Dr Trevor and Chris Watts (UK)
This is the last of five articles on the ‘Chain of Craters Road’ on Hawaii’ Big Island. The articles are in the form of a road trip that you can follow if you are lucky enough to go to this wonderful part of the world to see its volcanic scenery. Being a road trip in the USA, distances along the road and by foot are given in yards and miles, while measurements are provided in more European and scientific metric units.
|A word about Hawaiian pronunciation – Hawaiians do not say ‘Morna Ulu’ for the Mauna Ulu volcano. They split most vowels up separately: thus, ‘Mah ooner Oo loo’. Similarly, ‘Kill ow eh uh’, for Kilauea; and, ‘Halley mah oomer oo’, not ‘Halley mow mow’, for Halema‘uma‘u; and, ‘Poo ooh Poo ah I’, for Pu’u Pua’i.|
3.7 miles: the pahoehoe flow
Adjacent to the road, this is a wide-spreading series of flows dating mainly from 1969 to 1974, from Mauna Ulu. In the southern part, the lavas also originate from the smaller volcano of Mauna Loa o Mauna Ulu. These are varied, but mainly formed as thin, smooth sheets. They were often broken up after solidifying by being pushed upwards into low mounds by fresh lava invading beneath them and also by the lava beneath them draining away, causing the thin skin to collapse.
The forest that existed here is now seen as tree moulds. These are generally in an excellent, fresh condition, and some are very tall (Fig. 1).
One, right next to the road, demonstrates how the lava wrapped around the base of three small trees in a clump, which eventually toppled over (Fig. 2).
In other places, the thin lava was slowed in its movement and began to wrinkle up, forming small rivers of pahoehoe lava. Nēnē geese – the Hawaiian State bird – are frequently found here (Fig. 3).
5.6 miles: Kipuka Kahali
A ‘Kipuka’ is a small area of original woodland that has been surrounded and isolated by relatively recent lava flows (Figs. 4 and 5).
They are survivors and are described as ‘ancient’, as much as any part of Hawaii is ‘ancient’: after all, the whole island has been created and repeatedly buried in flows of lava and/or ash deposits.
Kipuka are often called ‘Treasure Islands’ because they are havens for rare native birds and insects as well as the vegetation. We’ve stopped close to this one several times, but going into it isn’t encouraged – and there are others elsewhere.
6.4: miles: Mauna Loa o Mauna Ulu
This volcanic peak (Fig. 6) erupted lava that covered 4,400 hectares, to an average depth of six metres between 1969 and 1974, crossing and closing the Chain of Craters Road several times.
Much of the lava is characterised by its smooth surface, in gentle mounds and lobes (Fig. 7). Particularly in wet weather, the surface is highly reflective because of its skin of silvery silica.
7.0 miles: Kealakomo Lookout – and Pele’s hair
This timber structure (Fig. 8) is located on the edge of the inland cliff called the Hōlei Pali. The cliff itself is the scarp face of a fault that dropped on the coastal side relative to the Eastern Rift Zone. The main downward rupture of the fault in historical times was in 1868, and again in 1975, when there was a magnitude 7.2 earthquake.
This is a great place to rest up and picnic. The views down the flows to the coast, and over the ocean, are superb on days when the haze lifts and when the vog doesn’t drift this way. Downslope, the lava has flowed over the cliff in an unbelievable variety of forms – a photographer’s joy – often alternating between very rough a’a lava and a mix of silky smooth lobate and pahoehoe lava (Figs. 9 to 11).
For the enthusiast, these vast flows are well worth exploring – they are rich in all kinds of lava formations, an ancient site of petroglyphs created sometime between 10,000 and 600 years ago (depending on whose evidence/opinion you believe), and a superabundance of Pele’s hair in the folds of the lava. These very elongated, golden, non-crystalline strands of silica are particularly common in this area (Fig. 12).
Explanations of Pele’s hair almost invariably give their origin as being highly fluid lava droplets that were expelled during explosive eruptions. The speed of the ascent, or high winds, drew the droplets out into long thin threads. Until it closed, the Jagger Museum agreed with this explanation, and displayed a sample that was curled and looked somewhat like real (if straggly and tangled) hair. Hawaii Volcanoes Observatory (USGS) staff also credit its formation with bubbles of lava that burst open when they reached the surface of bubbling lava, “The skin of the bursting bubbles flies out, and some of the skin becomes stretched into these very long threads… These strands of lava-turned-glass usually have a small sphere at the end, but this usually gets broken off…” (Don Swanson).
