Sunday, June 26, 2016

The Hawai'i That Was: Living on Uncertain Ground - The First Human Wave Arrives

The southeast coast of the Big Island of Hawai'i is a barren blasted land. One can blame it on the lack of rain, but though it is arid, rainfall is plentiful enough to support forests nearby. One only needs to look up the Holei Pali to know right away what the problem is: it's ground zero for the basalt flows emanating from the Kilauea shield complex. These slopes have been covered repeatedly by eruptions, most recently from 1969-75, and during the ongoing eruption that began in 1983. As we will see, each eruption is a paradox of creation and destruction.
The pali, or cliff, belies the description of a shield volcano with gentle slopes. It turns out that the southeast slope of Kilauea is sliding slowly into the sea, and the cliffs are actually giant fault scarps. To most people, "faults" means earthquakes, and there have been some powerful events in this area, including a 7.9 magnitude quake in 1868, and a 7.2 magnitude tremor in 1975 that killed two people.
We were headed down Chain of Craters Road in Hawai'i Volcanoes National Park on the second day of our recent journey. The class, a hybrid course covering geology and anthropology, was having a first look at some of the archaeological sites on the Big Island, and as we looked around, it was hard to imagine living in this strange and ever-changing landscape. There is no development along the road, and yet, if you come across old maps, you will find a string of place names along the route: Kalapana Garden, Waha'ua Heiau, Royal Gardens, the Queen's Bath, the Black Sand Beach of Kaimu, and a national park visitor center. They are all gone now, buried in basalt lava flows. It's a tough land.
A section of the old Chain of Craters Road buried by lavas in the 1969-74 Mauna Ulu eruptions.
And yet, people have lived here, and for hundreds of years. Despite the lack of water and soil, despite a lack of coastal access, there are hundreds of archaeological sites that have not yet been buried beneath the advancing lava flows. The original Hawaiians were Polynesian voyagers, probably from the Marquesas Islands, 2,500 miles to the south (although legends speak of an earlier race of people, the Menehune). The timing of their arrival is debated, with estimates ranging from 1,700 to 800 years ago. Aside from rich fishing along the shorelines, there was little food for the colonizers, but they brought their own plants and animals to assure their survival: taro, breadfruit, banana, coconut, as well as pigs (pua'a) and chickens (moa), and unfortunately, rats. We checked out a small village site that was partially buried in the 1969-74 eruptions (below), and then headed to the Pu'u Loa Petroglyph Trail.
The arrival of humans on the islands heralded huge changes for the native plants and animals. For millions of years, the flora and fauna had evolved in isolation, and had few defenses to the effects of the grazing of pigs and the predation of rats. The first wave of human colonization resulted in extinctions or vast declines in the populations of native plants and animals, especially the birds.
What we know of the culture of the first Hawaiians comes from oral traditions, historical writings since European contact, and archaeological investigations of the older sites. More information comes from linguistic analysis of the Hawaiian dialect. To me, the amateur, the most fascinating hints of the past come from the intersection of humans with the rock: petroglyph art. The barren coastal plain at Pu'u Loa has the largest collection of petroglyphs on the island, with at least 23,000 individual carvings.
A relatively level trail crosses 0.75 miles of the basalt flows to the petroglyph site, where a boardwalk protects many of the carvings. Our ranger guide led us farther up the slopes to another field as well. The rock carvings carry a tremendous amount of religious and cultural significance, especially in a society that did not have written records (although oral histories are extensive). 
I try to imagine what a revelation the Big Island was to the first Hawaiians. The Polynesians may or may not have had a cultural memory of volcanism, but the Marquesas Islands were not one of the active chains where they would have seen volcanoes in action. What did they think of these blasted plains of lava in a place where plants should have been growing? What did they think as they witnessed their first eruptions, and perhaps the destruction of some of their villages? It must have been a profound and terrifying experience.
We reached the end of Chain of Craters Road and had a look at the Holei Sea Arch and the rugged coastline. This was not the stereotypical white sandy beach with surfers and high-rise hotels. It was a violent battleground between ocean waves and volcanic rock. The lava flows destroy human developments, but they also create new lands, providing a balance to the constant destruction brought about by by the raging sea.

