The Hawai'i That Was: Exploring Pololu Valley on an Unstable "Dead" Volcano

Do the signs add a hint of an element of danger to this hike?

The stereotypical image of Hawai'i includes many things (most of which are seen in the opening credits of Hawaii Five-O), but one of them is surely the dramatic fluted cliffs clothed in tropical vegetation. It's not hard to understand why, since most tourists visit Oahu, and most of the mountains there are quite steep. The Big Island of Hawai'i is often a surprise, then, because there just aren't that many dramatic sheer cliffs. The island is composed of young shield volcanoes like Mauna Loa, Mauna Kea, or Kilauea, and shields have gentle slopes.

This is most surely not a "gentle" slope.

There is one major exception. The older shield of Kohala on the northernmost tip of the island has a twelve mile long stretch of coastline that is composed of dramatic cliffs and deep valleys. The Pololu Valley is found at the north end, while Waipi'o Valley forms the southern end.The cliffs are rugged enough that no roads penetrate the coastal wilderness. Kohala began erupting around a million years ago, with the latest flows occurring around 120,000 years ago.

Source: U.S. Geological Survey

We would expect older volcanoes to display a great deal more erosion, but that's only part of the story at Kohala. The rest of the volcano has no similar sea cliffs. Something else happened here. New technology for accurate mapping of the sea floor offshore of the Hawaiian Islands has provided a useful clue. There is chaotic debris on the ocean floor at distances reaching as much as a hundred miles. The islands have been falling apart!

It is difficult to imagine the scale of these events. The largest debris avalanche ever witnessed by humans was the one that came off the flank of Mt. St. Helens during the eruption of May 18,1980. It traveled about 12 miles. An avalanche off the side of Mt. Shasta in California traveled about 28 miles, but no one was about to see it happen, seeing as how it is more than 300,000 years old.

When the flanks of the Hawaiian Islands collapsed, the runout was more than 120 miles at Molokai, and 80 miles below the cliffs of the Pololu Coast. The sudden displacement of sea water by the rock generated devastating mega-tsunamis. One such event left chunks of coral reef 1,300 feet above sea level on the island of Lanai.

Don't worry too much about killer tsunamis on your vacation journey. As horrific as they are, they take place at intervals measured in the tens or hundreds of thousands of years, and there are no signs that any are imminent. The Pololu avalanche took place about 120,000 years ago.

A short but steep trail leads from the end of the road to the valley floor several hundred feet below. It travels farther out across the coastal cliffs providing a better view of the beach cliffs along the coast south of Pololu.

The floor of the Pololu Valley is surprisingly flat, and one might wonder that people aren't living and farming here. They once did in large numbers, but the taro fields were destroyed by a series of more "normal" tsunamis in the twentieth century, and the fields have been abandoned. There is a rich archaeological record of farming and housing sites all along the valley.

They collected rocks too. Not for their intrinsic beauty, mind you, but to construct an impressive heiau at Pu'ukoholā on the other side of the volcano, more than twenty miles away. Heiaus are large temple sites composed of hundreds of thousands of boulders that were passed hand-to-hand between thousands of "volunteers" working for King Kamehameha in the late 1700s. The workers could face punishment for dropping a stone and breaking up the rhythm of the line.

The beach is composed of black and gray sand. There is also a system of sand dunes higher up the beach. Dunes are relatively rare on the islands, but wind blew coastal sands into a series of dunes reaching an elevation of 100 feet. Enjoy the pools, beach and dunes, because the hike up is quite steep.

Waipi'o Valley along the Kohala Coast

We weren't able to stop at the valley on the other end of the Kohala Coast, but Waipi'o Valley is very much worth a visit if you are on the Big Island. There are some stunningly high water falls in the upper valley.

A Most Misunderstood Island: One of the Most Diverse Landscapes on Earth

Shall we start with a stereotypical Hawaiian beach?

One can certainly be forgiven for thinking that Hawai'i is a group of high-rise hotels next to a wide sandy beach. It isn't as if a string of television shows (Magnum, P.I. and Hawaii 5-0 for example) have spent decades putting that stereotype into our heads. And the majority of tourists never venture beyond the hotel row at Waikiki and Honolulu. A visit to some of the other islands can be a real revelation (and adventure). The Hawaiian Islands, and especially the Big Island, are one of the most diverse landscapes on planet Earth.

The view from Pu'u Huluhulu at Saddle Road summit

Not convinced? Here is a selection of pictures taken over just two days of reconnaissance on the Big Island. How about an African savanna? A lone Koa tree (I think, I'm still learning these!) overlooks the plains along the summit of Saddle Road, a highway that links the two sides of the island. There are even grazing cattle, sheep, pigs, and goats (which are doing terrible things to the natural ecosystems).

Perhaps an archaeological site in the wilds of the Sinai Desert? The great heiaus on the Big Island served a variety of purposes, including refuges, sacrificial sites, and temples. They date back hundreds of years. This one can be seen at Pu'ukohola Heiau National Historical Site on the dry side of the island in the rain shadow of the Kohala volcano. Rainfall averages less than 20 inches a year, compared to more than a hundred just a few miles away.

A recovering mesic coastal forest? Not a desert, not a rainforest, but somewhere in-between (mostly on the dry side) We are looking at the Lapakahi State Historical Park on the west slope of Kohala. The original forest was cut down for a number of reasons, but humans lived in this village for hundreds of years.

How about the high plains prairie? One of the largest privately owned ranches in the United States is found on the Big Island (the Parker Ranch). The cattle graze on rich grasslands that cover some of the older volcanoes. When they reach the right age, they fly in a 747 to the mainland. As a guide to Hawaii mentions, they probably enjoy more foot room than the average tourist in coach...

 As can be seen, some of the grasslands are windy.

Big Sur on the Big Island? Sure. This Big Island is not as famed for the coastal cliffs like those in Kaua'i and Molokai, but several tens of thousands of years ago, a large part of the northern coastline of the island collapsed into the sea. It probably produced a mega-tsunami in the local islands that had run-ups amounting to hundreds of feet in elevation.The Pololu Valley and coast is stunning.

The Pololu coast is also known for the gorgeous river valleys that extend into the Kohala volcano ("gorgeous"; Did you get it?). The canyons are hundreds of feet deep, and were once even deeper, but the islands are slowly sinking and the valleys fill with sediment.

I doubt that Sauron would have ever established Mordor in a place like this. These a'a lava flows from Mauna Loa are only a few decades old, and are practically impossible to traverse. Somehow a highway got built across part of it, and there is even a strange housing complex in the immediate vicinity. The few trees are the native Ohi'a, a tree that can grow from coastal environments to as high as 10,000 feet or so. I don't believe there is another tree on the planet that can do that.

And how about glacial environments? Yes, Hawai'i had glaciers during the Ice Ages! The top of Mauna Kea was mantled with flowing ice only a few thousand years ago. There are glacial moraines, and even a small lake that is the third highest in United States. Eruptions happening in the ice produced a glassy form of basalt that was much harder than normal, so the native Hawaiians would climb to the summit of the mountain to gather the rock for tool-making.

And finally, yes, there are rainforests! Beautiful green forests filled with rare and endemic plants found nowhere else on the planet. Don't tell anyone about this, but I see scenes like this and think of the Jungle Cruise at Disneyland! But these forests are real.

There are even more ecosystems and biomes on the island that we just didn't happen to see on our short excursions. Expect to see some more as the week progresses. We've got two more weeks on the islands, and lots of exploring to do!