The trip to Pu'u Huluhulu by itself is a 5 star rating, but we went the entire length of the Napau Trail so I dropped it to a 4 star. A group of us went in July 2012 after a Mauna Loa Summit venture and enjoyed this hike more. The trail takes off from a side road/parking area just off the Chain of Craters road (turn off is about 3.5 miles along the CoCR. We dropped a car down the CoCR at the Kealakomo Overlook where the Napau Trail comes out. Get a park map!
The walk out to Pu'u Huluhulu is easy and is appropriate for families. The trail skirts the edge of the lava flow and has several features both geologic and biological to keep you interested. You hike over to a heavily forested Hill (Pu'u) and the trail up is semi-aerobic but the vegetation is different (more varied than the scattered Ohia on the edge of the lava field). The view from the top is fascinating with a heavily vegetated mini-crater inside Pu'u Huluhulu itself. The steep outside walls are also heavily vegetated. A view out to the east is equally awesome. It looks out at Mauna Ulu (3200' elevation) which was the source of all the lava in this huge volcanic field. From the top of Pu'u Huluhulu as you look to Mauna Ulu you can't help but notice a large semi-sunken flat area which was the site of a lava lake much like Kilauea Iki but smaller and on a hillside.
Our group of experienced hikers took the Mauna Ulu trail (not necessarily family friendly after a while) that branched off at the base of Pu'u Huluhulu. It continues out and around Pu'u Huluhulu and crosses the rise between it and Mauna Ulu. Very difficult to see the lava lake so I took a side trip up to the lip of the lake. Easy going as the lava that poured out left very smooth but brittle pahoehoe slides to walk up. The back side of Mauna Ulu was filled with lava trenches, smooth river beds for the lava to flow through. Lots of cool geology stuff to keep a rock junkie happy! As we followed the Ahu (rock cairns) that mark the trail - some easy route finding kept your interest and your eyes up and looking at features. At the top of the eastern ridge of Mauna Ulu we entered an area that was still steaming with rusty red colored vents. This was the main vent system for Mauan Ulu and this area had more Aa (rough jagged lava) that demanded that you watch your footing - indeed you must have good solid well-broken in footware. We continued over extreme volcanic area to the trail junction at Makaopuhi Crater (5 miles from trailhead). This forested edge of an older crater and its sloping rise up kept it from being covered in the most recent flows. The edge of the large Makaopuhi Crater also had steam vents, etc. We walked a forested 2 miles down to the Napau Trail junction. we went east a mile or so to hopefully break out of the trees for a view of Pu'u Oo and the currently active area but turned back as we felt time pressure (not wanting to search for rock cairns in the dark). It was another forested 1.2 miles to the Naulu Trail/ Kalapana Trail junction. This was more of a path than trail but was easy to follow. At the Kalapana trail Junction it was another 2.0 miles out to the Kealakomo Overlook and our rental car. It was interesting that on the final leg of the hike, we were constantly moving in and out of the old road that had been covered periodically with lava. Great as a through put type hike, awesome geological features. Foot weary by the end but perfect to build the appetite for a restaurant stop on the drive back...
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