The Hawai'i That Was: Pu'u O'o, the Volcano We Couldn't See

The Pu'u O'o cone from above Hilo
Disclaimer: This is NOT happening right now! These pictures are from 2009.

Pu'u O'o is the invisible volcano on the Big Island. It's been the center of eruptive activity for much of the last thirty years, but there are very few easily accessible localities from which it can be seen. One pretty much has to fly over it to see anything at all.

We are continuing a journey to understand the Hawai'i That Was, seeking to understand the islands as they were before European contact, and before Polynesians arrived a thousand years earlier. Understanding the islands requires an understanding of volcanism. The islands exist only because of lava, and in observing active eruptions we see the origins of each of the Hawaiian islands.
Getting closer to the Pu'u O'o cone. Notice the lack of surface flows of lava. It's almost all beneath the surface in lava tubes.
There is a huge unknown involved with every journey to the islands. The volcanoes refuse to follow a schedule, and feel no need to be convenient to the itineraries of visitors. It's true that Kilauea has been erupting continuously now for more than thirty years, so there is a fair chance that the eruption will continue for the foreseeable future. Then again, the eruption could end tomorrow. There's just no way to know. So, one plans for the possibility, but leaves a lot of alternate activities if lavas aren't visible anywhere.
The location of the lava tube system was obvious. Every so often the roof of the tube would collapse, forming a skylight that emitted steam and other gases.
Kilauea is the sole volcano erupting on the island right now, although Mauna Loa is showing a few hints of possible activity. The lavas are exposed at two localities, at Halemaumau in the Kilauea Caldera (see the previous post), and at the cone of Pu'u O'o on the east rift zone about ten miles away. During the many months that we were planning the trip, Pu'u O'o was pretty much just simmering with no active lava flows since 2014, when the town of Pahoa in the Puna District was briefly threatened (damage was thankfully limited).
So we had a hard decision to make: do we bust the budget on a helicopter flight in hopes of seeing lava flows, though there have been none for more than a year, or do we make other arrangements? We opted to make other choices, which was good because we arrived on the islands during a wet spell, and we probably would have seen little through the rain clouds, although a small lava flow started a week before we arrived. It's now three miles long and approaching the coastal pali (look here for a recent video), but we've been home for nearly two weeks. We just plain missed it.
Looking into the crater of Pu'u O'o, source of the lava flows
The situation was different in 2009, the last time we held a class on the islands. Pu'u O'o had been very active for more than a year, with a broad "delta" and lava tube system feeding basalt into the ocean. We opted for the helicopter flight and were richly rewarded. For one reason or another, I've never collected these pictures together in a blog post.
A rootless shield on the Pu'u O'o lava flow.
The first two photos above show the Pu'u O'o cone and crater from a distance. At various times it has been a more prominent cone, but at other times it collapses. Lava left the cone through a series of lava tubes and flowed southeast towards the coast. Sometimes lava would well up through a skylight, forming a small "rootless shield" like the one in the picture above.
I was surprised, almost disappointed by the lack of "rivers" of lava, but our pilot found a recent breakout, and we saw glowing lava and silvery pahoehoe flows that had formed only hours earlier.
Active lava flows on the slopes below Pu'u O'o. This would have been a real spectacle at night.
The silvery reflective appearance was caused by the formation of a thin film of volcanic glass on surface of the flow. The glass breaks off and degrades quickly, leaving behind the more characteristic dull black or dark gray surface.
A skylight over a lava tube.

