There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track. Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.
Pahoehoe, A’a, Pele’s Tears and Pele’s Hair
It is obvious to even the most causal observer that various lava formations and lava fields of Hawaii display two distinctly different types of lava flows. Some flows are very smooth, with obvious, well-preserved flow structures, looking almost like poured taffy that has hardened. Others appear more clunky, clinkery and jagged like a field of sharp boulders and cobbles. These two unique rock types result from two distinctly different types of lava flows, Pahoehoe and A’a.
The onomatopoetic word “pahoehoe” flows across your tongue in the same fashion that pahoehoe lava flows down the volcano. Gelatinous and smooth, it looks a bit like small waves with bulbous, lobate “toes” at the front of the flow. As the advancing lobe cools, a thin crust forms on its surface. This crust is expanded and broken by the pressure of lava flowing in behind, in a continually advancing flow. A distinctive breaking-glass sound is made when that cooling crust fractures, which can be disorienting and surprising at first.
The Hawaiian word “pahoehoe” means “to paddle a canoe vigorously” or “well stirred” and indeed, pahoehoe lava has the look of water being furiously paddled by canoeists, or indeed, of well-stirred poi. These highly fluid pahoehoe flows form from the hottest lava with high dissolved fluid content. As the lava cools and de-gasses, the second kind of flow, a’a lava, is formed from it.
A’a flows travel along as a dense mass of highly viscous lava covered in sharp, broken shards called clinkers. Like a tractor tread, a’a clinkers fall off the advancing front of the flow and are buried as the flow moves forward over them, sounding for all the world like a herd of wild bulls has run amok in the world’s largest china shop.
A’a lava, which cools to great piles of razor sharp clinkers, has given rise to the myth that its name derives from Hawaiian’s walking across the cooled a’a barefoot, wincing and saying “Ah! Ah!” with every cringing step. In fact, the word “a’a” in Hawaiian not only means “to blaze or glow” but also “to dare or challenge”. It is a testament to the toughness of Hawaiian warriors that when choosing the site for a battle field, inevitably they chose to fight on an a’a field—using the razor sharp a’a strewn along the landscape as a weapon in and of itself.
Flows generally emerge from the volcano as pahoehoe and change to a’a as they cool and de-gas or as they are subjected to stress and strain forces. It is especially common to find pahoehoe flows changing to a’a in the midst of a steep drop over a cliff, or when butted-up against an impediment to flow. Like the cucumber becoming a pickle, once pahoehoe turns to a’a, in can never turn back into pahoehoe.
Where fire fountains and geysers of lava occur, Pele’s hair and Pele’s tears will form. Pele’s hair are thin, fiber-like strands of basalt glass pulled and spun from the lava fountain by the blowing wind,. Pele’s tears are the droplet-sized, cooled splashes of basalt glass that from from showering, spraying lava.
All media copyright 2010 by Donald B. MacGowan. All rights reserved.