Mauna Kea Ice Age

Mauna Kea Ice Age Natural Area Reserve protects 3,894 acres of alpine desert and glacial landscape on the southern summit flank of Mauna Kea volcano, preserving evidence of the ice ages that placed glaciers atop this tropical mountain and the ancient Hawaiian quarry that produced the finest stone tools in the Pacific. Established in 1981 at elevations ranging from 10,000 to 12,500 feet, the reserve encompasses a stark, otherworldly landscape of cinder cones, glacial moraines, and barren lava fields that stands in dramatic contrast to the lush tropical environments found at lower elevations on the same mountain. The reserve contains two features of exceptional significance: Lake Waiau, Hawaii's only alpine lake, and the Mauna Kea Adze Quarry, designated a National Historic Landmark as the largest primitive stone quarry in the world. This is one of the most unusual natural areas in all of Hawaii, where the evidence of ice age glaciation in the tropics intersects with one of the most important archaeological sites in Polynesia.

The alpine desert environment of the reserve supports a remarkably specialized invertebrate community, most notably the endangered wekiu bug, a unique species of seed bug found only on the summit cinder cones of Mauna Kea that feeds on wind-blown insects carried up from lower elevations and deposited on the barren summit. The aeolian ecosystem of the summit area represents one of the most extreme biological communities in Hawaii, where organisms survive in an environment characterized by intense ultraviolet radiation, extreme temperature fluctuations, negligible rainfall, and virtually no soil or vegetation. No native terrestrial mammals or birds regularly inhabit the reserve at these extreme elevations, though Hawaiian petrels may occasionally fly over the summit area during their nocturnal foraging flights. The harsh conditions and isolation of the alpine desert create an environment that functions as an ecological island within an island, harboring endemic species found nowhere else on Earth.

Vegetation within the reserve is extremely sparse, limited to scattered native silversword plants, small alpine shrubs, lichens, and mosses that represent the upper limits of plant survival on Mauna Kea at elevations above the tree line. The Mauna Kea silversword, a relative of the more famous Haleakala silversword, was historically found in the alpine zone but has been nearly eliminated by browsing feral sheep and goats, and recovery efforts continue as ungulate control measures take effect. Lichens and cryptogamic crusts growing on the cinder and rock surfaces play important ecological roles in this environment by fixing nitrogen, trapping moisture, and initiating the slow process of soil formation on the barren volcanic surfaces. The extreme aridity, intense UV radiation, and temperature fluctuations that can span from below freezing at night to well above 50 degrees Fahrenheit during the day create conditions that only the most specialized and resilient plant species can survive.

The reserve preserves exceptional evidence of Pleistocene glaciation in the tropics, including glacial moraines, striations on bedrock surfaces, and erratic boulders deposited by glaciers that covered Mauna Kea's summit during at least four major glacial advances over the past 200,000 years. During the last glacial maximum approximately 20,000 years ago, an ice cap covering roughly 27 square miles sat atop Mauna Kea, extending down to approximately 11,500 feet elevation and carving the distinctive U-shaped valleys and polished rock surfaces still visible today. The cinder cone Puu Pohaku contains one of the rarest geological phenomena in the tropics, a small area of permafrost persisting at approximately 13,000 feet elevation where ground temperatures remain below freezing year-round despite the tropical latitude. Lake Waiau, nestled in a glacially carved depression at approximately 13,020 feet, is sustained by permafrost beneath its bed that prevents water from percolating into the porous volcanic rock, making it one of the highest lakes in the Pacific Basin.

The summit region of Mauna Kea experiences a cold, arid alpine climate with temperatures that regularly drop below freezing at night and rarely exceed 50 degrees Fahrenheit even on the warmest days, with annual precipitation of only 15 to 20 inches falling primarily as snow during winter months. The thin atmosphere at nearly 14,000 feet contains approximately 40 percent less oxygen than sea level, and the reduced air pressure combined with intense unfiltered ultraviolet radiation creates challenging conditions for visitors unaccustomed to high altitude. Humidity is extremely low, and the dry air combined with strong winds can cause rapid dehydration and severe sunburn. Winter storms can deposit several feet of snow on the summit, occasionally rendering access roads impassable, and the intersection of the cold summit conditions with warmer lower-elevation air masses creates dramatic cloud formations that typically form below the summit, giving visitors the experience of being above the clouds.