If you are having trouble visualizing the scale, realize that we never dropped below 500 feet in altitude. The skylight above is probably 30-40 feet across.
Minutes-old breakouts
Our flight continued over the pali (cliff) and onto the coastal plain. Farther from the vent there were more kipukas, islands of forest that were spared from destruction as the lava flowed by. Kipukas are the seed repositories that would eventually cover these flows with new forests.
And then we reached the coast, where the lava emerged from the lava tubes and plunged into the sea. The union of hot lava and cold seawater was explosive. The lava shattered into black sand on contact.
Occasionally we could see lava through breaks in the clouds of steam.
We flew around, but not through the steam cloud. It is a noxious mix of hydrogen sulfide and acids.
As I went through the pictures much later, I found that one of them gave an end-on view of the entire eruption from Pu'u O'o on the right to the ocean entry on the left (below). The distance between is seven miles (11 kms). It's hard to describe the feeling of seeing the forces of creation and destruction at war with each other. We were seeing the continuing birth of the Big Island. Eventually the fires here will die, but a new island will emerge off to the south (it's already got a name: Lo'ihi. Look for it to appear in a few thousand years).
It's not entirely true to say that we never saw Pu'u O'o on the trip a few weeks ago. There is a spot on Highway 11 near Glenwood Road and the Hirano Store where the cone can be seen. During our reconnaissance before the students arrived, we stopped and had a brief look (below). Of course, once the students were with us we tried again, but it was hidden in the rain.
The Pu'u O'o as of this writing has advanced three miles down the upper slopes of the east rift zone and is approaching the coastal pali. If the eruption keeps up, the flow may once again reach the sea, and once again cover the extension of Chain of Craters Road. After the close call of 2014, the road was rebuilt as an emergency escape route for people in the Puna District. Such are the risks of living on an active volcano.

In the next post, we'll see evidence of a conflict between the gods and humans as they settled the island, a conflict that continues today.

Friday, June 24, 2016

The Hawai'i That Was: Walking a Lake of Fire in "the Little Source of Great Spewing"

Kilauea Iki eruption in 1959. The prevailing winds caused debris to pile up behind the fountain, forming the Pu'u Pau'i cinder cone. Source: US Geological Survey
Kilauea is one of the five major shield volcanoes making up the Big Island of Hawai'i. As we found in the last post in this series on the "Hawai'i That Was", Kilauea is the most active of the island's volcanic centers, with an ongoing eruption dating back to 1983. On our first full day on the island, we had a look at the smoking pit of Halemaumau, but in the afternoon, we headed over to Kilauea Iki ("little source of great spewing").
Kilauea Iki from the northeast rim. Pu'u Pua'i is the mound on the right. The steam and gas in the distance is the ongoing eruption of Halemaumau. This picture is from 2009; it was foggy at this point on our recent trip.
Prior to the 15th century, Kilauea Iki was not a crater at all, but was instead a small shield volcano called 'Aila'au. It collapsed in the aftermath of an eruption, forming a pit crater 800 feet deep (the present crater is only half that depth). One of the lava tubes formed in the eruption is today known as Nahuku (Thurston Lava Tube). It is lit, and is an easy walk from Crater Rim Road (good luck finding a parking spot on busy days). Our goal for the day was to hike the north rim of the crater, descend into west end of the crater itself, and then climb the east rim, a distance of about 3 1/2 miles.
If that looks like an abrupt dropoff to the left, it is; it's a sheer 400 foot cliff into the crater.

The trail begins in a phenomenal high altitude rain forest (4,000 feet, ~100"/year) composed mostly of native Ohi'a trees and ferns. On my last trip in 2009, the forest was filled with kahili ginger, an aggressive invasive species. It has pretty flowers, but forms thickets that crowd out the natives. I didn't see any at all this time, although I am sure they are lurking in the forest away from the trail (kudos to the trail crews removing them).

Another serious pair of problems in the native rainforests were the feral pigs and goats. The pigs arrived with the Polynesians over 1,000 years ago. The goats arrived with Captain Cook and his crew, the first Europeans to discover the islands in 1778. Both animals wreaked havoc on the forest. The animals were finally removed by the 1990s, so the forests at Hawai'i Volcanoes are approaching something resembling their original state.
Our first look at the Pu'u Pua'i and the crater interior

The day had been overcast, but as we passed in opening in the forest we could see across the crater to Pu'u Pua'i, a mountain that is younger than I am. The extraordinary eruption that produced this landscape began in November of 1959 as lava started pouring from a rift system on the south side of the Kilauea Iki crater. The eruptions consolidated into a single vent within a few days, and for the next five weeks, spectacular things happened.

