Geology of Haleakala National Park

I don’t suppose you’ll be surprised to hear that the geological history of Haleakala National Park is rather volcanic. Yep, those volcanoes have a lot to answer for, and one thing they have to answer for is the park.

The Haleakala Crater is a great reminder of how active the volcano once was. Now a cool crater with streaks of yellow, red, gray and black, traces of lava flows both ancient and recent. Volcanic rocks break away slowly as they are lashed by the forces of nature, heavy rain and winds.

The Hawaiian Islands including Maui, the home of the Haleakala National Park are simply volcanic islands, mountains raising out from the sea and forming a chain towards Japan.

Maui is one of the younger islands in the chain, beginning life as two separate volcanoes on the floor of the ocean. With the passing of time (lots of time) the volcanoes erupted and spread new, thin sheets of lava on top of the old, building layer upon layer until the heads of the volcanoes rose above the sea. The accumulation of lava, alluvium and wind blown ash joined the two islands over time and they became Maui, or “The Valley Isle”. The larger of the two volcanoes towards the east (Haleakala) grew to the enormous height of 12,000 feet above the level of the ocean, an incredible 30,000 feet from the ocean floor.

Volcanic activities ceased for a while and the islands were shaped by erosion. The height of the mountain meant that it trapped northeast tradewinds, laden with moisture, which fell as rain creating channel cutting streams down its slopes. The large depressions close to the summit were eroded by two such streams.  Eventually the valleys met creating the crater, just as a series of ice-age emergences and submergences were happening . . . thus the four younger Hawaiian islands were born.

One fascinating fact about volcanoes is that they may lie sleeping for years and then, boom, burst back into action. When the time came for volcanic activity to return once more close to the summit the lava began to pour down the valleys cut out by the streams, almost filling them. Volcanic bombs, ash and cinders blew from the vents forming cones as high as 600 feet – symmetrical and multi-colored cones. The basin which was carved out by water became filled with lava and cinder cones, truly resembling a volcanic crater.

The island of Maui hasn’t seen any volcanic activity for several hundred years, but that doesn’t mean that Haleakala won’t ever erupt again.