Dr Trevor and Chris Watts (UK)
This is the third of five articles on the ‘Chain of Craters Road’ on Hawaii’s 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.|
2.6 miles: the Hi’iaka lava field and lava tree forest
This is just across the road from the Hi’iaka Crater and is the later (May 1973) lava flow. It is very extensive and is little explored beyond the first 100 yards from the road. Before the eruption, there was a forest here, mainly of ʻŌhiʻa trees, but, on 5 May 1973, a series of fissures opened up and vast amounts of lava gushed forth (Fig. 1). Spreading over several miles, it devasted the forest, filled several former collapse craters, became ponded up at the Koa’e Fault cliff, and flowed away. It drained back almost to the original surface level. All within one day.
What it left behind is perhaps the most fascinating part of the whole area. Close to the road, the lava surface is very much like other smooth flows in the area (Fig. 2), becoming tree-scattered, with signs of rumpling of a part-solidified surface, broken slabs, and raised arches of half-formed and filled lava tubes (Fig. 3).
The inner ceilings of these have wonderful ‘pluck and drip’ lava, which are extremely sharp and spiky. Some of these are bent sideways, indicating the direction of flow of the lava (Figs. 4 and 5).
There are also many tunnel roofs that formed as arches. The thinner ones are prone to sudden collapse, so visitors need to be very careful about where they walk (Fig. 6).
There are several lava trees nearby (see Deposits, Issue 45, Big Island, Hawaii). These are moulds left behind when the lava abruptly drained away, leaving some stuck to the trunks of the swiftly-dying trees. The larger trees generally remained upright, but the smaller ones would be completely burned away. The sites of these trees now form rock mounds from one metre high to towers that are over five metres tall (Fig. 7).
Down the middle of each, there is either the old dead tree remains or an empty rounded hole where the tree used to stand. The great majority of visitors look no further than this, but a few hundred yards away, more of them are visible – dozens and dozens – starting with a scattered few, then a line of them (Fig. 8), then a forest.
Each is fascinating and unique: many clearly show the direction of the flow, where the surface rumpled and folded on the upstream side, and trailed away downstream, like a scarf in the wind (Fig. 9).
Others have been raised up a metre or two by pressure from beneath, like toothpaste being squeezed out of a tube (Fig. 10). This is a place where you can spend hours exploring – it’s a fantasy forest.
The southern edge of the flow is marked by a 10m-high cliff, the Koa’e Scarp (Fig. 11). It is a reverse fault cliff in which the land on the uphill side sank in relation to the south side, so the cliff faces away from the sea. For much of its length, the 1973 lava didn’t actually reach this cliff, but it did in some places.
Returning towards the road along the northern edge of the flow, there is one of the fissures that the lava erupted from. From a simple split in the ground, the lava spat, propelled a few metres upwards by the expanding gases within it. Falling back, the gobs of lava built up into a ridge that snakes along the edge of the flow, reaching perhaps four metres high in places, but mostly less than that (Fig. 12).
Where the spatter continued to erupt, it built higher ridges and mounds known as ‘ramparts’ (Fig. 13).
3.2 miles: Pauahi Crater
There is a large lay-by here, and it is well sign-posted for the November 1979 lava flow and the Pauahi Crater. The overlook platform is ideally placed for the view down the length of the crater, which is notable for the relative lack of vegetation enshrouding the walls, making it visible in its entirety (Fig. 14).
Pauahi is a relatively large, elongated, collapse crater. Measuring over 600m by 400m, it was originally formed by two separate collapse craters that coalesced and subsided to 100m deep in a series of at least three phases.
In May 1973, an eruption inside the collapse pit partly-filled the crater, but the lava drained away after a short time (Fig. 15), leaving the edges of the lake surface stranded, forming what is known as a ‘bathtub rim’.
This was followed in November and December 1973 by another eruption, which began violently, then petered out over the next month (Fig. 16).
It left flows and pools across the crater floor. These are a tiring walk away and better flows can be seen more easily elsewhere. The disturbance to the ground resulted in a series of en echelon fissures stretching from the west, through the crater and east towards Mauna Ulu. The 1979 eruption, which this site is known for, lasted only one day, but made a lasting impression on the landscape and Hawaiian culture. Offerings to the spirits (Ho’okupu) are often seen here, wrapped in Tī leaves. The name Pauahi means ‘destroyed by fire’ – perhaps a little ironic in a land that has been entirely created by fire.
3.2 miles: Pauahi spatter ridge
Other features of the eruptions are seen close by, most noticeably, the spatter ridge, which is visited from the same large lay-by as the crater. This spatter ridge is much more impressive than the one at Hi’iaka. They occurred at the same time and were part of the same system of fissures, associated with the nearby, much larger, peak of Mauna Ulu. As regards dating, various sources, including several video footages, ascribe this eruption to 1973, rather than 1979.
The Pauahi fissure erupted along a length of several hundred metres (Fig. 17), building up into truly ‘rampart’ size, six and seven metres high (Fig. 18).
Some sections are even more massive, with open ‘blow holes’ that the lava spurted from and often dripped back into (Figs. 19 and 20).
In the vicinity, there are also patches where the multiple fissuring of the ground has caused the whole surface to be fractured into loose blocks (Fig. 21).
Of the several low lava tubes hereabouts, one is especially good and can be crawled into – with care (Fig. 22).
In the next article, we continue our road trip …
|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.|
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.