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Alpine Summit Scoria Zone:

Mauna Kea, Hawaii
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The summit of Mauna Kea is situated in the ahupua‘a (traditional land division) of Ka‘ohe. Nearly 3,895 acres of Mauna Kea’s upper southern flank was designated as the Mauna Kea Ice Age Natural Area Reserve by the State of Hawai‘i in 1981. Deposits of two Pleistocene glacial episodes (200,000-130,000 years ago and 80,000- 10,000 years ago) are found here. Some of the summit eruptions occurred during glacial times, and there is ample evidence of lava-ice and lava-water interaction. The rapid chilling of lava flows against ice is the geological explana- tion for the fine-grained rock prized by Hawaiians for adzes. In addition to the glacial deposits, the summit con- sists of scoria cones – formed as lava was flung skyward by escaping, expanding gas, to fall back as scoria, bombs, and spatter – and lava flows. Scoria – also called cinder – is volcanic rock that contains many gas bubbles, or vesicles. A small lake, Waiau, sits at an elevation of 13,000 feet, and its base may be a year-round layer of permafrost or an impermeable layer of fine volcanic ash.
At the summit, winds gust up to 70 miles per hour, swirling thin air with half the oxygen of sea level. In spite of nightly freezing temperatures and intense ultraviolet radi- ation, patches of leafy lichens and mosses dot this aeolian (influenced by the wind) ecosystem. The alpine summit zone is inhabited full time by at least 12 cold-hardy native insects and other arthropods (invertebrates with jointed legs). They include the day-flying Agrotis moths and omniv- orous cutworm caterpillars, voracious Lycosa wolf spiders, centipedes (Lithobius species) that prey on insects and their kin, and springtails (Entomobrya kea), tiny insects that jump using special spring apparatuses on their tails.

The unique, flightless wëkiu bug (Nysius wekiuicola), was discovered by Francis G. Howarth, Steven Lee Montgomery, and William P. Mull in 1979 on the summit cone and a few other pu‘u with concentrated aerial insect fallout. “Wëkiu” (pronounced “WHEY-cue” or “VEH-cue”) means “summit” in Hawaiian. This mini predator – about the size of a grain of rice – is dependent on fresh insects blown up the mountain from lower elevations. It hunts for prey lodged in scoria and crevices, and waits along the edges of snowmelt for its meals. Lab studies with wëkiu in controlled freezers revealed an amazing blood chemistry that kept them from freezing until 1.4°F. A sister species, Nysius a‘a, which also sucks blood from insect waifs, is found only on Mauna Loa.
Construction of roads, parking lots, and facilities associ- ated with astronomy at the summit of Mauna Kea have resulted in the loss of habitat for native summit creatures, and continues to threaten the fragile summit ecosystem. Chemicals, wastewater, and construction debris pose addi- tional threats if not disposed of properly. Undisturbed scoria

– the preferred substrate of the wëkiu bug and other Mauna Kea arthropods – can be crushed by foot and vehicular traffic. Scoria cones on the summit and upper slopes, once pristine, now bear the scars of illegal, off-road, recreational vehicle use. The wëkiu is a candidate endangered species and the subject of a citizens’ petition for listing with critical habitat designation under the Endangered Species Act.

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