Seventeen different times, lava shot high into the air, and the crater filled with millions of cubic yards of simmering basalt. At the end of an eruptive episode, some of the basalt would drain back into the vent, but as the weeks passed by, Kilauea Iki crater filled to a depth of 400 feet (recall the original crater was 800 feet deep). During the latest stages of the eruption, the lava fountain reached a height of 1,900 feet (580 meters), the highest ever recorded in Hawai'i.

In the aftermath of the eruption there was a brand new cinder cone, and a lake of molten lava. During the final draining event, the lake level dropped about fifty feet leaving behind a "bathtub ring" (sciency version: "lava subsidence terrace"). We descended out of the forest, over the bouldery terrace, and into a ghostly barren landscape. After a few minutes we passed the remains of the eruptive vent at the base of Pu'u Pau'i (below).
The eruptive vent of Pu'u Pau'i

From then on, we were walking on a lake of fire. The eruption may have ended in 1959, but a four hundred foot deep lake does not cool all at once. It doesn't take weeks, or even months. It takes decades. Four months after the eruption, the crust was only 9 feet thick! Drilling allowed researchers to track the cooling process. In 1967, the crust was 90 feet thick, and in 1975 it was up to 180 feet (See Hazlett's book for details). The lava lake was more or less solid by the late 1990s, but there is no doubt that it is still very hot down below. Whenever the rain starts (roughly every five minutes, it sometimes seems), steam can be seen rising from fractures in the lake surface (below). Steam rising up the old drill holes is hot enough to scald.

We continued across the surprisingly flat surface of the lava lake. There were pressure ridges and fractures here and there, but the trail was easy to follow, using ahu (cairns, or rock piles).

One of the most astounding things about this lake of fire is the stubbornness with which life seeks to take root. Native Ohi'as are one of the most adaptable trees on the planet. They can form hundred foot high canopies in the native rainforests, but they can also grow in one of the most ghastly environments possible, that of a fresh lava flow. We passed dozens of scraggly bush sized Ohi'as and hundreds of small ferns. Recall that the forest on the rim above is no older than 500 years. In a few centuries (barring new eruptions, which are likely), this barren surface will be a thick forest.

We reached the eastern edge of the crater just as the rain began to pour. The change back to rainforest was abrupt. We climbed four hundred feet up a relatively gentle gradient and found our way to the vehicles. We had crossed the lake of fire and survived!

We never really saw the sun on the day's journey, but when we visited in 2009, we were treated to a gorgeous rainbow as we set off across the crater floor. It was astounding.

If you ever have the chance to visit Hawai'i Volcanoes National Park and want to see a bit of the native environment of the islands (the Hawai'i that was...), this trail is one of your best chances to see what it was like.

Read more:
The Kilauea Iki Trail Guide from the National Park Service
Explore the Geology of Kilauea Volcano by Richard Hazlett (Hawai'i Pacific Parks Association)

Wednesday, June 22, 2016

The Hawai'i That Was: The Abode of the Gods and Creation at Kilauea

The ongoing eruptive activity at the summit caldera of Kilauea on the Big Island of Hawai'i.

You aren’t hearing this from me (well, okay, you are), but sometimes teaching is just a little bit like carnival barking. You have to be entertaining about something that actually isn’t all that unusual or interesting. And sometimes you have to reveal just a little at a time to keep the interest going until the dramatic finish (“the butler did it!”). During our recent exploration of the Hawaiian Islands, I chucked all that. We started our trip in Hilo on the Big Island, we were only thirty miles from Hawai’i Volcanoes National Park, the volcano was erupting, so our first morning as a group we headed up the highway to see an erupting volcano. It was a first for everyone on the trip.
When was the last time you saw a class paying complete attention to the subject?

