Hawaiian Volcanoes

Yes thatʻs right, Haleakalā is still considered an active shield volcano; you can definitely tell your friends and family back home that you hiked on an active volcano. However, it is also considered dormant, which means Haleakalā has not erupted in some time – about 400 years – but is expected to erupt in the next 500 years. We like to say that Haleakalā is taking a nap.

That seems like a pretty long “nap”, but geologically, it is a very short time window. The last eruption occurred on Haleakalāʻs southwestern flank in Keoneʻōʻio (The sandy [place with] bonefish) which is now also called La Pérouse Bay, around the year 1730.

If you drive past Makena Beach State Park on Maui’s south side, you can go check out Keoneʻōʻio, where there is some great snorkeling. Make sure to have the team at Redline Rafting take you out there! Once there, look up towards Haleakalā, where you can follow the black lava rock about halfway up the mountain where the most recent eruption came out of an old cinder cone.

Haleakalā’s summit rises 10,023 feet above the Pacific Ocean but it used to be almost 2,000 feet taller than it is now.

The Hawaiian Islands are in a constant battle between two geologic forces: erosion and volcanic activity. The newest islands (Big Island and Maui) tend to have more recent volcanic activity, which is why these islands have the tallest mountains, and a more gradual slope. The older islands have not had volcanic activity in millions of years, which is why they tend to have smaller but steeper mountains where erosion has taken more of an effect.

Haleakalā’s crater is actually not a volcanic crater or caldera. In the last 1500 years, erosion has carved out an area about 7 miles long, 2 miles wide, and nearly 3000 ft from the bottom to the top of the crater. The rate of erosion in the crater is incredibly fast for a variety of reasons. There is practically no vegetation in the crater or at the summit and because of this, there isnʻt a root system to hold all that soil together. Temperature changes within the crater can go from below freezing to up to 80 degrees in less than 24 hours, and sometimes gusts can reach 50 mph or more. Every so often, when there is a big rainstorm up there, all that water will carve out that loose sediment down into the crater. All of these factors have contributed to an extremely fast rate of erosion.

Every winter, Mauna Kea and Mauna Loa over on the Big Island get blanketed in a layer of snow. It just so happens that Haleakalā on Maui gets snow as well, only every couple of years. The presence of snow in Hawaiʻi was recognized and embodied by Poliʻahu, the goddess of snow. Her sister Lilinoe, the goddess of the mist, is said to reside in Haleakalā.