Volcanoes in Hawai'i: Rock Finds a Way (to destroy life)

The summit of Mauna Kea in the distance, and the forested lower slopes of Mauna Loa in the foreground

My last entry on the geological drama of Hawai'i concerned the stubbornness of life in a harsh volcanic environment, such as that which is found on the highest slopes of Mauna Loa and Mauna Kea on the Big Island of Hawai'i. I was echoing of course one of the memorable lines from the movie "Jurassic Park". As I started to review my next set of pictures from my recent trip, I realized the opposite supposition also holds true: rock finds a way (to kill life).

Lua Manu Crater on Chain of Craters Road. It formed by collapsing several hundred years ago, and was later filled with lava flows in 1974. 

Now obviously, it couldn't be clearer that lava destroys life as it flows through and burns forests. The aftermath of many a flow is a barren plain with no sign of life of any kind. In the tropical climate of Hawai'i, life returns quickly as wind and water aid in the propagation of seeds from the nearby forest. Sometimes it is bird droppings that scatter the seed and provide the first nutrients that lead to a rebirth of life. The surface of the Big Island gets made over repeatedly over the millennia.

The battle between rock and life does take unusual forms sometimes, which is what I wanted to illustrate in today's post. Basaltic lava is not always the all-consuming fiery hell we often take it to be. It may be in excess of 2,000 degrees Fahrenheit (1,100 degrees Celsius) as it flows from the vent, but when the lava encounters cold objects, the surface of the lava can freeze quickly. When the object is a tree, strange things can happen.

On the slopes of Kilauea or Mauna Loa, the most common tree is the Ohi'a, which I wrote of in the previous post. In 1974, the Keanakāko‘i flow overwhelmed an Ohi'a forest near Chain of Craters Road in Hawai'i Volcanoes National Park. The lava froze around the trunks as the trees themselves caught fire and burned away.

The resulting cavities are called tree molds, and they were spread widely in the Keanakāko‘i flow. The charcoal from the former tree can still be seen in some of the molds after forty years (below).

At times, the molds perfectly preserve the pattern of the bark, as can be seen below.

There is another odd phenomena that occurs in these events. The lava flows past the trees, solidifying around the trunk, and continuing on. It's not always obvious, but as lava flows by, the thickness can change, and the level of the flow can drop around the trees. The tree molds are left behind as towers of basalt with hollow centers (lava trees). It's actually kind of eerie to encounter such ghosts in the midst of a living forest (below), and easy to understand how ancient people considered these to be people turned to stone by the gods.

The 1974 has hundreds of these lava trees, and some take bizarre shapes, as in the case below, where a multiple-trunked tree (or a clump of several) was preserved.

It's obvious that life is slowly being reestablished on the flow, as we were surrounded by Ohi'a trees and other species at various stages of growth.

It turns out that the tree molds themselves offer a hospitable environment for life, with nutrients provided by the charcoal, and cooler wetter conditions below the surface.

The lava forests can be seen in several places. By far the easiest is at Lava Tree State Monument in the Pahoa area. It resulted from a flow in 1790, and the park offers paved accessible trails and interpretive signs. If you want to see the Keanakāko‘i ghost forest, you'll find it in the vicinity of Lua Manu Crater on Chain of Craters Road in Hawai'i Volcanoes National Park. There are no signs and no trails, so you are in for a bit more of a rugged adventure. Be prepared with water, sturdy shoes, and the other usual things you need for a wilderness outing. And...be careful while studying the ghost trees. Many are unstable and fragile and could be destroyed by a thoughtless climb or push. And having one fall on you can't possibly end well.

Volcanic Flows in Hawai'i: Life Finds a Way (to destroy rocks)

Ohi'a Lehua (Metrosideros polymorpha) clinging to a crack in a 1974 lava flow on Kilauea

I had kind of a schizophrenic (split-brain) response in regards to what I wanted to accomplish with this post. A couple of weeks ago while still in Hawai'i, I did a post on what I considered the ultimate wilderness on planet Earth, the nearly lifeless high-altitude basalt flows of Mauna Loa on the Big Island. At first, as a follow-up, I was thinking of the idea of how life finds a way to propagate even in the most barren settings. As I went along though, I started to think about how rock is destroyed, and how often life has something to do with the destruction. Whatever way this post decides to go, the unique Hawaiian tree Ohi'a Lehua (Metrosideros polymorpha) is going to have something to do with it.

