Haʻakulamanu (Sulphur Banks) Trail

Haʻakulamanu (Sulphur Banks) is an easy, 1.2-mile out-and-back from the west-side entrance across Crater Rim Drive from Kūkamāhuākea (Steam Vents) parking. Paved tread and a wooden boardwalk lead to an open field of steam vents and mineral-colored ground, then you return the same way. Allow 30–45 minutes. This is a close-up geology walk, not a strenuous hike or a route to a crater overlook; its appeal is seeing heat and gas working at ground level.

The accessible entrance sits across the road from Steam Vents parking. The path passes through a short stand of trees before opening onto pale, yellow and red-brown banks. Wooden boardwalk carries you beside several vents, with stretches of paved path between; the route is easy to follow and nearly level. Interpretive signs help make sense of what you are seeing. Treat the Sulphur Banks area as the destination: look around from the boardwalk, then retrace your steps. A photo that includes the boards, rising steam and colored ground shows the setting better than a close crop of sulfur alone.

Nearby Kūkamāhuākea (Steam Vents) releases water vapor after groundwater seeps down to hot rock and returns as steam. At Haʻakulamanu, water vapor rises with volcanic gases from deeper cracks. Sulfur dioxide has a sharp, struck-match smell; hydrogen sulfide smells like rotten eggs. Visitors often notice the odor, though its strength can vary. The gases are part of the geology, not just an unpleasant smell to ignore.

Some sulfur-bearing gases react to form pure yellow crystals; others make sulfuric acid that changes the lava into clay. Iron oxide stains the altered ground red and brown. In 1922, scientists drilled two holes nearby and measured 205°F (96°C) at 50 feet (15 m), the greatest depth they reached; that is an underground reading, not the temperature of the path. Visitors gave the place its English name in the early 1800s, using the British spelling Sulphur. Its Hawaiian name, kūkaepele, is glossed as “the waste of Pele.”

Park guidance says people with heart or respiratory conditions, including asthma, pregnant people, infants and young children should avoid this walk because of volcanic gases. Check air-quality information before setting out; do not use the smell alone to judge exposure. Pets are not allowed. There is no separate activity fee or reservation, but park admission applies. This is a worthwhile short stop if you want an accessible look at active volcanic deposits and signs explaining them; hikers looking for a long walk or a broad crater view may prefer another route.