back to Hawaii 2009

Summit "crater" of Haleakala; not really a crater, nor a caldera. It is an eroded valley filled with lavas of the rejuvenated stage

If the Big Island is the child and adolescent of hot spot volcanoes, and if Kaua'i is the elder of the islands, Maui is middle age. The fires of youth are not quite dead, but they are merely glowing embers now. Maui's most recent gasp of volcanic activity took place within the last few hundred years, possibly as recently as 1790, although that date is not at all confirmed. The island is, of course, an immensely popular tourist destination, but it is also a wonderful showplace of volcanic geology as well.

Maui is called the Valley Isle because it actually consists of two volcanoes with a flat intervening valley. Thousands of acres of sugar cane are still cultivated on the plains. Kahului, on the north coast, is the main town on the island, with an airport and seaport. Lahaina, on the south coast is the historical center and main tourist destination. Most of the resorts have been built along the west-facing Kihei coast, on Maalaea Bay. The population is about 140,000.

The oldest of the two volcanoes is usually referred to simply as the West Maui Volcano. It is more than two million years old, and was active until about 500,000 years ago. The high point of the volcano, Pu'u Kukui, is 5,788 feet above sea level, is apparently the second wettest place on the islands, averaging about 386 inches of rain each year. The main shield-building lavas are called the Wailuku Basalts. The later capping alkali basalts are the Honolua Basalts. It seems to be fully extinct. 

Haleakala, a much larger volcano, is about one million years old, with the main period of activity lasting until about 350,000 years ago, with an intense period of rejuvenation starting about 100,000 years before present, and presumably continuing today. The oldest shield basalts are called the Honomanu Basalts, and the capping lava flows are the Kula Volcanics. The lava flows of the rejuvenated stage are the Hana Volcanics. Haleakala is truly immense. Although it is more than 3,000 feet shorter than the Mauna Loa and Mauna Kea, it has also sunk a greater distance into the crust, and as such may have a claim as the biggest single mountain on the planet.

The grouping of the four islands, Maui, Moloka'i, Lana'i, and Kaho'olawe is intriguing. If one were to submerge the Big Island to a depth of 5,000 feet or so, one would find a similar grouping of islands.  Maui was once part of a landmass that was actually bigger than the Big Island! This land mass, now called Maui Nui reached its greatest extent about 1.2 million years ago. The islands have subsided and eroded, and sea level has risen since the ice ages, to reclaim these lands.

We spent the better part of three days on the island, with an afternoon exploration of a part of the West Maui Volcano, a full day traverse around the flanks of Haleakala to the town of Hana, and an early morning drive to the summit of the volcano.

Exploring the West Maui Volcano         Well, it was another 7 hour project to move 27 people from one island to another but we got moved in, got lunch and hit the road on a very brief exploration of the West Maui Volcano. The first stop was far more  civilized, the Maui Ocean Center. It's a nice aquarium, with a lot of local species. The story of the aquatic world of the Hawaiian Islands is as interesting as the stories of the land-based ecosystem, driven by isolation. There are many unusual endemic species. I loved these eels! The aquarium is raising Hawaiian Sea Turtles. They are a much more dynamic species when under water. Beautiful graceful underwater fliers. West Maui Volcano is considerably smaller and more deeply eroded than its neighbor across the valley. Only one road penetrates into the interior, at 'Iao Valley State Park. Although a very small park, it loads a great deal of scenery into a small space.   The valley gets a lot of rain, and it came and went as we looked around. There weren't a lot of rock exposures in this rainforest. A nice rainbow formed behind us. The peaceful setting belied a ghastly, violent history, as a horrific bloody battle was fought here in the late 1700's as King Kamehameha solidified his control over the Hawaiian Islands.    The most prominent feature in the park is 'Iao Needle, which looms over the trail and river. The name in the Hawaiian language is much more graphic, referring to a part of the male anatomy. The rock is associated with Kanaloa, the god of the oceans. I asked the students to compare and contrast the 'Iao Valley with Kilauea Caldera back on the Big Island. The resemblance is clearly not evident...   After the extinction of magmatism on West Maui Volcano, erosion began. The rocks within the ancient caldera had been altered and weathered by hot acidic water. When headward erosion breached the caldera rim, the rocks were rapidly excavated and removed, forming the deep 'Iao Valley. So, the connection to Kilauea is that on the Big Island, we were standing on top of an active caldera. Here at 'Iao Valley, we were standing underneath the caldera, which no longer exists. 'Iao Needle is the remnant of a feeder dike that once supplied lavas to surface eruptions.   It's a place that just seems to beg for further exploration. Most of the summit region of the volcano is untracked wilderness, and includes habitat for some very rare birds and plants. Parts of the summit area get rainfall amounts similar to Waialeale on Kaua'i, and at least one summit plateau has developed a sort of pseudo-karst topography complete with sinkholes, despite the fact that the rock here is basalt, not limestone. The region is privately owned by an agricultural company, but they manage the land as a wilderness and watershed resource.  Following our exploration of the valley, we headed back down to the coastal plain and to our accommodations for the night....    Our hotel offered a marvelous early morning view of the West Maui Volcano. I was too distracted with logistics to take such a nice picture...this view is courtesy of Susan Hayes.

