Open Eye: It's up, down and sideways
OUGS members trekked above the clouds to pay homage to Pele on a Hawaii field trip, reports Linda McArdell
Tuesday 03 August 1999
Volcanic places like Hawaii are where land is created - an awe inspiring phenomena that has been happening for thousands of millions of years. Were it not for volcanoes, we would probably all be fish - now there's a thought!
We started our excursion on Oahu, amid the skyscrapers of Honolulu. After a morning's relaxation, to recover from a 20-hour journey we plunged right into the geology (well, some relaxed, and six of us went kayaking to an offshore island to look at dykes). You have to remember, said Peter Francis, that the volcano is moving up, down and sideways all at the same time, and we set out to see how.
We studied UP mainly on Kilauea. At 4078ft it is the smallest and youngest of the Hawaiian volcanoes above sea level. It has been erupting almost continuously for most of this century and many times in recorded history, although it was born on the sea floor thousands of years ago.
We had actually started to study `up' on Mauna Kea. It is classed as a late stage shield volcano, so has probably stopped going up. At 13,796ft, the trip to the summit meant a day's outing in specially hired 4WD vehicles. On the way up, crisp packets exploded; on the way down, water bottles caved in and crumpled.
Exhilarating though it was to be up there above the clouds and surrounded by more astronomical telescopes than you are ever likely to see in one place, the thinness of the air made exertion difficult. Nevertheless, we parked the vehicles and hiked to the snow-capped summit. From there we enjoyed a totally surreal vista of small rusty red volcanic cones dusted with snow, looking very much like a comic cartoon depiction of Mars.
We took lots of photos, threw snowballs and paid homage to Pele, (the Goddess of the Volcanoes) before returning to the vehicles, lunch and the trip back to sea level.
Our base for the duration of our stay on Kilauea was the Military Camp, a US forces recreational facility, where we slept in small cabins scattered among lawns and trees. Here, we literally paddled between cabins, mess, bar and store while torrential rain turned roads into rivers.
Undeterred, we explored lava flows, recent cones, craters and lava tubes by day and toasted ourselves (sodden boots and clothes) by log fires at night. Apparently, 11 inches of rain in three days is unusual.
The day we left for the drier climes of Kona it was clear and sunny, and Mauna Loa (13,679ft).was capped with fresh snow: beautiful. At the summit of Kilauea sits the crater of Halemaumau. This was a lake of molten lava until 1924, when it suddenly drained, water entered the part-empty magma chamber, and a huge explosive eruption occurred. We inspected the ancient rocks thrown up by the force. Today, it is just a solid crater that steams gently as rainwater seeps through cracks to hot rock below the surface.
Many distinguished travellers and scientists visited it around the turn of the century, including Mark Twain, and Dr Thomas Jagger, who later founded the Hawaiian Volcano Observatory (HVO). The flows were as light and frothy as meringue, with a wafer thin crisp crust that shattered like light bulbs when walked on.
The remnants of the 1982 fire fountain could be found as `Pele's tears' - small teardrop-shaped glass-like beads of lava. We climbed Mauna Ulu which last erupted in 1974 and saw lava tree moulds, and `Pele's Hair' - spun glass formed when erupting spatter is caught by a strong wind.
From the black sand beach of Kalapana we saw Pu'u O'o, the currently active cone, perched on the top of a scarp in the middle distance (the village of Kalapana was obliterated by lava between 1986 and 1991). One night we watched the glow of red hot lava as windows formed in the hardened crust of the 11km flow as it swept down the scarp towards the sea. The orange glow on the underside of the steam plume as the lava hit the water was breathtaking. Molten lava is about 1200C and soon hardens on the surface, but with continuous feed from deep within the volcano, it continues to flow inside the hardened crust.
This was what we had come to see... the building process. It takes a long time. There is a new volcano growing beside Kilauea, called Loihi, it is still about 1.5km beneath the sea, and will take about another 50,000 years to emerge.
The day we left Kilauea, we hiked a strenuous 5.5km along the coastal edge of the Pu'u O'o lava fields (and back!) to watch its molten lava spewing into the sea amid the now familiar billowing clouds of steam. Here, there were the most diverse shapes and colours of lava imaginable - so fresh, the surfaces were like burnished metal, some silver, some gold and some pewter. And the shapes - some like thick tree roots, others like the finest twisted twine or coiled ship's rope - then a most unusual sheet-like form - crumpled black satin, somebody said. And there we were, standing on the newest land on earth. A strangely humbling experience.
We had our first view of a Pali at Nuuanu on Oahu, famous because King Kamehameha I, on invading in 1795, chased defenders up the Pali, from which many jumped to their death, which gives an idea of the meaning of Pali it's Hawaiian for steep cliff.
From Nuuanu, Pali is a fantastic view along the dramatic, near vertical scarp of the Koolau Shield volcano or what is left of its seaward side. About half its width has now fallen into the sea, and about 1.5km of its height has eroded away. The leeward side is incised with deep valleys, evidence of the high rainfalls attracted by lofty land masses in mid ocean catching the trade winds. Consequently it is very green with lush foliage, and frequently swathed in cloud.
At its prime, Koolau would have been similar in size and shape to Mauna Kea on Hawaii. We were to see many examples of Pali all over Oahu and Hawaii, as scarp formation happens on young and old volcanoes alike.
The reasons are not too surprising, as Christina Heliker from the HVO had told us, "Ocean island volcanoes are inherently unstable structures built as they are from piles of rubble on top of slippery sea floor sediments in the middle of the ocean. Add to that regular earthquakes caused by rising magma, explosive eruptions when water seeps into the magma chambers, and the flexing of the earths crust as it is either loaded (growing volcano) or unloaded (eroding volcano). The only surprising thing is that they grow to be the size of Mauna Kea in the first place."
We had spent a morning at the HVO as their guests, and had talks from some of the geologists who are actively monitoring Kilauea, before seeing the seismographs and computers where results were coming in continuously.
The thought of volcanoes moving sideways is rather mind boggling, especially when you have just been told that the one you are standing on had moved sideways by 3-5km, when in its heyday.
This was at the base of the Koolau Shield on Oahu, where we were about to go down into Kappa quarry to look at the most spectacular collection of dykes I have seen outside of The Oman. These are now exposed by the quarrying process but were formed about 2km below the original summit. They were part of the growth process of the volcano itself, each dyke representing an injection of molten rock from deep below the earths crust, that would usually arrive at the surface and eventually form a lava flow.
There were more dykes here than original rock, by a ratio of 2:1. Pressure from growing dykes causes earthquakes, and rifts on the surface as they push the volcano sideways.
On Kilauea we had seen the SW Rift, formed by a great earthquake in 1868; it is several metres wide and several deep near the Caldera, but becomes a yawning fracture further away. However, it was already filling with lava from more recent summit eruptions illustrating why the sideways movement is not very evident on the surface, and therefore difficult to appreciate - except we had seen the quarry at Kappa several days before.
So, it seems that in order to go UP, the volcano must also move SIDEWAYS, which in turn causes earthquakes, fractures and rifts which help it to fall DOWN. Nice one Peter!
For more information about OUGS contact the national secretary, Joe Jennings, on 01902 735118.
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