H. T. Stearns analyzed carefully all the supporting evidence and objections to the various viewpoints.[18] Of all of his profession, he made the most thorough field surveys, with the conclusion that the “crater” is chiefly erosional, affected by the recession of two great amphitheater-headed valleys, instead of by collapse, sliding away of the side of a cone, or explosion. Small craters may have existed at the time, but not a large one resembling the present depression. He believed that the big size results from the fact that the heads were offset and not in a straight line. The shape of the depression is what would result upon the fusion of two amphitheater heads similar to those of Waikoi, Kipahulu, and Manawainui valleys of today. Each of these is a typical Hawaiian valley, narrow at the base, but with a broad amphitheater at the head. Kipahulu is separated from Waihoi and from Kaupo Valleys by narrow divides. It can be assumed that a similar divide once separated the amphitheaters at the heads of the early Kaupo and Keanae drainages. Stearns further believes that once the rift zone was reached, stream erosion was greatly accelerated because of the loosely knit structure, the presence of many weak cinder cones, and the dike complex. This complex, as in other places in Hawaii, must have yielded perennial spring water to accelerate erosion. His summary is as follows:
“No stratigraphic or constructural evidence was found to support the hypothesis that Haleakala Crater is a true caldera, that it was formed by renting, or that Keanae and Kaupo valleys tapping this depression are grabens. Instead, detailed mapping and the examination of water tunnels show that Haleakala dome has been eroded by a number of great valleys. The hypothesis is presented that the so-called “crater” of Haleakala is chiefly, if not entirely, the result of the coalescence of the amphitheater heads of Kaupo and Keanae valleys and that renewed volcanic activity has partly masked their former divide and partly filled these valleys with lava flows.”
HALEAKALA PLANTS
Haleakala rises above the belt of warm trade winds into the cold, dry climate of the Alpine Zone. Temperatures at night may drop below freezing even in the warmer part of the year; the growing season is short and life is severe. The sparse plants that can live here crouch closely to the ground, diffusing or forming compact rosettes. All they have in which to grow are porous rocks and loose cinders that cannot hold moisture, lack organic matter, and do not yield a firm base for rooting. Species extending to lower elevations are here depauperate from wind and cold, although elsewhere they may attain a sturdy stature, even tree-size. Few seedlings are seen; individuals whose life span has finished remain conspicuous in death. Neither trees nor mats of shrubs are seen, but mosses and lichens find this Alpine desert to their liking. Oddly enough, one looks in vain for brilliant blossoms, such as one has come to expect in the high Sierra and the Rockies. The summit is a biological island on an oceanic island which, geological evidence indicates, never was part of a continent. The Hawaiian Chain was never near land of appreciable height and size.
How the Alpine plants came to Hawaii is uncertain since they have descended from ancestors so remote that past relationships are vague. The great Swedish botanist, Carl Skottsberg, believes that they are derived from a flora that grew on summits higher than any that exist today. Such assumption adds to the problem, as little else leads one to believe that elevations ever significantly exceeded 14,000 feet, i.e., the highest that exist today. In a report for the Fifth International Botanical Congress (Proceedings, pp. 91-97, Cambridge, 1931), Skottsberg listed 13 species found exclusively in the Alpine Zone, all of which are endemic, native to no other place than Hawaii’s highest volcanoes. Three other species listed as occurring in the Alpine Zone extend their range downward into the next lower Subalpine Zone, for which he has listed a total of 23 species, 20 of which he labels endemic. These adjoining zones are not sharply delimited, but blend into each other at 9,000 feet.
As elevation decreases and conditions for growth become better, the number of plant species increases. The Subalpine Zone with lower limits just above the park entrance has some of the most interesting plants found in the islands. Trees are absent but some of its shrubs extend their range to lower elevations and grow big, sometimes even to tree-size. Most Subalpine plants have small leaves or leaflets, indicating that lasting moisture is still scant. Occasional snowfall seldom remains long and never piles into drifts, which would conserve moisture.
Most of the interior of the crater is bare or thinly covered with vegetation. The uncongenial climate of the summit spills into it and extends throughout its length, though the elevation is much lower. Extensive aa flows, ash, and cinder cones cover the floor. Yet the crater has perhaps become best known through the presence of one of its plants, the silversword. Also, the lips of Koolau and Kaupo Gaps are botanically distinctive in contrast to the barreness elsewhere. This results from the fog and rain that sweep through them in late morning, only to dissolve upon mixing with the warmer air inside. As the day progresses, clouds push further and further inward, until, rarely, the whole depression may become filled. Koolau especially is a treasure-trove for the plant-lover. Below 6,000 feet, quite outside the park, it becomes impenetrable jungle surpassed only by that in Kipahulu Valley, a few miles east. Kaupo Cap is comparatively dry, but it supports a sparse scrub cover of great interest. The lower parts of Kaupo Valley are grazing land. Paliku is the only place within the park in which vegetation is lush. As it climbs Leleiwi Pali, Halemauu Trail is bordered by OHELO and ferns, among them AMAUMAU which is pleasing to the weary hiker’s eye.
In the northwestern angle of the park not far from the inn, Nianiau Crater has had a renowned floral character and history. Today it is overgrazed and drab. Dr. Joseph Rock, Hawaii’s famed dendrologist, discovered a curious tree lobelia, Clermontia haleakalensis, growing within it. He happily described the plant as “antediluvian in appearance.” This most primitive member of a distinctive Hawaiian floral group had a robust trunk from which clumsy, stubby branches shot off, each crowned with a feather-duster of long, thick, strap-shaped leaves like some pompous dictator’s headdress. MAMANE and AKALA grew thickly around it; rarer associates included tree geraniums, Neurophyllodes sp., with flowers like violets, tree Railliardia, shrubby Hawaiian buttercups, and greensword, Argyroxiphium virescens, that is threatened with extermination by grazing to an extent greater than of its relative, the silversword.
BISHOP MUSEUM, J. F. ROCK COLLECTION
Clermontia Haleakalensis.