Flanking the Volcano: the Hana Road         Our next day's travel took us on the legendary Hana Road, which winds in and out of canyons and cliffs for more than fifty miles around the north and east flanks of Haleakala.  It is considered one of the great drives on the planet, and I tend to agree (photo courtesy of Susan Hayes).  It is narrow, passes over dozens of one-lane bridges, and there is a considerable amount of traffic every morning as hundreds of tourists make the journey....(photo courtesy of Susan Hayes) Geology is a bit tricky to find on the road; every square inch of the landscape seems mantled with living greenery. This is the windward side of the island, and it rains prodigiously. Every gulch crossed by the highway seems to contain a beautiful waterfall... We did have one geological show along the way. On March 22 of  this year, part of the cliff near mile 20 collapsed and blocked the road. Although it was cleared in a few hours, it is obviously still of concern to the road maintenance crews.    I've heard of hanging around on the job, but this is ridiculous! I wasn't clear if they were trying to knock down other loose boulders, or if they were installing rock bolts to stabilize the cliff. We had about 45 minutes to contemplate their work, as they blocked traffic on the highway while they were drilling. I really can't complain though, it was good geology, and the waterfall of the previous picture was right below them. If you have to be stuck in traffic, it might as well be in paradise...   It's not a native (not with a name like African Tulip), but these trees made a splashy showing in the rainforest along the highway (photo courtesy of Susan Hayes)   Our goal for the day was to reach the O'heo Gulch. That doesn't sound like much of a destination, so many years ago, a promoter called the place the "Seven Sacred Pools", and the tourists arrived in droves. It is a series of pretty pools and small waterfalls. More recently the lands were deeded to the National Park Service, and now a section of the park extends from sea level to the summit of Haleakala at 10,023 feet.  The lower part of the canyon complex is open for visitation, but the upper valley, the Kipahulu, is one of the last stands of native species on the island of Maui, and is closed to all entry except researchers and park personnel who are removing non-native species. My carefully framed picture looking up the Kipahulu Valley was blurry, so instead I present your stimulus funds at work in the national park system. They were working hard to put in a new parking lot on the day we visited. The Kipahulu, visible on the skyline in the photo, used to be a deeper valley, but was filled with lavas during the rejuvenated stage within the last 100,000 years. The trip back was less stressful, given a huge drop in the traffic. We were able to stop a few times and look at the rainforest and the ocean (photo courtesy of Susan Hayes).   Although we couldn't see many rocks, the volcanic history of Haleakala was revealed in the topography. Rejuvenation stage lavas produced a number of coastal flats where small villages could be built. The older slopes tended to be to eroded and steep for development. The coastal cliffs revealed some of the shield lavas of Haleakala. Hana Road winds across the top of the scene (photo courtesy of Susan Hayes).   As we came back from our excursion, the sun was setting over West Maui Volcano. Those knobs on the coast are a couple of volcanic necks near Kahului (photo courtesy of Susan Hayes).