|A section of the old Chain of Craters Road buried by lavas in the 1969-74 Mauna Ulu eruptions.|
Sunday, June 26, 2016
|The Pu'u O'o cone from above Hilo|
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.|
|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.|
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|
|A rootless shield on the Pu'u O'o lava flow.|
|Active lava flows on the slopes below Pu'u O'o. This would have been a real spectacle at night.|
|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.
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
|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 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.|
|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 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.
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 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 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|
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.
Coming up: explorations in a rapidly changing national park!