verified by a few intersections. Several of the most prominent peaks overhanging the outer shore were also well located by intersections, and heights determined. A large number of careful sketches, together with Mr. Williams’ excellent photograph, supply ample means for filling out the outer coast lines and the contours. An outline of the island, drawn by Mr. Rowell, from the summits, is a most valuable aid. Mr. Rowell’s aneroid measurements are quite uniformly 60 or 70 feet short of my triangulated heights. But this is fully accounted for by his acknowledged defective correction for sea level.
We were proceeding to occupy a third station above the south point, making a second base, and expecting two hours more work whereby to elaborate our survey, by the help of many flags set by Mr. Rowell on lofty points, when a fire broke out about 300 feet above my main station, and spread with great speed and force in the masses of dry tindery matter. This at once filled the island with such volumes of smoke that it became impossible to measure an angle on any flag. The last of the hundreds of people who had landed had already all disappeared below the cliffs, and were slowly embarking. We reluctantly retired from our work, and followed them. Within an hour my station had been swept by the flames, which spread in every direction.
The embarkation was much more difficult and hazardous than the landing, the sea having risen somewhat, as well as the tide. Two boats had been swamped, one of them causing the loss of most of the negatives taken on shore, and destruction of the cameras, Mr. Deverell saving his own life by extreme activity and strength. We were so happy as to get our instruments aboard safely. I believe that no person suffered any serious injury, all but a few whites being at home in such rough work. The Princess was conspicuous for her adroit and agile spring through a dangerous surge upon her whale boat as it darted up to the rocks for an instant.
The extreme length of Nihoa from W.N.W. to E.S.E. is not far from 5,200 feet. Its average width about 2,000 feet, giving an area of about 250 acres. Four-fifths of this very steep, grassy slope, the rest precipices. I did not see enough level ground to build a native hut upon without terracing. The general contours are much like those of Punchbowl towards Waikiki, save that the ridges tend inward instead of radiating outward.
The N.E. pinnacle, which overhangs, is 869 feet high, with a possible error of 10 feet. The highest N.W. pinnacle is 900 feet, with possible error of 20. Had a third station been occupied, the element of error would have been minimized. I trust shortly to submit to you a finished map of the island.
In respect to the geology of Nihoa, I regard the evidence as complete and conclusive, that it is the small remaining portion of an extremely eroded and deeply submerged volcanic dome homologous with the larger islands of the Hawaiian group which still survive in their various stages of present upbuilding, recent extinction of volcanic activity, less or more advanced erosion, and slighter or deeper subsidence. I would not place undue stress on the very obvious fact of progressive extinction from N.W. to S.E., nor of apparently deeper subsidence progressing in the same direction, nor of Nihoa being equidistant with the other main volcanic centers of the chain, all which would lead us to look to the site of Nihoa for a volcanic center still more ancient than Kauai.
For positive evidence we must take the form and structure of the island itself. In the first place, the substance of the island is homogeneous with the substance composing the central interior portions of Oahu and Maui, as seen in their inner ridges and pinnacles where the deepest erosions have most thoroughly eaten down to the hearts of their ancient domes. I have uniformily found those interior formations not basaltic, but scoriaceous. It appears that during the period of upbuilding, clinkery and scoriaceous ejecta pile up at the center of the volcanic dome and form its core, while the outflowing streams of lava build up its circumference in layers of more or less basaltic formation. Nihoa seems to be a pair of clinkery pinnacles out of the inner core of a once mighty dome which has been eaten down by winds and rains for thousands of feet, and during unreckoned ages.
But the conclusive evidence in my view is the presence of the numerous parallel basaltic dikes, which, as stated above, cut the island from end to end and from summit to base. Such dikes can only be produced by lava during an eruption, rising and filling thin fissures such as an earthquake might produce across the mass of the dome. Possibly each dike may be the work of a separate eruption of the volcano. At any rate a great period must have elapsed between the slow piling up of the successive irregular strata of scoriae, and the later splitting and diking of the whole mass.
Such dikes I have found as a characteristic accompaniment of the interior scoriaceous cores of our mountains. Many persons must have observed the very fine specimen of a basaltic dike intersecting the road down the Nuuanu pali. Some splendid specimens cut obliquely across the inner scoria piles of Olowalu and Ukumehame canyons on West Maui, striking in parallel lines undeviatingly across ridge and chasm, and rearing sharp crests above the heights. Some of our Nihoa party may remember a succession of high ridged perpendicular steps on the main left hand slope. Those were the lower faces of several parallel dikes cutting across the ridge.
From the great number of these dikes, I infer a very protracted period of volcanic activity. From the closeness with which they stand, perhaps forty or fifty cutting across the island, I infer that we are looking far down in the deep heart of the former dome, where dikes would be thickest.
As to probable subsidence, something may be inferred from the fact that all outlying peaks and ridges have disappeared from what the presence of the sharp, hard, thick-set dikes proves to have been once a dome of considerable extent at least. Nihoa seems to be the sole submerged pinnacle.
The peculiar contour of the ridges running down towards each other seems very significant. This is precisely the contour of the head of the leeward valleys descending from the peaks on either side of Nuuanu Valley. It is the amphitheater form which Captain Dutton shows to be the natural evolution of the heads of ravines of atmospheric erosion.
Take the top of Konahuanui; sink it slowly to within 900 feet of its twin summits. Let the waves meantime be eating away the bases of its extremely steep Koolau, Nuuanu and Manoa sides, until they become perpendicular, while sloping southwestern valley is defended from the sea by its protecting side ridges. In the course of the ages Konahuanui has become the somewhat smaller, but very exact counterpart of Nihoa in every particular, both of position, contour and structure.
Sailing from Nihoa at 4 p. m., we made the small island of Kaula, twenty miles southwest of Niihau, at 7 a. m., and spent two hours and more in making the circuit of the island and landing a party in pursuit of the birds which swarmed much as at Nihoa. Kaula is a beautiful specimen of the cinder-cone, about the size and form of Punchbowl cut in half, the lower and windward half destroyed by the waves. Its beautiful compact laminated strata of true, yellow cinder showed the rounded “onion-skin” form admirably, much like the sea face of the lower Koko Head. The contrast with the irregular but quite horizontal strata of Nihoa’s gray and black scoriae was most marked. Lehua, which we skirted in the afternoon, exhibited a formation similar to Kaula, but maintaining about 200 degrees of its circle, instead of the 140 degrees of the latter. The lamination on the south incline of the higher part is exquisite. Both these crater cones of Lehua follow the common law of all such formations in these islands, that their highest side is to the west, whither the prevailing trade wind usually pushes the falling rain of ashes and lapili during the brief explosion, building up to leeward a compact laminated pile of the ejecta, while the windward side is low, and if exposed to the waves, soon washed away, leaving a crescent form like Lehua, Kaula and Molokini opening to the winds and surges.
In contrast with this law of the cinder-cones, and in accordance with the prevailing law of our older and deeply eroded ridges and pinnacles, Nihoa presents its high and perpendicular side to the wind, and its sloping and indented side to the leeward, as does Konahuanui.
Evidences of a slight recent elevation, following a long period of subsidence, are quite marked on Oahu, and I think on Kauai and perhaps Niihau. I therefore looked for evidence of such possible recent elevation at Nihoa, but discovered none whatever. Such tokens, however, must easily elude observation on so precipitous and unsheltered a shore. Very respectfully,
Sereno E. Bishop
Honolulu, July 31, 1885.
(PCA, 8/6/1885, p. 3)