Mauna Ulu Hike
Mauna Ulu is possibly the youngest mountain I've ever hiked.

The Mauna Ulu hike is one of the more secluded trails within the popular Hawai'i Volcanoes National Park. After hiking Mauna Kea, the island's highest peak, I decided to visit the National Park, expecting it to be crowded. As anticipated, Kīlauea and the nearby Kīlauea Iki Crater were bustling with visitors. In contrast, the Nāpau Trail to Mauna Ulu, including the Pu'u Huluhulu Crater and the Makeopuhi Crater, was remarkably quiet, virtually empty of crowds. In fact, the only other people encountered were those on helicopter tours flying overhead.

Mauna Ulu Hike: Directions and Overview

Getting to the trailhead is straightforward. The Hawai'i Volcanoes National Park has a single entrance, accessible via the main road known as the Chain of Craters. Upon arrival, a $30 entrance fee is required at the front gate. Once inside, take the first left after passing the entrance station and continue along Chain of Craters Road for approximately 7.2 miles. This scenic route leads you past well-known hikes, including the Lava Tube, Kīlauea Iki Crater, and various overlooks. The trailhead is easily identifiable with clear signage. Parking posed no issues during my visit, and there were only a handful of other visitors.

The hike I did was a combination of trails. A direct out-and-back to Mauna Ulu and Pu'u Huluhulu Crater spans between 2.5 to 3 miles, depending on your preference for proximity to Mauna Ulu. Going further on the Nāpau Trail past Mauna Ulu lead to an incredible backcountry full of new lava flows and jungles. I highly recommend going all the way to Makeopuhi Crater or even to the Nāpau Crater.

Here's my map-

And here's the distance and elevation profile-

Mauna Ulu hike to the Makeopuhi Crater

My hike was 10.9 miles with about 1,200' of elevation gain. The trail descends to the Makeopuhi Crater making it a more arduous return journey. The hike took me about 4 hours with plenty of stops for photos.

Trip Report/Field Notes

Trailhead to Pu'u Huluhulu Crater and Mauna Ulu

Starting at the parking area, I followed the well-trodden Nāpau Crater Trail for 1.1 miles to the junction of the Pu'u Huluhulu Crater. The short but steep side trail to the rim of the Pu'u Huluhulu Crater was worth the extra effort. In contrast to Mauna Ulu, the Pu'u Huluhulu Crater is densely forested and teeming with birds. The arena-shaped crater amplified the sounds of tropical birds phenomenally.

Pu'u Huluhulu Crater
The trail meanders between a barren moonscape of lava and dense tropical rainforests

Back down the trail from Pu'u Huluhulu Crater, I turned towards the more massive and looming Mauna Ulu to the south. The trail was very ambiguous past the Pu'u Huluhulu Crater given the lava flows. On the way I came across the more infamous tree molds which make the trail well-regarded.

Ascending Maun Ulu wasn't particularly arduous but I stayed well back from the crater's rim. The summit offered an exceptional view of the many relatively recent lava flows of the area. This must be the youngest mountain I've ever hiked.

Mauna Ulu Hike
Crater views

Mauna Ulu to Makaopuhi Crater

Back down on the Nāpau trail, I decided to hike the additional 3.2 miles between Mauna Ulu and the Makaopuhi Crater. This section of trail descends about 500' and deep into the wilderness designated area of the park. The trail is vague and hard to follow- occasional cairns mark the way. I got off trail several times without realizing it.

Though the trail was mostly in open, barren lava flows, it was hardly bland. About 1.2 miles from Mauna Ulu, I climbed a small rise known as Alae Crater. It was quite active with fumaroles and their characteristic wisps of white steam. At one point the rocks I hiked over were warm enough to be felt through my shoes. Volcanic activity is far from over in Volcanoes National Park.

Mauna Ulu Hike
Alea Crater's many fumaroles
A fumarole vent right on the trail warmed my feet

On I went to the rim of Makaopuhi Crater. The trail undulated over the lava until the crater's rim. In stark contrast to the former 3 miles, the crater's rim was densely forested by impenetrable jungle. It added a nice touch and variability to the hike. Once again the air was filled with innumerable tropical birds. Hawai'i at its finest.

After roughly 5.9 miles of hiking, I reached the junction of the Nāpau Trail and the Nāpau Crater Trail. This served as a good turnaround point.

Makaopuhi Crater Hike
Makaopuhi Crater rim
Makaopuhi Crater hike
Makaopuhi Crater - the largest on this hike

On the return, just prior to the trailhead, I took the short detour to the Mauna Ulu eruption flows. Lava waves and curious formations dotted the landscape.

As a parting gift, I spotted a pair of Nēnēs by the parking lot just before departing

Mauna Ulu Hike
Nēnēs by the Mauna Ulu trailhead