There's a secret to keeping the attention of a class of students. It's easy really...just put them in front of an erupting volcano! What we could see was astounding: a lava pit that has been erupting continuously since 2008, on a volcanic shield that has been erupting continuously since 1983! The shield volcano is called Kilauea, and the crater within the summit caldera is called Halemaʻumaʻu. The crater is said to be the current home of Pele, the volcano goddess of Hawai'i.

The current volcanism of Hawai'i is occurring only on the Big Island, and only on two of the five volcanoes that make up the island: Mauna Loa, and Kilauea. Mauna Loa is clearly visible on a physiographic map of the island (above), while Kilauea is less so (refer to the map below to see where it  is). Mauna Loa is gigantic, covering half of the island, reaching an elevation of  13,679 feet (4,169 m) with a volume measured at more than 10,000 cubic miles. From her base on the sea floor, Mauna Loa is the highest mountain on the planet at 31,000 feet. Kilauea is less massive, rising to only 4,091 feet (1,247 m). Mauna Loa and Kilauea produce roughly similar amounts of lava, but Mauna Loa tends to produce lots of volume in periodic eruptions (the last was in 1984), but Kilauea has become known for continuing eruptions that simmer along for years, with occasional outbreaks that flow down to the coast (or unfortunately through nearby villages).
Source: USGS

The eruptions don't come just from the summit calderas. Most of Kilauea's activity is actually elsewhere along rift zones, especially at a cone called Pu'u O'o (watch for a future blog discussion). There are two rift zones extending from each volcano, trending roughly northeast to southwest. It's tricky to determine the age of the volcanoes, since younger eruptions are constantly covering older eruptions, but Mauna Loa has probably been erupting for around 700,000 years (the oldest exposed flows are 200,000 years old), while Kilauea is perhaps 600,000 years old, with exposed rocks ranging from around 70,000 to 43,000 years ago.
Halemaʻumaʻu in 2002 before the present eruptive activity
This is a view that is no longer accessible for visitors to the park. In 2008, the lava pit in  Halemaʻumaʻu exploded and tossed foot-wide boulders at this overlook, and since then noxious and poisonous gases have made this spot dangerous. The frozen lava in the main crater dates to the 1920s when a molten lake of lava filled the crater floor. The gifts left at the crater rim show that many take the existence of the volcano goddess Pele quite seriously.

For this blog series on the "Hawai'i That Was", I'm intending to follow the itinerary we followed as a class, but I want to skip ahead a couple of days. In the daytime, the view of the lava pit in Halemaʻumaʻu was awe-inspiring, especially to those in our group who had never seen an active volcano (mainly all of them except Mrs. Geotripper and my fellow professor), but what happened three days later left me stunned.
Halemaʻumaʻu at twilight in 2009

When I was last on the island with students in 2009, a few of us waited for the sunset at Kilauea, long enough to see the glow of the lava lake in the twilight (it's overwhelmed by sunlight). It was neat, but not earth-shakingly spectacular, as can be seen above. At the time, the pit was maybe 200 feet across and 500-600 feet deep. We made arrangements to stay through the evening again, and I wasn't expecting much, but as we pulled up into the parking lot, I could see something was very different. The sky was glowing brightly long before we could see the crater (below).

The pit today is 500-600 feet across now, and in the weeks prior to our arrival on the islands the lava lake had been at a depth of 100-150 feet. But on the night we arrived, the lava had risen to within 88 feet of the floor of the crater, and the lava was splashing about over the rim. It was, as I said before, a stunning spectacle. We ran to the edge of the observation deck.
The lava lake was about a mile away. We couldn't hear anything, but what we saw was beautiful.
It was difficult in the dark to catch photographs of the fountaining lava, but the video did. I posted this a few weeks ago, but it's one of my favorite geology moments ever, so here it is again.

Coming up: explorations in a rapidly changing national park!