The Mauna Kea Adze Quarry, known in Hawaiian as Keanakakoi or the adze-making cave, represents perhaps the most significant archaeological site in Polynesia, a massive industrial-scale quarry where Native Hawaiians extracted exceptionally dense, fine-grained basalt to manufacture stone tools prized throughout the Hawaiian Islands. Radiocarbon dating indicates that quarrying activity began by approximately 1000 CE and intensified after 1400 CE, with thousands of Hawaiian craftsmen making the arduous climb to the summit region to extract the superior-quality basalt found in certain lava flows exposed by glacial erosion. The tools produced here were traded across the Hawaiian archipelago and were preferred for their exceptional hardness and ability to hold a sharp edge, making them essential for canoe building, temple construction, and food preparation. Lake Waiau held deep spiritual significance for Native Hawaiians, who considered it the piko or umbilical connection to the heavens, and continue to conduct cultural practices at the lake today.

The Mauna Kea Ice Age Natural Area Reserve was established in 1981 under Hawaii's Natural Area Reserve System to protect the unique combination of glacial geology, alpine desert ecology, and archaeological resources found on the upper slopes of Mauna Kea. The Mauna Kea Adze Quarry was recognized as a National Historic Landmark in 1962, one of the earliest such designations in Hawaii, acknowledging its exceptional significance in understanding prehistoric Polynesian technology and trade networks. The reserve exists alongside the astronomical observatories on the summit of Mauna Kea, creating an unusual juxtaposition of ancient human endeavor and cutting-edge science on the same mountain, though the observatory development has been a source of ongoing cultural and environmental controversy. Management of the reserve involves balancing protection of the fragile alpine environment and sacred cultural sites with appropriate public access, scientific research, and the operational needs of the observatory complex.

The Humuula Trail to Mauna Kea Summit is the primary hiking route through the reserve, covering 12.8 miles round trip with an elevation gain of nearly 5,000 feet from the trailhead at the Onizuka Visitor Information Station at 9,200 feet to the 13,796-foot summit, making it one of the most challenging day hikes in Hawaii. Lake Waiau, Hawaii's only alpine lake, sits in a small glacially carved basin at approximately 13,020 feet and is reached by a short side trail from the main summit access road, offering a contemplative natural feature with deep cultural significance to Native Hawaiians. The Mauna Kea Adze Quarry, visible as extensive areas of worked stone and debitage scattered across the upper slopes, provides tangible evidence of the industrial-scale stone tool production that made this site the most important quarry in the Pacific Islands. The summit itself offers some of the finest astronomical viewing conditions on Earth, and sunset viewing from the Mauna Kea Access Road at approximately 12,000 feet is a popular activity that showcases the spectacular above-the-clouds perspective unique to this high-altitude environment.

The reserve is accessed from Saddle Road via the Mauna Kea Access Road, with the Onizuka Visitor Information Station at 9,200 feet serving as the primary gathering point where visitors are advised to spend at least 30 minutes acclimatizing before continuing to higher elevations. The access road above the visitor station is unpaved and requires a four-wheel-drive vehicle with low-range capability, and rental car companies typically prohibit driving on this road, creating logistical challenges for visitors without appropriate vehicles. The reserve is open year-round with no entrance fee or permit required for groups of fewer than ten people, though weather and road conditions can restrict access during winter months when snow and ice are present. Visitors should be prepared for altitude sickness symptoms including headache, nausea, and shortness of breath, and those with heart or respiratory conditions are advised to consult a physician before visiting elevations above 10,000 feet.

The fragile alpine desert ecosystem of the reserve is exceptionally vulnerable to disturbance, as the sparse vegetation and thin soils recover extremely slowly from damage at these high elevations where growing conditions are marginal. Invasive species including feral sheep, mouflon sheep, and goats have caused severe damage to the native alpine plant communities, particularly the critically endangered Mauna Kea silversword, and ungulate exclusion fencing and population control programs are ongoing management priorities. The development and operation of astronomical observatories on the summit has generated significant controversy regarding cultural impacts to a mountain considered sacred by many Native Hawaiians, environmental effects on the alpine ecosystem, and the appropriate level of development in a natural area reserve. Climate change poses long-term threats to the reserve's unique features, including the potential loss of summit permafrost that sustains Lake Waiau, shifts in the distribution of the specialized invertebrate communities, and reduced snow accumulation that affects the mountain's hydrology and contributes to the cultural landscape.