However, the USGS also illustrates several of its publications with pictures of a rather different type of Pele’s hair. They are shorter (generally less than 15cm to 20cm long), golden silica needles. Most are straight. Fine threads and needles of this kind are found en masse in thousands of crevices across these lava fields. If you Google ‘Pele’s hair images’, you will find innumerable pictures of huge masses of these golden hairs.
We struggle to believe that all the Pele’s hair found hereabouts originated in distant highly explosive eruptions during high winds. To us, what seems more plausible is that they have weathered out of the rounded surface of lobes and rolls of lava. Uncountable thousands of lobes and rolls of lava in this area display a striped surface on which golden silica strands have separated from the blue/black pyroxene and plagioclase matrix. We have watched them form as the molten surface begins to cool and the constituent minerals begin to separate out (Fig. 13). As the surface continues to expand under the internal pressure of new lava intruding, the separating minerals are slowly (in the course of a few minutes) stretched out in long threads. They set solid within a few more minutes.
In the following years, as the surface begins to weather away, the background minerals disintegrate at a microscopic level, but the tougher silica strands remain intact. There are many thousands of examples here of finely-striped lava lobes with partly-separated golden strands ‘working their way free’. It’s possible to grip a loose end and carefully tease one free of the rock (Fig. 14) – it almost ‘twangs’ free, as the silica needle has a molecular preference to be straight, but the lava surface is curved. Normally, they drop into the nearest crevice or may blow away in the wind. Either way, they end up as handfuls of fine, brittle, golden ‘hair’. And this is the place to find them.
One other formation found here is noteworthy. After Pele’s tears (which are small pieces of solidified lava drops that definitely formed when airborne particles of molten material fused into tear-like drops of volcanic glass) and Pele’s hair, there now comes Pele’s froth – or foam. This is an extremely lightweight and delicate mass of tiny ‘bubbles’ that are one or two millimetres in diameter (Fig. 15).
Found in the same crevices as the hair, the foam masses we have seen have been from about 2cm to 10cm across. Known technically as ‘reticulite’, it is lava froth that forms in the boiling fire pit craters, such as Halema‘uma‘u and Puʻu ʻŌʻō, when the lava is very gaseous. It then needs an explosive burst to send it high into the air, where, weighing almost nothing, it may be carried for many miles.
Interestingly, although technically it is the extreme form of pumice, it does not float. This is because the bubbles coalesced whilst still molten, the skin of the bubble surface popped, and only the reticulated ‘frame’ or latticework of the froth was left. So they aren’t actually bubbles any longer – water soaks through them almost immediately and they sink.
And the ‘End of the Road’
Finally, of course, the sight of the ‘End of the Road’ is not to be forgotten (Fig. 16).
It’s an impressive sight to see a road come to such an end – that a flow of lava can totally bury a road, so abruptly in time, from one minute to the next during the eruptive period of 1983 to 1986. And so suddenly in space, from one step to the next. It’s nature – known as Pele in these islands – being casual with our best efforts.
|Almost all the photographs were taken by one of us – Trevor or Chris – except the few that are credited separately. These are available as Public Domain Images from the United States Geological Service (USGS), particularly the Hawaiian Volcanoes Observatory. Innumerable Internet sites provided background information, such as dimensions of craters. The USGS is invariably helpful in answering specific queries and providing access to wider sources. Their weekly publication, ‘Volcano Watch’, is invaluable for general information as well as updates on theories, eruption activity, and trail and road closures and re-openings. Fig. 4 is an unaltered photo by Thomas Tunsch (www.panoramio.com/photo/80484783).|
About the authors
Trevor and Chris are keen amateur geologists living near Nottingham, England. They have climbed many volcanoes throughout the world. Sharing the exploration, photography and writing, they have had numerous articles published on the subjects of volcanoes and their other geological interest – dinosaur footprints (including in this magazine). Now retired from her work as a teacher and head teacher, Chris paints in watercolours, silks and pastels, mostly animal portraits and flowers. Trevor, formerly a teacher, headteacher and school inspector, now writes short stories and poetry for competitions, publication and the mental challenge.