Ohi'a Lehua (Metrosideros polymorpha). The trees are threatened by Rapid Ohia Death disease.

The Ohi'a is one of the most remarkable tree species on the planet. The Latin name polymorpha ('many shapes') provides a clue why: it can grow in a stunning number of deeply contrasting environments. Ohi'a trees can be found as the first pioneering species on fresh lava flows, as in the pictures above. They can be found on the near-desert leeward slopes of the island's volcanoes. They form the canopy of most of the island's rainforests, growing to heights approaching 100 feet (30 meters). They grow in near alpine conditions at 8,000-9,000 feet on Mauna Loa and Mauna Kea. And stunted trees, barely shrubs, survive in the high altitude bogs on Kauai where the rainfall exceeds 300 inches a year. I know of no other tree species that is capable of such feats.

It's true that you could try and cultivate Ohi'a trees in these kinds of environments elsewhere in the world and they might not do very well in competition with other established species. On Hawai'i, though, all they have to do is survive, because the isolation of the islands has meant that only a handful of other tree species ever arrived. So it is that in the unending battle between rock and life in Hawai'i, the Ohi'a tree is often the main combatant.

The Ohi'a trees aren't entirely alone as colonizers of barren landscapes in Hawai'i. The ʻŌhelo ʻai (Vaccinium reticulatum) is a shrub that can be found on new cinder cones, ash fields, lava flows and alpine slopes. The berry is edible, and is a treat for the nēnē, the native Hawaiian Goose. The geese in fact have a lot to do with spreading the seeds in the inhospitable environments of volcanic landscapes (they leave the seeds in their droppings). I'm trying to think of any other plant or shrub that produces mature fruit when it is only an inch or two high (as in the picture below).

ʻŌhelo ʻai (Vaccinium reticulatum)

There are a number of native fern species as well, growing in the most inhospitable environments I can imagine. Those below are growing in a pit on the flank of Mauna Ulu, which came into existence during a series of eruptions from 1969 to 1974.

And then there were the "furry rocks" I saw on Saddle Road at the pass between Mauna Loa and Mauna Kea. The mosses and lichens survive on the surface of the rock itself, and draw out nutrients directly from the minerals. The acids produced by the plants contribute to the alteration of the basalt to various clay minerals that end up producing pockets of soil that support numerous other plants. Forest succession eventually produces mature rainforests over time (at least with the cessation of constant lava flows as some of the volcanoes go dormant).

I guess "life finds a way" ended up as the predominate theme as I wrote. I was musing, though, about those high slopes of Mauna Loa at 11,000 feet where I saw no visible life. All the normal ways that rock is destroyed don't seem to apply up there. There are no plants to aid in the production of soil. There are no rivers to carry away sediment (any water seeps into the cracks and fractures of the lava flows and emerges far downslope). There are no glaciers. Snow falls on both Mauna Loa and Mauna Kea, and there were glaciers thousands of years ago, but they have little influence in the present day (one of the talks at the conference I attended concerned the permafrost at the summit of Mauna Kea). Waves can't attack the rocks until the islands have subsided enough, a process taking millions of years. Mass wasting has little effect on the gentle slopes of the giant shields, although gigantic megaslides eventually destroy the flanks of the volcanoes and ultimately lead to their destruction. The barren lava fields on the high flanks of Mauna Loa seem permanent until one realizes that they will no doubt be covered by new lava flows in a matter of decades or centuries. And when the volcano goes dormant or extinct, time (and life) will indeed destroy the rocks.

Life creeps ever higher towards the barren summit of Mauna Kea

Dispatches from the Road: Kipukapuaulu, a Residence of Godly Existences

As noted previously, I'm actually not on the road anymore in Hawaii, but since I had the idea for this post while I was there, I'm still calling it a dispatch. And actually, the first two pictures are aren't from my recent trip either, but they illustrate very nicely the idea of a kipuka. The picture above shows a number of cinder cones in the high summit valley of Haleakala on the island of Maui. If you look closely at the rough, blocky a'a flow below the closest cone, you can see an odd smooth area that I have enlarged below. The lava flowed around the small area of older rock, and that is what a kipuka is: an area of land that is completely surrounded by a lava flow.

