Free Rice Words (and Others) XXIII
Bill Long 8/30/08
With Terms from Vulcanology, Especially Pahoehoe
The longer I live, the more I realize that true understanding of phenomena comes primarily from patient attention to the words used to describe the material from various fields of human endeavor. When you combine the vocabulary of a field with the procedure or method of a field, and learn both, you are ready to understand and be useful in it.
The 19th-21st centuries have bequeathed to the study of most things, scientific subjects especially, an ever-expanding vocabulary which, if you really apply yourself, is not that difficult to learn--it just takes loads of time. That is, the concepts are not difficult; word mastery is the major task. But once you begin to learn some vocabulary, it is as if you are ushered into the adytum of the temple and the high priests of the field are waiting to welcome you to junior priesthood. Thus, there is nothing like learning words to boost your self-confidence and sense that you, too, can understand and, eventually, contribute to knowledge. Words gets you started on that.
Getting the "Flow" of Pahoehoe (pa HOY HOY)
As with most of my word explorations, this one began innocently enough. I just wanted to understand pahohoe, a word from the freerice.com site. I dutifully looked it up in the OED: "smooth, undulating, or corded volcanic lava." The word was first used in English in 1825, and is still used today in describing lava flows (but it doesn't appear in the Collegiate). Running my eye down the various sentences in the OED definition piqued my curiosity about precisely what this is. It is called "smooth lava," or lava with a "ropy surface." One 1887 quotation talked about pahoehoe as "smooth, hummocky lava." Don't you love that word hummocky? A hummock is not a hammock. A hummock is a "protuberance or boss of earth, rock, etc, usualy conical or dome-shaped, rising above the general level of a surface."
Well, how can something be both hummocky and ropy? How is it smooth and ropy, since almost every rope I know has rimose features? Rather than quickly moving on to the next word or breezing on to "finish" the reading assignment, I thought I would take a moment to follow pahoehoe to see where it would lead me. I learned here that pahoehoe is one of three forms of low viscosity lava flow (there is also high-viscosity flow--a word about that below). They are the " 'a'a, the pahoehoe, and pillow lava." The key to understanding low viscosity lava is to know that it flows as a liquid, reaching out and enveloping or covering everything in its path. Don't you love the image? We have all seen it--the tentacular grasp of the "lava fingers" slowly reaching out and encircling trees, homes, and whatever else is stationary.
Well, pahoehoe (the word is Hawaiian) flow is basaltic lava that has a "smooth, billow, undulating, or ropy surface." The reason it can have so many different surface manifestations is because of the unpredictable movement of lava in the lava tubes under the congealing surface crust. Here is a pahoehoe page from the US Geological Service, with all kinds of photos of different forms of pahoehoe. One sentence in the description his helpful:
"A pahoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust."
Thus, as the lava flows, fed by the undersurface "tubes," it moves in unpredictable and bizarre shapes, which many call "lava sculpture." Some of the coils, for example, that can result from a pahoehoe flow are really arresting--like this one. I am surprised that some person hasn't used these photos as proof that we were invaded millions of eons ago by extraterrestrial shellfish-shaped creatures who not only left their "traces" in this kind of pahoehoe, but who maybe stayed around and are infiltrating government at every level.
Back to planet earth. These pillowy toes of lava are suggestive to the imagination, even though you probably should get out of the way of them... Well, here is some ropy pahoehoe, which is called the "most common surface texture of pahoehoe flows." The ropy surface forms because of the different pace of flow of the crust and beneath-the-crust lava. The surface crust then "behaves like an accordion that is squeezed together--the crust is flexible enough to develop wrinkles or a series of small ridges..." A rugose surface, then. Here is a picture of pahoehoe toes. What you don't want to do with these toes is to play "This little piggy went to market..." It would burn your ass pretty bad, I think.
Clinker and Clinkery
One more word from low viscosity lava--related to the 'a 'a (pronounced "ah-ah"). This low viscosity lava has a "rough, jagged, spiny" or "rubbly" surface. It is not as smooth as the flow of pahoehoe, and the resulting deposit is very hard to walk over. It is also described as having a clinkery surface. Isn't that a great-sounding word? The word clinker is a Dutch-derived word. Originall a clinker was a pale-colored paving brick. In 1850 the word was applied to a mass of hardened volcanic lava in Dana's Geology textbook: "Lava and scoria in immense masses, piled together in the utmost confusion. They are styled clinkers or clinker fields." So, just as we have high-heeled races now, in Russia and other places, why don't we explore the notion of high-heeled races over clinker or clinkery surfaces? I am sure that it would receive the highest viewer rating ever...
Concluding Bonus--One Word on "High Viscosity" Lava
Speaking above of rugose (from the Latin word ruga, which means a wrinkle or fold), we also have much less "smooth" lava, which usually results from the quick congealing of highly viscous lavas (which don't flow as liquid). Let's learn one more word about this before gracefully bowing out. "Highly viscous lavas do not usually flow as liquid, and usually form explosive fragmental ask or tephra deposits." There is a good word--tephra, taken from the Swedish tefra only in 1944. "The author suggests (volcanic) ash or (better) tephra as a collective term for all clastic ejectamenta. Let me give you a slightly longer definition:
"Solid material of all sizes explosively ejected from a volcano into the atmosphere. Tephra is the general term now used by volcanologists for airborne volcanic ejecta of any size."
But I leave you with that word ejectamenta from above--doesn't it just give you all kinds of vivid pictures? Only words will do that...
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