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Mauna Ulu, or growing mountain is a tall, sloping, shield-shaped hill formed by numerous eruptions along the rift between 1969 and 1974; Mauna Ulu is best seen by walking a few yards past the road beyond the parking lot to where the end of road is covered in fresh lava flows. At Mauna Ulu, visitors can get an intimate look at both pahoehoe and aa lava flow types. Pahoehoe, the less viscous and generally hotter liquid flow, moves fluidly like a river or glacier, the surface folding and molding, like poured taffy, into a ropy structure. Pahoehoe forms generally flat, fairly smooth, hard surfaces. Aa, on the other hand, is much cooler and has exolved much of its dissolved gas, so it is much more viscous, causing the upper surface to fracture into clinker-like boulders and fragments. Flowing aa sounds and looks like a moving pile of hot glass shards; when it cools, it leaves behind rubbly piles of sharp fragments. Fields of pahoehoe and aa make a landscape that look as if Madame Pele has bulldozed her land to flat surfaces, but left these acres of boulder piles here and there.

Pu’u Huluhulu (shaggy hill) is a 150 foot tall cinder cone formed in pre-contact times between Mauna Ulu and Pauahi Crater. There is a fascinating 3 mile round trip hike from the Mauna Ulu parking lot to the top of Pu’u Huluhulu that is marked by cairns (or ahu). From the vantage point of Pu’u Huluhulu’s summit, one can see Pu’u O’o (hill of the bird) about 5 miles away. From Pu’u Huluhulu are fine views of Mauna Loa, Kilauea, Mauna Kea, the coastline and Pu’u O’o. Pu’u O’o is a spatter cone built by the fire-fountains erupting along Kilauea’s rift zone between 1983 and 1986. Since 1986, the center of eruption has moved about 2 miles further down the rift to a vent called Kupaianaha, or mysterious in Hawaiian. The round trip hike from Mauna Ulu Parking lot to Pu’u Huluhulu and return takes about an hour and a half to two hours.

The hike to the summit of Mauna Ulu is a long, dry, serious hike with some dangers and should only be undertaken by those in good physical condition and experienced at hiking cross-country across broken and hazardous ground.

Written and produced by Donnie MacGowan; videography by Frank Burgess and Donald MacGowan; narrated by Frank Burgess; original musical score written and performed by Donnie MacGowan.

For more information on touring Hawaii in general and visiting the Big Island in particular, please go to and


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