If the land surface pictured above had not been at 8,000 or 9,000 feet, one could imagine that a forest growing within the kipuka might have survived the volcanic eruption and lava flow, and in the aftermath would be isolated from any surrounding forest tracts.

That's what happened at Hawaiian Volcanoes National Park on the Big Island of Hawai'i. About 600 years ago, a lava flow from Mauna Loa overwhelmed the forest of mature Koa and Ohi'a trees, but left a fragment of the woodland sitting on lavas 8,600 years old unscathed. The kipuka was often mantled with ash from the eruptions of nearby Kilauea, but the forest persisted. Today, the kipuka contains one of the most diverse collections of native flora on the Big Island. A beautiful and serene one-mile trail winds through the unique preserve. The place is called Kipukapuaulu, or the Bird Kipuka. A Hawaiian elder calls it a "Residence of Godly Existences".

It wouldn't be quite correct to describe Kipukapuaulu as an untouched pristine environment. At one time it was, but cattle were released on the islands in the late 1700's, and pigs and goats moved in as well. The natural flora of the kipuka had no defenses against the aggressive grazers, and by the early 1900's, the kipuka was a park-like grassland shaded by the "grandfather trees", the older Koa and Ohi'a trees that the cattle couldn't reach. A park sounds pleasant enough, but the trees couldn't reproduce (the saplings were quickly eaten), and the diverse understory of shrubs and perennials had been replaced by alien grasses.

The potential value of the kipuka as a possible preserve of rare native species was recognized surprisingly early by botanists, who arranged for the removal of cattle in 1928, and the removal of goats and pigs in 1968 (a fence surrounds the kipuka). Volunteers have removed some of the worst of the invasive weeds and grasses, and seeds lying dormant in the soils started sprouting. In other cases, native species were planted. After a few decades, the kipuka is returning to a condition that is comparable to its natural state.

One of the strangest stories I've run across regarding Kipukapuaulu is that of the small tree called hau kuahiwi (Hibiscadelphus giffardianus). A botanist named Joseph Rock (shouldn't he have been a geologist?) discovered the sole remaining specimen of the plant on planet Earth in Kipukapuaulu in 1911 (the cows had not quite finished it off). He managed to collect enough seeds to get a few sprouts going, and so the plant survives in captivity, so to speak. A couple have been planted in the kipuka that was its ancestral home.

The kipuka came under protection sort of in the nick of time. Some of the "grandfather trees" that shade the preserve have been dying off in recent years (like the Ohi'a tree in the picture above). Ohi'a trees (Metrosideros polymorpha) are one of the most extraordinary of the native trees in Hawai'i. The thrive in a greater range of environments than pretty much any tree on the planet, being found in places as diverse as new lava flows, desert slopes, and alpine ridges. They can appear as small shrubs or as huge rainforest canopy trees a hundred feet tall. The trees in the kipuka may be dying of old age, or because of a series of droughts in recent years, but new Ohi'a trees will be able to grow to replace them now.

A few steps off the trail is an intriguing opening in the ground. It is a lava tube, part of the plumbing system of basaltic lava flows. Because it has existed for more than 8,000 years, it is one of relatively few that has some species of cave-dwelling organisms (including the first one discovered in Hawaii). Like the rest of the kipuka, the cave was heavily impacted (in this case by graffiti artists, vandalism and trash), but visitors are now encouraged to leave the cave alone.

The preponderance of native plant species attracts the native bird species to the kipuka, and they can commonly be seen flitting about in the forest canopy. They are frustratingly difficult to photograph, mind you, and I am actually cheating here by showing a picture of an Apanane from a 2004 visit.

The bird below is often seen in Kipukapuaulu, but it is not actually a native. It is a Kalij Pheasant, a 1962 import from southern Asia. There is some concern about the effects they might be having on the vegetation. You can gauge the level of interest by biologists by the fact that this one had a leg tag. There is a hen hidden in the leaves to the right.

Kipukapuaulu is a fascinating and peaceful place to visit. The nature trail is well-marked, and much of my information in this post is drawn from the Kipukapuaulu Trail Guide, written by Tim Tunison and Andrea Kaawaloa-Okita, and published by the Hawai'i Natural History Association. Additional information was gleaned from the book Hawai'is Native Plants by Dr. Bruce Bohm.